Flat draws: phase 1's solid lists made on the GPU

In frames drawn flat (Metal at render distance 32, Intel Gen11/12 Vulkan),
the render thread walked every phase 1 section's sides each frame to find the
runs of quads that face the eye, then the flat plan copied them into one index
list. Now each section uploads a row once (where its quads start, how Sides
sorted them), and each frame phase 1 pushes one record per section: the GPU
(gpu_lists.wgsl's flatten_sides) finds the same runs as Sides::visible_from and
writes their indices into a call per pass and arena page, drawn indirect.
Phase 2, translucent quads, tiles, mirrors, shader pack terrain and shadows
keep the CPU lists. HORIZON_GPU_LISTS=0 turns it off.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

.gitattributes

@@ -4,3 +4,8 @@ docs/launcher-commands.md text eol=lf
 docs/horizon-ctl-commands.md text eol=lf
 crates/horizon-theme/tokens.css text eol=lf
 docs/api/*-reference.md text eol=lf
+# Generated by `cargo run -p xtask -- mod-api`; `--check` compares them byte for byte.
+crates/horizon-client/src/mod_api/generated.rs linguist-generated=true text eol=lf
+crates/horizon-client/src/mod_api/generated_host.rs linguist-generated=true text eol=lf
+crates/horizon-client/src/game/mod_api_host_generated.rs linguist-generated=true text eol=lf
+crates/horizon-client-render/src/gfx/native_render/generated.rs linguist-generated=true text eol=lf

Cargo.lock

@@ -5120,6 +5120,9 @@ name = "xtask"
 version = "0.1.0"
 dependencies = [
  "horizon-theme",
+ "quote",
+ "serde_json",
+ "syn 2.0.119",
 ]
 
 [[package]]

THIRD_PARTY_NOTICES.md

@@ -91,3 +91,27 @@ licensed under the MIT license:
 > NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 > DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 > OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+## FusionExamples
+
+The tile tables in `crates/horizon-optifine/src/fusion/layout.rs` were read off the connecting
+texture templates (`templates/template <layout>.png`) of
+[FusionExamples](https://github.com/SuperMartijn642/FusionExamples) (at `8c9c56e`), which is
+licensed under the MIT license:
+
+> Copyright (c) 2024 Martijn van den Brand
+>
+> Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+> and associated documentation files (the "Software"), to deal in the Software without
+> restriction, including without limitation the rights to use, copy, modify, merge, publish,
+> distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
+> Software is furnished to do so, subject to the following conditions:
+>
+> The above copyright notice and this permission notice shall be included in all copies or
+> substantial portions of the Software.
+>
+> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
+> BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+> NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+> DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+> OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

crates/horizon-assets/src/resolve.rs

@@ -130,6 +130,26 @@ impl ModelLibrary {
     pub fn resolve(&self, name: &str) -> Result<ResolvedCuboidModel> {
         self.resolve_chain(name, None)
     }
+    /// Whether `name` and every parent it reaches are models of this library,
+    /// with no cycle: `resolve` puts the missing model in for any other.
+    pub fn resolves(&self, name: &str) -> bool {
+        let Ok(mut name) = identifier(name) else {
+            return false;
+        };
+        let mut visited = BTreeSet::new();
+        loop {
+            let Some(model) = self.models.get(&name) else {
+                return false;
+            };
+            if !visited.insert(name.clone()) {
+                return false;
+            }
+            match &model.parent {
+                Some(parent) => name = parent.clone(),
+                None => return true,
+            }
+        }
+    }
     /// `name`'s resolved model with a virtual child in front of it that has
     /// only `textures`: the child's slots win, and `#references` anywhere in
     /// the chain re-bind through them (so `builtin/generated`'s
@@ -529,4 +549,23 @@ mod tests {
             "minecraft:missingno"
         );
     }
+    #[test]
+    fn a_model_resolves_only_with_its_whole_parent_chain() {
+        let library = library(&[
+            ("item/generated", GENERATED),
+            (
+                "item/stick",
+                r#"{"parent":"item/generated","textures":{"layer0":"item/stick"}}"#,
+            ),
+            ("item/orphan", r#"{"parent":"item/gone"}"#),
+            ("item/a", r#"{"parent":"item/b"}"#),
+            ("item/b", r#"{"parent":"item/a"}"#),
+        ]);
+        assert!(library.resolves("item/stick"));
+        assert!(library.resolves("minecraft:item/stick"));
+        assert!(!library.resolves("item/absent"));
+        assert!(!library.resolves("item/orphan"));
+        assert!(!library.resolves("item/a"));
+        assert!(!library.resolves("Item/Stick"));
+    }
 }

crates/horizon-client-core/src/lang.rs

@@ -3,6 +3,7 @@
 //! from `pack.mcmeta` `language` sections, and a process-wide current
 //! language used by every screen.
 use std::{
+    cell::RefCell,
     collections::{BTreeMap, HashMap},
     sync::{
         Arc, RwLock,
@@ -34,6 +35,15 @@ pub struct Language {
 pub const DEFAULT: &str = "en_us";
 
 static CURRENT: RwLock<Option<Arc<Language>>> = RwLock::new(None);
+/// A language that only the calling thread sees, and the keys it was asked for and did not have
+/// (`scoped`).
+struct Scope {
+    language: Arc<Language>,
+    missed: Vec<String>,
+}
+thread_local! {
+    static SCOPE: RefCell<Option<Scope>> = const { RefCell::new(None) };
+}
 /// The current language's `bidirectional`, read for every drawn string.
 static BIDIRECTIONAL: AtomicBool = AtomicBool::new(false);
 
@@ -254,8 +264,50 @@ pub fn set(language: Language) {
     *CURRENT.write().unwrap_or_else(|e| e.into_inner()) = Some(Arc::new(language));
 }
 pub fn current() -> Option<Arc<Language>> {
+    if let Some(language) = SCOPE.with(|s| s.borrow().as_ref().map(|s| s.language.clone())) {
+        return Some(language);
+    }
     CURRENT.read().unwrap_or_else(|e| e.into_inner()).clone()
 }
+/// Runs `f` with `language` as the current language of this thread only, and returns what it
+/// returned with the keys `get` and `get_or` looked up and `language` did not have, in the order
+/// asked and without repeats. Nothing is set process-wide, so a test can draw a screen in another
+/// language while the tests beside it read theirs. Scopes nest: the inner one wins, and the outer
+/// one's misses do not include the inner one's. For tests: `bidirectional` stays the process-wide
+/// language's.
+pub fn scoped<R>(language: Language, f: impl FnOnce() -> R) -> (R, Vec<String>) {
+    /// Puts the outer scope back, also when `f` panics.
+    struct Restore(Option<Scope>);
+    impl Drop for Restore {
+        fn drop(&mut self) {
+            SCOPE.with(|s| *s.borrow_mut() = self.0.take());
+        }
+    }
+    let outer = SCOPE.with(|s| {
+        s.borrow_mut().replace(Scope {
+            language: Arc::new(language),
+            missed: Vec::new(),
+        })
+    });
+    let _restore = Restore(outer);
+    let result = f();
+    let missed = SCOPE.with(|s| {
+        s.borrow_mut()
+            .as_mut()
+            .map(|s| std::mem::take(&mut s.missed))
+    });
+    (result, missed.unwrap_or_default())
+}
+/// `key` was asked for in a `scoped` language that has no text for it.
+fn missed(key: &str) {
+    SCOPE.with(|s| {
+        if let Some(scope) = s.borrow_mut().as_mut()
+            && !scope.missed.iter().any(|m| m == key)
+        {
+            scope.missed.push(key.to_owned());
+        }
+    });
+}
 /// `ClientLanguage.defaultRightToLeft` of the current language.
 pub fn bidirectional() -> bool {
     BIDIRECTIONAL.load(Ordering::Relaxed)
@@ -267,13 +319,19 @@ pub fn code() -> String {
 pub fn get(key: &str) -> String {
     current()
         .and_then(|l| l.get(key).map(str::to_owned))
-        .unwrap_or_else(|| key.to_owned())
+        .unwrap_or_else(|| {
+            missed(key);
+            key.to_owned()
+        })
 }
 /// The translation, or `fallback` when the key is missing.
 pub fn get_or(key: &str, fallback: &str) -> String {
     current()
         .and_then(|l| l.get(key).map(str::to_owned))
-        .unwrap_or_else(|| fallback.to_owned())
+        .unwrap_or_else(|| {
+            missed(key);
+            fallback.to_owned()
+        })
 }
 pub fn has(key: &str) -> bool {
     current().is_some_and(|l| l.get(key).is_some())
@@ -350,6 +408,52 @@ mod tests {
         );
     }
 
+    #[test]
+    fn a_scoped_language_is_the_calling_threads_and_reports_what_it_lacks() {
+        let empty = Mem(HashMap::new());
+        let outside = code();
+        let ((german, english_only, fallback, elsewhere), missed) =
+            scoped(Language::load(&[&empty], "de_de"), || {
+                (
+                    get("horizon.osk.close"),
+                    get("horizon.no_such_key"),
+                    get_or("horizon.no_fallback", "English"),
+                    // Another thread keeps the process-wide language.
+                    std::thread::spawn(code).join().unwrap(),
+                )
+            });
+        assert_eq!(german, "Schließen");
+        assert_eq!(english_only, "horizon.no_such_key");
+        assert_eq!(fallback, "English");
+        assert_eq!(elsewhere, outside);
+        assert_eq!(missed, ["horizon.no_such_key", "horizon.no_fallback"]);
+        // The scope ends with its closure.
+        assert_eq!(code(), outside);
+    }
+
+    #[test]
+    fn scopes_nest_and_end_when_their_closure_panics() {
+        let empty = Mem(HashMap::new());
+        let outside = code();
+        let (inner, missed) = scoped(Language::load(&[&empty], "fr_fr"), || {
+            let (inner, inner_missed) = scoped(Language::load(&[&empty], "pl_pl"), || {
+                (code(), get("horizon.inner_miss"))
+            });
+            assert_eq!(inner_missed, ["horizon.inner_miss"]);
+            assert_eq!(code(), "fr_fr");
+            inner.0
+        });
+        assert_eq!(inner, "pl_pl");
+        assert!(missed.is_empty());
+        let panicked = std::panic::catch_unwind(|| {
+            scoped(Language::load(&[&Mem(HashMap::new())], "de_de"), || {
+                panic!("a test failed inside a scope")
+            })
+        });
+        assert!(panicked.is_err());
+        assert_eq!(code(), outside);
+    }
+
     /// `crates/horizon-client/assets/horizon/lang`, where Horizon's own strings live.
     fn bundled_dir() -> std::path::PathBuf {
         std::path::Path::new(env!("CARGO_MANIFEST_DIR"))

crates/horizon-client-input/src/interaction_input.rs

@@ -51,6 +51,10 @@ impl InteractionInput {
     pub fn press(&mut self, button: Button) {
         self.clicks[button as usize] += 1;
     }
+    /// Whether a click waits for the next tick.
+    pub fn has_clicks(&self) -> bool {
+        self.clicks.iter().any(|&c| c > 0)
+    }
 
     pub fn tick(&mut self, world: &mut impl InteractionWorld, attack_down: bool, use_down: bool) {
         let [attack, use_item, pick] = std::mem::take(&mut self.clicks);

crates/horizon-client-render/src/block_entities.rs

@@ -46,6 +46,7 @@ pub enum Ticking {
 #[derive(Default)]
 pub struct BlockEntities {
     map: HashMap<Pos, BlockEntity>,
+    attachments: HashMap<Pos, horizon_world::attachments::Attachments>,
     /// `Level.blockEntityTickers`: positions and the slot each was given.
     tickers: Arc<Vec<(Pos, u32)>>,
     /// `LevelChunk.tickersInLevel`: the live slot of each ticking position.
@@ -84,6 +85,18 @@ pub struct BlockEntities {
     /// which leaves out a mod block whose template has none. One taken out
     /// (`take`) stays listed until `put` or `remove`.
     mods: FxHashMap<(i32, i32), FxHashSet<Pos>>,
+    /// The positions of the block entities that draw a bounding box (structure and test
+    /// instance blocks, `shows_box`), so a frame looks at them without scanning the map.
+    /// Like `mods`, one taken out stays listed until `put` or `remove`.
+    boxes: FxHashSet<Pos>,
+}
+
+/// A structure or test instance block: the block entities whose box the frame may draw.
+fn shows_box(entity: &BlockEntity) -> bool {
+    matches!(
+        entity,
+        BlockEntity::StructureBlock(_) | BlockEntity::TestInstanceBlock(_)
+    )
 }
 
 fn chunk_of((x, _, z): Pos) -> (i32, i32) {
@@ -220,11 +233,53 @@ impl BlockEntities {
         self.pending.remove(pos);
     }
 
+    /// Attachment map for a live block entity.
+    pub fn attachments_mut(
+        &mut self,
+        pos: Pos,
+    ) -> Option<&mut horizon_world::attachments::Attachments> {
+        if !self.map.contains_key(&pos) && !self.out.contains(&pos) {
+            return None;
+        }
+        Some(self.attachments.entry(pos).or_default())
+    }
+    /// Attachment maps in a loaded chunk, for a save snapshot.
+    pub fn chunk_attachments(
+        &self,
+        x: i32,
+        z: i32,
+    ) -> Vec<(Pos, horizon_world::attachments::Attachments)> {
+        self.attachments
+            .iter()
+            .filter(|(p, _)| p.0 >> 4 == x && p.2 >> 4 == z)
+            .map(|(p, data)| (*p, data.clone()))
+            .collect()
+    }
+    /// Restore a loaded block entity's attachment map.
+    pub fn restore_attachments(&mut self, pos: Pos, data: horizon_world::attachments::Attachments) {
+        if self.map.contains_key(&pos) {
+            self.attachments.insert(pos, data);
+        }
+    }
     /// Whether any mod block entity is in the map: until one is, a block change
     /// never looks one up (`LevelAccess::has_mod_block_entity`).
     pub fn has_mods(&self) -> bool {
         !self.mods.is_empty()
     }
+    /// The structure and test instance blocks (a frame draws their boxes), in no order.
+    pub fn boxes(&self) -> impl Iterator<Item = (&Pos, &BlockEntity)> {
+        self.boxes
+            .iter()
+            .filter_map(|pos| Some((pos, self.map.get(pos)?)))
+    }
+    /// Keeps `pos` listed in `boxes` exactly while `entity` shows a box.
+    fn note_box(&mut self, pos: Pos, entity: Option<&BlockEntity>) {
+        if entity.is_some_and(shows_box) {
+            self.boxes.insert(pos);
+        } else {
+            self.boxes.remove(&pos);
+        }
+    }
     /// The mod block entities within `radius` blocks of `x`, `z` (by chunk, so
     /// far ones are skipped whole; the caller checks each distance).
     pub fn mods_near(&self, x: f64, z: f64, radius: f64) -> impl Iterator<Item = &Pos> {
@@ -248,12 +303,28 @@ impl BlockEntities {
     }
     /// `LevelChunk.setBlockEntity` (+ `addAndRegisterBlockEntity`): a new
     /// block entity may get a slot; one replacing another keeps its slot.
+    /// One of the same type rewrites it in place (a jukebox taking a disc,
+    /// `/data merge block`), where vanilla keeps the object, so its
+    /// attachments stay; any other replacement starts them over.
     pub fn insert(&mut self, pos: Pos, entity: BlockEntity) -> Option<BlockEntity> {
         let new_is_mod = matches!(entity, BlockEntity::Mod(_));
+        let same_type = |old: &BlockEntity| match (old, &entity) {
+            (BlockEntity::Mod(old), BlockEntity::Mod(new)) => old.id == new.id,
+            (old, new) => std::mem::discriminant(old) == std::mem::discriminant(new),
+        };
+        if !self.map.get(&pos).is_some_and(same_type) {
+            self.attachments.remove(&pos);
+        }
+        let new_box = shows_box(&entity);
         let old = self.map.insert(pos, entity);
         if old.is_none() {
             self.add(pos);
         }
+        if new_box {
+            self.boxes.insert(pos);
+        } else if old.as_ref().is_some_and(shows_box) {
+            self.boxes.remove(&pos);
+        }
         if new_is_mod {
             self.mods.entry(chunk_of(pos)).or_default().insert(pos);
         } else if matches!(old, Some(BlockEntity::Mod(_))) {
@@ -275,15 +346,20 @@ impl BlockEntities {
         if absent && matches!(entity, BlockEntity::Mod(_)) {
             self.mods.entry(chunk_of(pos)).or_default().insert(pos);
         }
+        if absent && shows_box(entity) {
+            self.boxes.insert(pos);
+        }
         entity
     }
     /// `LevelChunk.removeBlockEntity`: the block entity and its slot.
     pub fn remove(&mut self, pos: &Pos) -> Option<BlockEntity> {
+        self.attachments.remove(pos);
         self.cancel(pos);
         let removed = self.map.remove(pos);
         if matches!(removed, Some(BlockEntity::Mod(_))) {
             forget_mod(&mut self.mods, *pos);
         }
+        self.boxes.remove(pos);
         removed
     }
     /// The block entity at `pos`, out of the map for a while: its slot stays
@@ -301,6 +377,7 @@ impl BlockEntities {
         if matches!(entity, BlockEntity::Mod(_)) {
             self.mods.entry(chunk_of(pos)).or_default().insert(pos);
         }
+        self.note_box(pos, Some(&entity));
         if self.map.insert(pos, entity).is_none()
             && !self.live.contains_key(&pos)
             && !self.pending.contains_key(&pos)
@@ -311,21 +388,30 @@ impl BlockEntities {
     /// Removes the block entities `keep` refuses, and their slots
     /// (`clearAllBlockEntities` of unloaded chunks).
     pub fn retain(&mut self, mut keep: impl FnMut(&Pos, &mut BlockEntity) -> bool) {
-        let (live, pending, freed) = (&mut self.live, &mut self.pending, &mut self.freed);
-        let mods = &mut self.mods;
+        let (live, pending, freed, attachments) = (
+            &mut self.live,
+            &mut self.pending,
+            &mut self.freed,
+            &mut self.attachments,
+        );
+        let (mods, boxes) = (&mut self.mods, &mut self.boxes);
         self.map.retain(|p, e| {
             let kept = keep(p, e);
             if !kept {
+                attachments.remove(p);
                 *freed |= live.remove(p).is_some();
                 pending.remove(p);
                 forget_mod(mods, *p);
+                boxes.remove(p);
             }
             kept
         });
     }
     pub fn clear(&mut self) {
+        self.attachments.clear();
         self.map.clear();
         self.mods.clear();
+        self.boxes.clear();
         self.tickers = Arc::default();
         self.live.clear();
         self.added.clear();
@@ -342,7 +428,9 @@ impl BlockEntities {
     pub fn load_chunk(&mut self, entities: Vec<(Pos, BlockEntity)>) {
         let order = chunk_map_order(entities.iter().map(|(p, _)| *p));
         for (p, e) in entities {
+            self.attachments.remove(&p);
             let new_is_mod = matches!(e, BlockEntity::Mod(_));
+            self.note_box(p, Some(&e));
             let old = self.map.insert(p, e);
             if old.is_some() {
                 self.replaced.insert(p);
@@ -476,6 +564,52 @@ mod tests {
         b.clear();
         assert!(near(&b, 200.0, 0.0, 8.0).is_empty());
     }
+    #[test]
+    fn attachments_follow_block_entity_lifetime() {
+        use horizon_world::attachments::AttachmentType;
+        let ty = AttachmentType {
+            namespace: "test",
+            name: "value",
+            default: || 0,
+            codec: None,
+            copy_on_death: false,
+        };
+        let p = (1, 64, 2);
+        let mut entities = level();
+        assert!(entities.attachments_mut(p).is_none());
+        entities.insert(p, hopper());
+        entities.attachments_mut(p).unwrap().set(&ty, 4).unwrap();
+        let held = entities.take(&p).unwrap();
+        entities.put(p, held);
+        assert_eq!(entities.attachments_mut(p).unwrap().get(&ty), Ok(4));
+        entities.insert(p, hopper());
+        assert_eq!(entities.attachments_mut(p).unwrap().get(&ty), Ok(4));
+        let machine = |id: &str| {
+            BlockEntity::Mod(Box::new(
+                crate::chunk::block_entity::ModBlockEntityFields {
+                    id: id.into(),
+                    ..Default::default()
+                }
+                .into(),
+            ))
+        };
+        entities.insert(p, machine("test:a"));
+        assert_eq!(entities.attachments_mut(p).unwrap().get(&ty), Ok(0));
+        entities.attachments_mut(p).unwrap().set(&ty, 4).unwrap();
+        entities.insert(p, machine("test:a"));
+        assert_eq!(entities.attachments_mut(p).unwrap().get(&ty), Ok(4));
+        entities.insert(p, machine("test:b"));
+        assert_eq!(entities.attachments_mut(p).unwrap().get(&ty), Ok(0));
+        entities.attachments_mut(p).unwrap().set(&ty, 4).unwrap();
+        entities.remove(&p);
+        entities.insert(p, hopper());
+        assert_eq!(entities.attachments_mut(p).unwrap().get(&ty), Ok(0));
+        entities.attachments_mut(p).unwrap().set(&ty, 5).unwrap();
+        entities.retain(|_, _| false);
+        entities.insert(p, hopper());
+        assert_eq!(entities.attachments_mut(p).unwrap().get(&ty), Ok(0));
+    }
+
     #[test]
     fn slots_follow_vanilla_lifecycle() {
         let mut b = level();
@@ -560,4 +694,43 @@ mod tests {
         b.state_changed(p, 2, 1);
         assert_eq!(order(&mut b, &s), [q, p]);
     }
+
+    #[test]
+    fn boxes_list_exactly_the_structure_and_test_blocks() {
+        let test_block = || BlockEntity::TestInstanceBlock(Box::default());
+        let listed = |b: &BlockEntities| {
+            let mut v: Vec<Pos> = b.boxes().map(|(p, _)| *p).collect();
+            v.sort();
+            v
+        };
+        let mut b = level();
+        let (p, q, r) = ((0, 0, 0), (1, 0, 0), (2, 0, 0));
+        b.insert(p, test_block());
+        b.insert(q, hopper());
+        assert_eq!(listed(&b), [p]);
+        // Replaced by another kind, and back.
+        b.insert(p, hopper());
+        assert_eq!(listed(&b), []);
+        b.insert(q, test_block());
+        b.get_or_insert_with(r, test_block);
+        assert_eq!(listed(&b), [q, r]);
+        // Taken out: not shown until put back; put back as another kind: gone.
+        let taken = b.take(&q).unwrap();
+        assert_eq!(listed(&b), [r]);
+        b.put(q, taken);
+        assert_eq!(listed(&b), [q, r]);
+        let taken = b.take(&r).unwrap();
+        drop(taken);
+        b.put(r, hopper());
+        assert_eq!(listed(&b), [q]);
+        b.remove(&q);
+        assert_eq!(listed(&b), []);
+        b.load_chunk(vec![(p, test_block()), (q, hopper())]);
+        assert_eq!(listed(&b), [p]);
+        b.retain(|pos, _| *pos != p);
+        assert_eq!(listed(&b), []);
+        b.insert(r, test_block());
+        b.clear();
+        assert!(b.boxes.is_empty());
+    }
 }

crates/horizon-client-render/src/block_entity_cem.rs

@@ -0,0 +1,630 @@
+//! OptiFine custom entity models over the block entities' models (`block_entity_render`'s
+//! `MODELS`): `chest.jem`, `shulker_box.jem`, `banner.jem`, `bell.jem`, `head_zombie.jem`... (the
+//! "Block entity name" table of OptiFine's `cem_model.txt`, and Entity Model Features' one-file
+//! `banner`), found and read as the mobs' are ([`horizon_optifine::cem::files`]). Each entry
+//! replaces or joins the boxes of the vanilla part it names and takes its `scale`; animations
+//! don't run yet. A `.jem`'s texture paints the models it reshapes instead of vanilla's when the
+//! atlas has it.
+//!
+//! An entry's part is OptiFine's name for it, else the vanilla part's own name. Trapped and
+//! ender chests take only their own file, and copper chests (no CEM name) keep vanilla's chest.
+//! Lectern and enchanting-table books take theirs, else `book`. Signs, hanging signs and beds are
+//! block models here, so their files are not read; copper golem statues have no CEM name.
+
+use crate::block_entity_render::ModelPart;
+use horizon_optifine::cem::{
+    files::{atlas_name, jem_files, load_jem},
+    model::{Bone, EntityModel},
+};
+use std::{
+    collections::{BTreeMap, HashMap, HashSet},
+    path::Path,
+};
+
+/// One model the renderer draws, the CEM names that reshape it, best first, and OptiFine's
+/// names for its vanilla parts.
+struct Target {
+    key: &'static str,
+    /// The vanilla model it starts from: `key` itself, or the one a block the renderer tells
+    /// apart shares (a trapped chest's is the chest's).
+    base: &'static str,
+    names: &'static [&'static str],
+    parts: &'static [(&'static str, &'static str)],
+}
+
+const CHEST: &[(&str, &str)] = &[
+    ("root", "root"),
+    ("base", "bottom"),
+    ("lid", "lid"),
+    ("knob", "lock"),
+];
+const SHULKER: &[(&str, &str)] = &[("root", "root"), ("base", "base"), ("lid", "lid")];
+const BANNER: &[(&str, &str)] = &[("stand", "pole"), ("top", "bar")];
+const FLAG: &[(&str, &str)] = &[("slate", "flag")];
+const HEAD: &[(&str, &str)] = &[("root", "root"), ("head", "head")];
+const DRAGON: &[(&str, &str)] = &[("root", "root"), ("head", "head"), ("jaw", "jaw")];
+const PIGLIN: &[(&str, &str)] = &[
+    ("root", "root"),
+    ("head", "head"),
+    ("left_ear", "left_ear"),
+    ("right_ear", "right_ear"),
+];
+const BELL: &[(&str, &str)] = &[
+    ("root", "root"),
+    ("body", "bell_body"),
+    ("base", "bell_base"),
+];
+const BOOK: &[(&str, &str)] = &[
+    ("root", "root"),
+    ("cover_right", "right_lid"),
+    ("cover_left", "left_lid"),
+    ("pages_right", "right_pages"),
+    ("pages_left", "left_pages"),
+    ("flipping_page_right", "flip_page1"),
+    ("flipping_page_left", "flip_page2"),
+    ("book_spine", "seam"),
+];
+const POT_BASE: &[(&str, &str)] = &[("neck", "neck"), ("top", "top"), ("bottom", "bottom")];
+const POT_SIDES: &[(&str, &str)] = &[
+    ("front", "front"),
+    ("back", "back"),
+    ("left", "left"),
+    ("right", "right"),
+];
+
+const fn model(
+    key: &'static str,
+    names: &'static [&'static str],
+    parts: &'static [(&'static str, &'static str)],
+) -> Target {
+    Target {
+        key,
+        base: key,
+        names,
+        parts,
+    }
+}
+const fn copy(
+    key: &'static str,
+    base: &'static str,
+    names: &'static [&'static str],
+    parts: &'static [(&'static str, &'static str)],
+) -> Target {
+    Target {
+        key,
+        base,
+        names,
+        parts,
+    }
+}
+
+/// In order: a copy comes after its base.
+const TARGETS: &[Target] = &[
+    model("chest", &["chest"], CHEST),
+    model("double_chest_left", &["chest_left"], CHEST),
+    model("double_chest_right", &["chest_right"], CHEST),
+    copy("trapped_chest", "chest", &["trapped_chest"], CHEST),
+    copy(
+        "trapped_chest_left",
+        "double_chest_left",
+        &["trapped_chest_left"],
+        CHEST,
+    ),
+    copy(
+        "trapped_chest_right",
+        "double_chest_right",
+        &["trapped_chest_right"],
+        CHEST,
+    ),
+    copy("ender_chest", "chest", &["ender_chest"], CHEST),
+    model("shulker_box", &["shulker_box"], SHULKER),
+    model("standing_banner", &["banner_base", "banner"], BANNER),
+    model("wall_banner", &["banner_base", "banner"], BANNER),
+    model("standing_banner_flag", &["banner_flag", "banner"], FLAG),
+    model("wall_banner_flag", &["banner_flag", "banner"], FLAG),
+    model("skeleton_skull", &["head_skeleton"], HEAD),
+    model("wither_skeleton_skull", &["head_wither_skeleton"], HEAD),
+    model("zombie_head", &["head_zombie"], HEAD),
+    model("creeper_head", &["head_creeper"], HEAD),
+    model("dragon_skull", &["head_dragon"], DRAGON),
+    model("piglin_head", &["head_piglin"], PIGLIN),
+    model("player_head", &["head_player"], HEAD),
+    model("bell", &["bell"], BELL),
+    model("book", &["enchanting_book", "book"], BOOK),
+    copy("lectern_book", "book", &["lectern_book", "book"], BOOK),
+    model("conduit_shell", &["conduit"], &[("base", "shell")]),
+    model("conduit_cage", &["conduit"], &[("cage", "shell")]),
+    model("conduit_wind", &["conduit"], &[("wind", "wind")]),
+    model("conduit_eye", &["conduit"], &[("eye", "eye")]),
+    model("decorated_pot_base", &["decorated_pot"], POT_BASE),
+    model("decorated_pot_sides", &["decorated_pot"], POT_SIDES),
+];
+
+/// Every model, reshaped or vanilla's, and the atlas names of the `.jem` textures by model.
+pub type Reshaped = (
+    HashMap<&'static str, ModelPart>,
+    HashMap<&'static str, String>,
+);
+
+/// The models the packs under `root` reshape, over `vanilla`'s; None when no block entity has
+/// a `.jem` there.
+pub fn reshape(root: &Path, vanilla: &HashMap<&'static str, ModelPart>) -> Option<Reshaped> {
+    let (reshaped, unused) = reshape_all(root, vanilla)?;
+    for (path, part) in unused {
+        log::warn!("Horizon: custom entity model {path}: no part {part}");
+    }
+    Some(reshaped)
+}
+
+/// [`reshape`]'s models, and each file's entries whose part none of the models it reshapes has.
+fn reshape_all(
+    root: &Path,
+    vanilla: &HashMap<&'static str, ModelPart>,
+) -> Option<(Reshaped, Vec<(String, String)>)> {
+    let files = jem_files(root);
+    let named = |t: &Target| t.names.iter().any(|n| files.contains_key(*n));
+    if !TARGETS.iter().any(named) {
+        return None;
+    }
+    let mut models = vanilla.clone();
+    let mut textures = HashMap::new();
+    let mut reshaped = HashSet::new();
+    // Each file parsed once; which of its entries found a part in some model.
+    let mut parsed: HashMap<&str, Option<EntityModel>> = HashMap::new();
+    let mut used: BTreeMap<&str, Vec<bool>> = BTreeMap::new();
+    for t in TARGETS {
+        let Some(model) = vanilla.get(t.base) else {
+            continue;
+        };
+        let found = t
+            .names
+            .iter()
+            .flat_map(|name| files.get(*name).into_iter().flatten())
+            .map(String::as_str)
+            .find(|&path| {
+                parsed
+                    .entry(path)
+                    .or_insert_with(|| load_jem(root, path))
+                    .is_some()
+            });
+        let Some(path) = found else {
+            // A copy of a reshaped base that has no file of its own stays vanilla.
+            if t.key != t.base && reshaped.contains(t.base) {
+                models.insert(t.key, model.clone());
+            }
+            continue;
+        };
+        let Some(Some(jem)) = parsed.get(path) else {
+            continue;
+        };
+        let mut out = model.clone();
+        let hits = apply(&mut out, jem, t.parts);
+        // A file shared by several models (the conduit's, the pot's) paints only the models
+        // it reshapes: vanilla geometry keeps its own texture's layout.
+        let reshapes = hits.iter().any(|hit| *hit);
+        let marks = used
+            .entry(path)
+            .or_insert_with(|| vec![false; jem.parts.len()]);
+        for (mark, hit) in marks.iter_mut().zip(hits) {
+            *mark |= hit;
+        }
+        models.insert(t.key, out);
+        reshaped.insert(t.key);
+        if reshapes && let Some(texture) = jem.texture.as_deref().and_then(atlas_name) {
+            textures.insert(t.key, texture);
+        }
+    }
+    let mut unused = Vec::new();
+    for (path, marks) in &used {
+        let Some(Some(jem)) = parsed.get(path) else {
+            continue;
+        };
+        for (p, _) in jem.parts.iter().zip(marks).filter(|(_, hit)| !**hit) {
+            unused.push(((*path).to_owned(), p.part.clone()));
+        }
+    }
+    Some(((models, textures), unused))
+}
+
+/// `jem`'s entries on `model`, OptiFine's part names read through `parts`, else as the vanilla
+/// part's own name: a replacing entry clears its part's boxes, and each joins the part as a child
+/// `cem#<n>`. Which entries found their part.
+fn apply(model: &mut ModelPart, jem: &EntityModel, parts: &[(&str, &str)]) -> Vec<bool> {
+    let mut count = 0;
+    let mut hits = Vec::with_capacity(jem.parts.len());
+    for p in &jem.parts {
+        let mapped = parts.iter().find(|(of, _)| *of == p.part).map(|&(_, v)| v);
+        let target = match mapped {
+            Some(vanilla) if find_mut(model, vanilla).is_some() => vanilla,
+            _ => p.part.as_str(),
+        };
+        let Some(node) = find_mut(model, target) else {
+            hits.push(false);
+            continue;
+        };
+        if !p.attach {
+            node.polygons.clear();
+        }
+        let (name, mut bone) = part(&p.bone, &mut count);
+        bone.pose[6..9].fill(p.scale);
+        node.children.push((name, bone));
+        hits.push(true);
+    }
+    hits
+}
+
+/// The model itself for `root`, else its first part named `name`, depth first.
+fn find_mut<'a>(model: &'a mut ModelPart, name: &str) -> Option<&'a mut ModelPart> {
+    fn child<'a>(part: &'a mut ModelPart, name: &str) -> Option<&'a mut ModelPart> {
+        part.children.iter_mut().find_map(|(n, c)| {
+            if n.as_str() == name {
+                Some(c)
+            } else {
+                child(c, name)
+            }
+        })
+    }
+    if name == "root" {
+        return Some(model);
+    }
+    child(model, name)
+}
+
+/// A baked bone as a model part, named `cem#<n>`: unique in the model, so no vanilla pose
+/// change by name reaches it.
+fn part(bone: &Bone, count: &mut usize) -> (String, ModelPart) {
+    let name = format!("cem#{count}");
+    *count += 1;
+    let [x, y, z] = bone.pivot;
+    let [rx, ry, rz] = bone.rotation;
+    let out = ModelPart {
+        pose: [x, y, z, rx, ry, rz, 1.0, 1.0, 1.0],
+        polygons: bone.quads.iter().map(|q| q.vertices).collect(),
+        children: bone.children.iter().map(|c| part(c, count)).collect(),
+    };
+    (name, out)
+}
+
+#[cfg(test)]
+pub(crate) mod tests {
+    use super::*;
+    use std::{collections::BTreeSet, fs};
+
+    /// A part with one face and `children`.
+    pub(crate) fn plane(children: Vec<(&str, ModelPart)>) -> ModelPart {
+        ModelPart {
+            pose: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 1.0, 1.0],
+            polygons: vec![[[0.0; 5]; 4]],
+            children: children
+                .into_iter()
+                .map(|(n, c)| (n.to_owned(), c))
+                .collect(),
+        }
+    }
+    pub(crate) fn chest() -> ModelPart {
+        let mut root = plane(vec![
+            ("bottom", plane(vec![])),
+            ("lid", plane(vec![])),
+            ("lock", plane(vec![])),
+        ]);
+        root.polygons.clear();
+        root
+    }
+    pub(crate) const BOX: &str =
+        r#""boxes": [{"coordinates": [0, 0, 0, 1, 1, 1], "textureOffset": [0, 0]}]"#;
+    /// A fresh pack folder named for `test`, holding `files` under `assets/minecraft/`.
+    pub(crate) fn pack(test: &str, files: &[(&str, String)]) -> std::path::PathBuf {
+        let root =
+            std::env::temp_dir().join(format!("horizon-be-cem-{test}-{}", std::process::id()));
+        let _ = fs::remove_dir_all(&root);
+        for (path, text) in files {
+            let path = root.join("assets/minecraft").join(path);
+            fs::create_dir_all(path.parent().unwrap()).unwrap();
+            fs::write(path, text).unwrap();
+        }
+        root
+    }
+    /// A `.jem` replacing each of `parts` with one box.
+    fn jem(parts: &[&str]) -> String {
+        let entries: Vec<_> = parts
+            .iter()
+            .map(|p| format!(r#"{{"part": "{p}", {BOX}}}"#))
+            .collect();
+        format!(r#"{{"models": [{}]}}"#, entries.join(", "))
+    }
+    /// A `.jem` replacing each of `parts` with a box of its own: the `i`th is `i + 1` pixels
+    /// deep, so a part that took another entry's box shows.
+    fn jem_sized(parts: &[&str]) -> String {
+        let entries: Vec<_> = parts
+            .iter()
+            .enumerate()
+            .map(|(i, p)| {
+                let depth = i + 1;
+                format!(
+                    r#"{{"part": "{p}", "boxes": [{{"coordinates": [0, 0, 0, 1, 1, {depth}], "textureOffset": [0, 0]}}]}}"#
+                )
+            })
+            .collect();
+        format!(r#"{{"models": [{}]}}"#, entries.join(", "))
+    }
+    /// How deep (z) the custom box under `model`'s part `name` is.
+    fn depth(model: &ModelPart, name: &str) -> f32 {
+        let part = model.child(name).unwrap();
+        let zs = part
+            .children
+            .iter()
+            .flat_map(|(_, c)| c.polygons.iter().flatten().map(|v| v[2]));
+        let (lo, hi) = zs.fold((f32::MAX, f32::MIN), |(lo, hi), z| (lo.min(z), hi.max(z)));
+        hi - lo
+    }
+    /// Whether `model`'s part `name` was replaced by one custom box: its own face gone, and one
+    /// child of a box's six faces.
+    fn replaced(model: &ModelPart, name: &str) -> bool {
+        let part = model.child(name).unwrap();
+        match part.children.as_slice() {
+            [(_, only)] => part.polygons.is_empty() && only.polygons.len() == 6,
+            _ => false,
+        }
+    }
+
+    #[test]
+    fn every_optifine_part_name_lands_on_its_vanilla_part() {
+        // File, OptiFine's part, the model it reshapes, vanilla's part there.
+        let cases = [
+            ("chest", "base", "chest", "bottom"),
+            ("chest", "lid", "chest", "lid"),
+            ("chest", "knob", "chest", "lock"),
+            ("chest_left", "base", "double_chest_left", "bottom"),
+            ("chest_left", "lid", "double_chest_left", "lid"),
+            ("chest_left", "knob", "double_chest_left", "lock"),
+            ("chest_right", "base", "double_chest_right", "bottom"),
+            ("chest_right", "lid", "double_chest_right", "lid"),
+            ("chest_right", "knob", "double_chest_right", "lock"),
+            ("trapped_chest", "base", "trapped_chest", "bottom"),
+            ("trapped_chest", "knob", "trapped_chest", "lock"),
+            ("trapped_chest_left", "base", "trapped_chest_left", "bottom"),
+            ("trapped_chest_left", "knob", "trapped_chest_left", "lock"),
+            (
+                "trapped_chest_right",
+                "base",
+                "trapped_chest_right",
+                "bottom",
+            ),
+            ("trapped_chest_right", "knob", "trapped_chest_right", "lock"),
+            ("ender_chest", "base", "ender_chest", "bottom"),
+            ("ender_chest", "knob", "ender_chest", "lock"),
+            ("shulker_box", "base", "shulker_box", "base"),
+            ("shulker_box", "lid", "shulker_box", "lid"),
+            ("banner", "stand", "standing_banner", "pole"),
+            ("banner", "top", "standing_banner", "bar"),
+            ("banner", "top", "wall_banner", "bar"),
+            ("banner", "slate", "standing_banner_flag", "flag"),
+            ("banner", "slate", "wall_banner_flag", "flag"),
+            ("head_skeleton", "head", "skeleton_skull", "head"),
+            (
+                "head_wither_skeleton",
+                "head",
+                "wither_skeleton_skull",
+                "head",
+            ),
+            ("head_zombie", "head", "zombie_head", "head"),
+            ("head_creeper", "head", "creeper_head", "head"),
+            ("head_dragon", "head", "dragon_skull", "head"),
+            ("head_dragon", "jaw", "dragon_skull", "jaw"),
+            ("head_piglin", "head", "piglin_head", "head"),
+            ("head_piglin", "left_ear", "piglin_head", "left_ear"),
+            ("head_piglin", "right_ear", "piglin_head", "right_ear"),
+            ("head_player", "head", "player_head", "head"),
+            ("bell", "body", "bell", "bell_body"),
+            ("bell", "base", "bell", "bell_base"),
+            ("enchanting_book", "cover_right", "book", "right_lid"),
+            ("enchanting_book", "cover_left", "book", "left_lid"),
+            ("enchanting_book", "pages_right", "book", "right_pages"),
+            ("enchanting_book", "pages_left", "book", "left_pages"),
+            (
+                "enchanting_book",
+                "flipping_page_right",
+                "book",
+                "flip_page1",
+            ),
+            (
+                "enchanting_book",
+                "flipping_page_left",
+                "book",
+                "flip_page2",
+            ),
+            ("enchanting_book", "book_spine", "book", "seam"),
+            ("lectern_book", "cover_right", "lectern_book", "right_lid"),
+            ("lectern_book", "pages_left", "lectern_book", "left_pages"),
+            (
+                "lectern_book",
+                "flipping_page_right",
+                "lectern_book",
+                "flip_page1",
+            ),
+            ("lectern_book", "book_spine", "lectern_book", "seam"),
+            ("conduit", "base", "conduit_shell", "shell"),
+            ("conduit", "cage", "conduit_cage", "shell"),
+            ("conduit", "wind", "conduit_wind", "wind"),
+            ("conduit", "eye", "conduit_eye", "eye"),
+            ("decorated_pot", "neck", "decorated_pot_base", "neck"),
+            ("decorated_pot", "top", "decorated_pot_base", "top"),
+            ("decorated_pot", "bottom", "decorated_pot_base", "bottom"),
+            ("decorated_pot", "front", "decorated_pot_sides", "front"),
+            ("decorated_pot", "back", "decorated_pot_sides", "back"),
+            ("decorated_pot", "left", "decorated_pot_sides", "left"),
+            ("decorated_pot", "right", "decorated_pot_sides", "right"),
+        ];
+        // One file per name with each of its parts, and a stub of each model holding its parts
+        // (chest models all of theirs, so a misplaced entry shows).
+        let mut files: BTreeMap<&str, BTreeSet<&str>> = BTreeMap::new();
+        let mut trees: BTreeMap<&str, BTreeSet<&str>> = BTreeMap::new();
+        for (file, part, key, vanilla) in cases {
+            files.entry(file).or_default().insert(part);
+            trees.entry(key).or_default().insert(vanilla);
+        }
+        for key in ["chest", "double_chest_left", "double_chest_right"] {
+            trees
+                .entry(key)
+                .or_default()
+                .extend(["bottom", "lid", "lock"]);
+        }
+        let files_by_name = files.clone();
+        let files: Vec<_> = files
+            .iter()
+            .map(|(file, parts)| {
+                let parts: Vec<_> = parts.iter().copied().collect();
+                (format!("optifine/cem/{file}.jem"), jem_sized(&parts))
+            })
+            .collect();
+        let files: Vec<_> = files.iter().map(|(p, t)| (p.as_str(), t.clone())).collect();
+        let root = pack("parts", &files);
+        let vanilla: HashMap<&'static str, ModelPart> = trees
+            .iter()
+            .map(|(key, parts)| {
+                let parts = parts.iter().map(|p| (*p, plane(vec![]))).collect();
+                (*key, plane(parts))
+            })
+            .collect();
+        let result = reshape_all(&root, &vanilla);
+        fs::remove_dir_all(&root).unwrap();
+        let ((models, _), unused) = result.unwrap();
+        for (file, part, key, vanilla) in cases {
+            assert!(
+                replaced(&models[key], vanilla),
+                "{file}.jem {part}: {key} {vanilla}"
+            );
+            // The box is this entry's own: swapped names (left and right, body and base) show.
+            let own = files_by_name[file].iter().position(|p| *p == part).unwrap() + 1;
+            assert_eq!(
+                depth(&models[key], vanilla),
+                own as f32,
+                "{file}.jem {part}: {key} {vanilla}"
+            );
+        }
+        assert_eq!(unused, Vec::new());
+    }
+
+    #[test]
+    fn a_chest_jem_reshapes_the_chest_alone_and_warns_of_entries_without_a_part() {
+        let root = pack(
+            "chest",
+            &[(
+                "optifine/cem/chest.jem",
+                format!(
+                    r#"{{"texture": "textures/entity/chest/fancy.png", "models": [
+                        {{"part": "lid", {BOX}}},
+                        {{"part": "knob", "attach": true, "scale": 2, {BOX}}},
+                        {{"part": "bottom", {BOX}}},
+                        {{"part": "tail", {BOX}}}]}}"#
+                ),
+            )],
+        );
+        let vanilla: HashMap<_, _> = [("chest", chest()), ("double_chest_left", chest())].into();
+        let result = reshape_all(&root, &vanilla);
+        fs::remove_dir_all(&root).unwrap();
+        let ((models, textures), unused) = result.unwrap();
+        let chest = &models["chest"];
+        // Replaced: the lid's own face goes and the custom box (6 faces) joins it.
+        assert!(replaced(chest, "lid"));
+        // `bottom` is no OptiFine name but vanilla's own: it reaches the part as well.
+        assert!(replaced(chest, "bottom"));
+        // Attached: the lock keeps its face beside the scaled box.
+        let lock = chest.child("lock").unwrap();
+        assert_eq!((lock.polygons.len(), lock.children.len()), (1, 1));
+        assert_eq!(lock.children[0].1.pose[6..], [2.0, 2.0, 2.0]);
+        // `tail` names no chest part: the one warning.
+        assert_eq!(
+            unused,
+            [(
+                "assets/minecraft/optifine/cem/chest.jem".to_owned(),
+                "tail".to_owned()
+            )]
+        );
+        // The double chest has no file, nor do trapped and ender chests: vanilla's own, and
+        // only the chest takes the texture.
+        for key in ["double_chest_left", "trapped_chest", "ender_chest"] {
+            let lid = models[key].child("lid").unwrap();
+            assert_eq!((lid.polygons.len(), lid.children.len()), (1, 0), "{key}");
+        }
+        assert_eq!(
+            textures,
+            HashMap::from([("chest", "entity/chest/fancy".to_owned())])
+        );
+    }
+
+    #[test]
+    fn banners_split_one_file_and_books_fall_back() {
+        let root = pack(
+            "banner",
+            &[
+                ("optifine/cem/banner.jem", jem(&["stand", "top", "slate"])),
+                ("emf/cem/enchanting_book.jem", jem(&["cover_left"])),
+            ],
+        );
+        let banner = plane(vec![("pole", plane(vec![])), ("bar", plane(vec![]))]);
+        let wall = plane(vec![("bar", plane(vec![]))]);
+        let flag = plane(vec![("flag", plane(vec![]))]);
+        let book = plane(vec![("left_lid", plane(vec![]))]);
+        let vanilla: HashMap<_, _> = [
+            ("standing_banner", banner),
+            ("wall_banner", wall),
+            ("wall_banner_flag", flag),
+            ("book", book),
+        ]
+        .into();
+        let result = reshape_all(&root, &vanilla);
+        fs::remove_dir_all(&root).unwrap();
+        let ((models, textures), unused) = result.unwrap();
+        assert!(replaced(&models["standing_banner"], "pole"));
+        assert!(replaced(&models["standing_banner"], "bar"));
+        assert!(replaced(&models["wall_banner"], "bar"));
+        assert!(replaced(&models["wall_banner_flag"], "flag"));
+        assert!(replaced(&models["book"], "left_lid"));
+        // The lectern's book has no file of its own nor `book.jem`: vanilla's.
+        let lectern = models["lectern_book"].child("left_lid").unwrap();
+        assert_eq!((lectern.polygons.len(), lectern.children.len()), (1, 0));
+        assert!(textures.is_empty());
+        // Each entry found its part in one of the models: no warning.
+        assert_eq!(unused, Vec::new());
+    }
+
+    #[test]
+    fn book_jem_reshapes_the_lectern_book_without_its_own_file() {
+        let root = pack("book", &[("optifine/cem/book.jem", jem(&["cover_left"]))]);
+        let vanilla: HashMap<_, _> = [("book", plane(vec![("left_lid", plane(vec![]))]))].into();
+        let result = reshape(&root, &vanilla);
+        fs::remove_dir_all(&root).unwrap();
+        let (models, _) = result.unwrap();
+        assert!(replaced(&models["book"], "left_lid"));
+        assert!(replaced(&models["lectern_book"], "left_lid"));
+    }
+
+    #[test]
+    fn a_shared_file_paints_only_the_models_it_reshapes() {
+        // The conduit's file reshapes its eye alone: the shell, cage and wind keep their
+        // vanilla geometry and so their own textures.
+        let file = format!(
+            r#"{{"texture": "textures/entity/conduit/custom.png", "models": [{{"part": "eye", {BOX}}}]}}"#
+        );
+        let root = pack("conduit", &[("optifine/cem/conduit.jem", file)]);
+        let vanilla: HashMap<_, _> = [
+            "conduit_shell",
+            "conduit_cage",
+            "conduit_wind",
+            "conduit_eye",
+        ]
+        .map(|key| {
+            let part = if key == "conduit_eye" { "eye" } else { "shell" };
+            (key, plane(vec![(part, plane(vec![]))]))
+        })
+        .into();
+        let result = reshape(&root, &vanilla);
+        fs::remove_dir_all(&root).unwrap();
+        let (models, textures) = result.unwrap();
+        assert!(replaced(&models["conduit_eye"], "eye"));
+        let painted: BTreeSet<_> = textures.keys().copied().collect();
+        assert_eq!(painted, BTreeSet::from(["conduit_eye"]));
+        assert_eq!(textures["conduit_eye"], "entity/conduit/custom");
+    }
+}

crates/horizon-client-render/src/block_entity_render.rs

@@ -20,7 +20,12 @@ use horizon_world::{
     registry::{BlockRegistry, BlockStateId},
 };
 use serde_json::Value;
-use std::{collections::HashMap, f32::consts::PI, path::Path, sync::Mutex};
+use std::{
+    collections::HashMap,
+    f32::consts::PI,
+    path::Path,
+    sync::{Arc, Mutex, PoisonError, RwLock},
+};
 
 /// One baked `ModelPart`: initial pose, textured polygons (pixel units,
 /// normalized UVs) and named children.
@@ -802,16 +807,102 @@ pub struct Scene<'a> {
 /// Empty by default (a dedicated server): no state has a block entity model.
 #[derive(Default)]
 pub struct BlockEntityRenderer {
-    models: HashMap<&'static str, ModelPart>,
+    vanilla: Arc<BlockEntityShapes>,
+    /// What draws: `vanilla`, or the packs' custom entity models over it.
+    shapes: RwLock<Arc<BlockEntityShapes>>,
     kinds: Vec<Kind>,
-    // Closed chest geometry: dimension lighting, chest part, horizontal facing.
-    closed_chests: [[[Vec<Vertex>; 4]; 3]; 2],
     /// Item id to its `PROVIDES_POTTERY_PATTERN` side texture (`Sheets.DECORATED_POT_MAPPER`).
     pot_patterns: HashMap<String, String>,
     /// `Block.shouldRenderFace` for End gateway faces (its occlusion pair cache needs a lock).
     visibility: Option<Mutex<FaceVisibility>>,
     sign_texts: Mutex<SignTexts>,
 }
+/// The block-entity models and what is baked from them: vanilla's, or the packs' custom entity
+/// models over them ([`crate::block_entity_cem`]).
+#[derive(Default)]
+pub struct BlockEntityShapes {
+    models: HashMap<&'static str, ModelPart>,
+    /// Closed chest geometry by chest model: dimension lighting, horizontal facing.
+    closed_chests: HashMap<&'static str, [[Vec<Vertex>; 4]; 2]>,
+    /// A `.jem`'s texture (atlas name) by model, drawn instead of vanilla's.
+    textures: HashMap<&'static str, String>,
+}
+/// The chest models, each baked with its lid closed.
+const CHEST_MODELS: [&str; 7] = [
+    "chest",
+    "double_chest_left",
+    "double_chest_right",
+    "trapped_chest",
+    "trapped_chest_left",
+    "trapped_chest_right",
+    "ender_chest",
+];
+impl BlockEntityShapes {
+    fn new(
+        models: HashMap<&'static str, ModelPart>,
+        textures: HashMap<&'static str, String>,
+    ) -> Self {
+        let closed_chests = CHEST_MODELS
+            .iter()
+            .filter_map(|key| Some((*key, closed_chest(models.get(key)?))))
+            .collect();
+        Self {
+            models,
+            closed_chests,
+            textures,
+        }
+    }
+    /// The texture model `key` draws with: its `.jem`'s when the atlas has it, else `vanilla`.
+    fn texture<'a>(
+        &'a self,
+        key: &str,
+        vanilla: &'a str,
+        sprites: &HashMap<String, Rect>,
+    ) -> &'a str {
+        match self.textures.get(key) {
+            Some(texture) if sprites.contains_key(texture) => texture,
+            _ => vanilla,
+        }
+    }
+}
+/// A chest model with its lid closed, for each dimension lighting and horizontal facing, its UVs
+/// over the whole texture.
+fn closed_chest(model: &ModelPart) -> [[Vec<Vertex>; 4]; 2] {
+    [false, true].map(|nether| {
+        [0.0f32, 90.0, 180.0, 270.0].map(|y_rot| {
+            let mut vertices = Vec::new();
+            draw_part(
+                model,
+                "root",
+                around(
+                    Mat4::from_rotation_y((-y_rot).to_radians()),
+                    Vec3::new(0.5, 0.0, 0.5),
+                ),
+                &|name, p| {
+                    if name == "lid" || name == "lock" {
+                        p[3] = crate::block_entity_anim::chest_lid_x_rot(0.0);
+                    }
+                },
+                Paint {
+                    sprite: Rect {
+                        u0: 0.0,
+                        v0: 0.0,
+                        u1: 1.0,
+                        v1: 1.0,
+                        w: 16,
+                        h: 16,
+                    },
+                    tint: 0xFFFFFF,
+                    light: 0,
+                    lights: diffuse_lights(nether),
+                    glow: None,
+                },
+                &mut vertices,
+            );
+            vertices
+        })
+    })
+}
 /// Laid-out sign text by position. `AbstractSignRenderer` lays the text out
 /// again each frame, glyph by glyph; its vertices only change with what is
 /// in the key, so they are kept relative to the block and moved to the camera.
@@ -894,6 +985,8 @@ impl BlockEntityRenderer {
             .collect();
         let mut renderer = Self::new(models, registry);
         renderer.visibility = Some(Mutex::new(visibility));
+        // The packs' custom entity models (`.jem` files), before anything draws.
+        renderer.set_shapes(renderer.shapes_for(root));
         // Sherd items: provides_pottery_pattern -> decorated_pot_pattern asset id.
         let items = match horizon_world::item_defaults::read(root) {
             Ok(items) => items,
@@ -920,44 +1013,7 @@ impl BlockEntityRenderer {
         Ok(renderer)
     }
     fn new(models: HashMap<&'static str, ModelPart>, registry: &BlockRegistry) -> Self {
-        let closed_chests = [false, true].map(|nether| {
-            ["chest", "double_chest_left", "double_chest_right"].map(|name| {
-                [0.0f32, 90.0, 180.0, 270.0].map(|y_rot| {
-                    let mut vertices = Vec::new();
-                    if let Some(model) = models.get(name) {
-                        draw_part(
-                            model,
-                            "root",
-                            around(
-                                Mat4::from_rotation_y((-y_rot).to_radians()),
-                                Vec3::new(0.5, 0.0, 0.5),
-                            ),
-                            &|name, p| {
-                                if name == "lid" || name == "lock" {
-                                    p[3] = crate::block_entity_anim::chest_lid_x_rot(0.0);
-                                }
-                            },
-                            Paint {
-                                sprite: Rect {
-                                    u0: 0.0,
-                                    v0: 0.0,
-                                    u1: 1.0,
-                                    v1: 1.0,
-                                    w: 16,
-                                    h: 16,
-                                },
-                                tint: 0xFFFFFF,
-                                light: 0,
-                                lights: diffuse_lights(nether),
-                                glow: None,
-                            },
-                            &mut vertices,
-                        );
-                    }
-                    vertices
-                })
-            })
-        });
+        let vanilla = Arc::new(BlockEntityShapes::new(models, HashMap::new()));
         let kinds = (0..registry.len() as u32)
             .map(|id| {
                 registry.state(BlockStateId(id)).map_or(Kind::None, |s| {
@@ -970,14 +1026,31 @@ impl BlockEntityRenderer {
             })
             .collect();
         Self {
-            models,
+            shapes: RwLock::new(vanilla.clone()),
+            vanilla,
             kinds,
-            closed_chests,
             pot_patterns: HashMap::new(),
             visibility: None,
             sign_texts: Mutex::default(),
         }
     }
+    /// The models the packs under `root` give, their `.jem` files over vanilla's, for
+    /// [`Self::set_shapes`] (a pack reload): vanilla's own, shared, without any.
+    pub fn shapes_for(&self, root: &Path) -> Arc<BlockEntityShapes> {
+        match crate::block_entity_cem::reshape(root, &self.vanilla.models) {
+            Some((models, textures)) => Arc::new(BlockEntityShapes::new(models, textures)),
+            None => self.vanilla.clone(),
+        }
+    }
+    pub fn set_shapes(&self, shapes: Arc<BlockEntityShapes>) {
+        *self.shapes.write().unwrap_or_else(PoisonError::into_inner) = shapes;
+    }
+    fn shapes(&self) -> Arc<BlockEntityShapes> {
+        self.shapes
+            .read()
+            .unwrap_or_else(PoisonError::into_inner)
+            .clone()
+    }
     fn kind(&self, state: u32) -> &Kind {
         self.kinds.get(state as usize).unwrap_or(&Kind::None)
     }
@@ -1271,6 +1344,7 @@ impl BlockEntityRenderer {
         world_chests: bool,
         out: &mut Vec<Vertex>,
     ) {
+        let shapes = self.shapes();
         let sprite = |name: &str| scene.sprites.get(name).copied();
         let paint = |name: &str, tint: u32, packed: u8| {
             let rect = if crumbling {
@@ -1363,12 +1437,34 @@ impl BlockEntityRenderer {
                 } else {
                     *texture
                 };
-                let model = match part {
-                    ChestPart::Single => "chest",
-                    ChestPart::Left => "double_chest_left",
-                    ChestPart::Right => "double_chest_right",
+                // Trapped and ender chests have models of their own when a `.jem` reshapes
+                // them; copper chests have no CEM name and draw vanilla's chest.
+                let shapes: &BlockEntityShapes =
+                    if matches!(block.as_str(), "chest" | "trapped_chest" | "ender_chest") {
+                        &shapes
+                    } else {
+                        &self.vanilla
+                    };
+                let (own, chest) = match (block.as_str(), part) {
+                    ("trapped_chest", ChestPart::Single) => ("trapped_chest", "chest"),
+                    ("trapped_chest", ChestPart::Left) => {
+                        ("trapped_chest_left", "double_chest_left")
+                    }
+                    ("trapped_chest", ChestPart::Right) => {
+                        ("trapped_chest_right", "double_chest_right")
+                    }
+                    ("ender_chest", _) => ("ender_chest", "chest"),
+                    (_, ChestPart::Single) => ("chest", "chest"),
+                    (_, ChestPart::Left) => ("double_chest_left", "double_chest_left"),
+                    (_, ChestPart::Right) => ("double_chest_right", "double_chest_right"),
                 };
-                let Some(model) = self.models.get(model) else {
+                let key = if shapes.models.contains_key(own) {
+                    own
+                } else {
+                    chest
+                };
+                let texture = shapes.texture(key, texture, scene.sprites);
+                let Some(model) = shapes.models.get(key) else {
                     return;
                 };
                 let (open, other) = self.chest_openness(
@@ -1384,9 +1480,11 @@ impl BlockEntityRenderer {
                     packed = (packed >> 4).max(l >> 4) << 4 | (packed & 15).max(l & 15);
                 }
                 if world_chests && open == 0.0 {
-                    if let Some(paint) = paint(texture, 0xFFFFFF, packed) {
-                        let vertices = &self.closed_chests[usize::from(scene.nether)]
-                            [*part as usize][*y_rot as usize / 90];
+                    if let (Some(paint), Some(closed)) = (
+                        paint(texture, 0xFFFFFF, packed),
+                        shapes.closed_chests.get(key),
+                    ) {
+                        let vertices = &closed[usize::from(scene.nether)][*y_rot as usize / 90];
                         let origin = base.w_axis.truncate();
                         let passes = std::iter::once((paint.sprite, paint.light))
                             .chain(paint.glow.map(|g| (g, FULL_BRIGHT)));
@@ -1421,8 +1519,12 @@ impl BlockEntityRenderer {
             }
             Kind::Shulker { texture, facing } => {
                 let (Some(model), Some(paint)) = (
-                    self.models.get("shulker_box"),
-                    paint(texture, 0xFFFFFF, packed),
+                    shapes.models.get("shulker_box"),
+                    paint(
+                        shapes.texture("shulker_box", texture, scene.sprites),
+                        0xFFFFFF,
+                        packed,
+                    ),
                 ) else {
                     return;
                 };
@@ -1446,12 +1548,13 @@ impl BlockEntityRenderer {
                 draw_part(model, "root", m, &lid, paint, out);
             }
             Kind::Banner { color, wall, angle } => {
-                let (main, flag) = if *wall {
+                let (main_key, flag_key) = if *wall {
                     ("wall_banner", "wall_banner_flag")
                 } else {
                     ("standing_banner", "standing_banner_flag")
                 };
-                let (Some(main), Some(flag)) = (self.models.get(main), self.models.get(flag))
+                let (Some(main), Some(flag)) =
+                    (shapes.models.get(main_key), shapes.models.get(flag_key))
                 else {
                     return;
                 };
@@ -1472,8 +1575,13 @@ impl BlockEntityRenderer {
                         p[3] = (-0.0125 + 0.01 * (2.0 * PI * phase).mcos()) * PI;
                     }
                 };
-                if let Some(paint) = paint("entity/banner/banner_base", 0xFFFFFF, packed) {
+                let banner_base = "entity/banner/banner_base";
+                let main_texture = shapes.texture(main_key, banner_base, scene.sprites);
+                if let Some(paint) = paint(main_texture, 0xFFFFFF, packed) {
                     draw_part(main, "root", m, &none, paint, out);
+                }
+                let flag_texture = shapes.texture(flag_key, banner_base, scene.sprites);
+                if let Some(paint) = paint(flag_texture, 0xFFFFFF, packed) {
                     draw_part(flag, "root", m, &wave, paint, out);
                 }
                 // Pattern passes must not multiply the crumbling decal.
@@ -1515,9 +1623,12 @@ impl BlockEntityRenderer {
                     None
                 };
                 let has_profile = skin.is_some();
-                let texture = skin.as_deref().unwrap_or(texture);
+                // A `.jem` texture stands in for the default skin, not a profile's.
+                let texture = skin
+                    .as_deref()
+                    .unwrap_or_else(|| shapes.texture(model, texture, scene.sprites));
                 let (Some(model), Some(paint)) =
-                    (self.models.get(model), paint(texture, 0xFFFFFF, packed))
+                    (shapes.models.get(model), paint(texture, 0xFFFFFF, packed))
                 else {
                     return;
                 };
@@ -1559,8 +1670,12 @@ impl BlockEntityRenderer {
             }
             Kind::Bell => {
                 let (Some(model), Some(paint)) = (
-                    self.models.get("bell"),
-                    paint("entity/bell/bell_body", 0xFFFFFF, packed),
+                    shapes.models.get("bell"),
+                    paint(
+                        shapes.texture("bell", "entity/bell/bell_body", scene.sprites),
+                        0xFFFFFF,
+                        packed,
+                    ),
                 ) else {
                     return;
                 };
@@ -1588,8 +1703,8 @@ impl BlockEntityRenderer {
             }
             Kind::DecoratedPot { y_rot } => {
                 let (Some(base_model), Some(sides)) = (
-                    self.models.get("decorated_pot_base"),
-                    self.models.get("decorated_pot_sides"),
+                    shapes.models.get("decorated_pot_base"),
+                    shapes.models.get("decorated_pot_sides"),
                 ) else {
                     return;
                 };
@@ -1617,17 +1732,20 @@ impl BlockEntityRenderer {
                     }
                 }
                 let first = out.len();
-                if let Some(paint) =
-                    paint("entity/decorated_pot/decorated_pot_base", 0xFFFFFF, packed)
-                {
+                let pot_base = "entity/decorated_pot/decorated_pot_base";
+                let pot_base = shapes.texture("decorated_pot_base", pot_base, scene.sprites);
+                if let Some(paint) = paint(pot_base, 0xFFFFFF, packed) {
                     draw_part(base_model, "root", m, &none, paint, out);
                 }
-                // PotDecorations (back, left, right, front); items without a pattern use the blank side.
+                // PotDecorations (back, left, right, front); items without a pattern use the blank
+                // side (a `.jem`'s texture, if any).
+                let blank = "entity/decorated_pot/decorated_pot_side";
+                let blank = shapes.texture("decorated_pot_sides", blank, scene.sprites);
                 for (side, item) in ["back", "left", "right", "front"].iter().zip(&a.sherds) {
                     let texture = item
                         .as_ref()
                         .and_then(|i| self.pot_patterns.get(i))
-                        .map_or("entity/decorated_pot/decorated_pot_side", String::as_str);
+                        .map_or(blank, String::as_str);
                     if let (Some(part), Some(paint)) =
                         (sides.child(side), paint(texture, 0xFFFFFF, packed))
                     {
@@ -1677,11 +1795,14 @@ impl BlockEntityRenderer {
                 let (ticks, active, hunting, raw_rotation) = (scene.anim)(pos).conduit;
                 // ConduitRenderer.extractRenderState.
                 let rotation = (raw_rotation + if active { scene.partial } else { 0.0 }) * -0.0375;
-                let tex = |name: &str| paint(name, 0xFFFFFF, packed);
+                let tex = |key: &str, name: &str| {
+                    paint(shapes.texture(key, name, scene.sprites), 0xFFFFFF, packed)
+                };
                 if !active {
-                    let (Some(model), Some(paint)) =
-                        (self.models.get("conduit_shell"), tex("entity/conduit/base"))
-                    else {
+                    let (Some(model), Some(paint)) = (
+                        shapes.models.get("conduit_shell"),
+                        tex("conduit_shell", "entity/conduit/base"),
+                    ) else {
                         return;
                     };
                     let m = base
@@ -1696,9 +1817,10 @@ impl BlockEntityRenderer {
                 let hh = (anim_time * 0.1).msin() / 2.0 + 0.5;
                 let hh = hh * hh + hh;
                 let lift = Vec3::new(0.5, 0.3 + hh * 0.2, 0.5);
-                if let (Some(model), Some(paint)) =
-                    (self.models.get("conduit_cage"), tex("entity/conduit/cage"))
-                {
+                if let (Some(model), Some(paint)) = (
+                    shapes.models.get("conduit_cage"),
+                    tex("conduit_cage", "entity/conduit/cage"),
+                ) {
                     let axis = Vec3::new(0.5, 1.0, 0.5).normalize();
                     let m = base
                         * Mat4::from_translation(lift)
@@ -1714,7 +1836,9 @@ impl BlockEntityRenderer {
                 } else {
                     "entity/conduit/wind"
                 };
-                if let (Some(model), Some(paint)) = (self.models.get("conduit_wind"), tex(wind)) {
+                if let (Some(model), Some(paint)) =
+                    (shapes.models.get("conduit_wind"), tex("conduit_wind", wind))
+                {
                     let turn = match phase {
                         1 => Mat4::from_rotation_x(PI / 2.0),
                         2 => Mat4::from_rotation_z(PI / 2.0),
@@ -1732,7 +1856,9 @@ impl BlockEntityRenderer {
                 } else {
                     "entity/conduit/closed_eye"
                 };
-                if let (Some(model), Some(paint)) = (self.models.get("conduit_eye"), tex(eye)) {
+                if let (Some(model), Some(paint)) =
+                    (shapes.models.get("conduit_eye"), tex("conduit_eye", eye))
+                {
                     let m = base
                         * Mat4::from_translation(lift)
                         * Mat4::from_scale(Vec3::splat(0.5))
@@ -1743,9 +1869,14 @@ impl BlockEntityRenderer {
                 }
             }
             Kind::EnchantingTable => {
+                let book = "entity/enchantment/enchanting_table_book";
                 let (Some(model), Some(paint)) = (
-                    self.models.get("book"),
-                    paint("entity/enchantment/enchanting_table_book", 0xFFFFFF, packed),
+                    shapes.models.get("book"),
+                    paint(
+                        shapes.texture("book", book, scene.sprites),
+                        0xFFFFFF,
+                        packed,
+                    ),
                 ) else {
                     return;
                 };
@@ -1764,9 +1895,16 @@ impl BlockEntityRenderer {
                 draw_part(model, "root", m, &book_pose(openness, ff1, ff2), paint, out);
             }
             Kind::Lectern { y_rot } => {
+                // Its own `.jem`'s book, else the enchanting table's.
+                let key = if shapes.models.contains_key("lectern_book") {
+                    "lectern_book"
+                } else {
+                    "book"
+                };
+                let book = "entity/enchantment/enchanting_table_book";
                 let (Some(model), Some(paint)) = (
-                    self.models.get("book"),
-                    paint("entity/enchantment/enchanting_table_book", 0xFFFFFF, packed),
+                    shapes.models.get(key),
+                    paint(shapes.texture(key, book, scene.sprites), 0xFFFFFF, packed),
                 ) else {
                     return;
                 };
@@ -1797,7 +1935,7 @@ impl BlockEntityRenderer {
                     _ => "copper_golem",
                 };
                 let (Some(model), Some(paint)) =
-                    (self.models.get(key), paint(texture, 0xFFFFFF, packed))
+                    (shapes.models.get(key), paint(texture, 0xFFFFFF, packed))
                 else {
                     return;
                 };
@@ -2449,7 +2587,8 @@ mod tests {
     #[test]
     fn cached_sign_text_matches_and_follows_changes() {
         let renderer = BlockEntityRenderer {
-            models: HashMap::new(),
+            vanilla: Default::default(),
+            shapes: Default::default(),
             kinds: vec![
                 Kind::Sign {
                     hanging: false,
@@ -2462,7 +2601,6 @@ mod tests {
                     angle: 90.0,
                 },
             ],
-            closed_chests: Default::default(),
             pot_patterns: HashMap::new(),
             visibility: None,
             sign_texts: Mutex::default(),
@@ -2646,4 +2784,131 @@ mod tests {
             "entitySolid culls the pot's back faces"
         );
     }
+
+    #[test]
+    fn a_chest_jem_reshapes_the_closed_chest_and_paints_its_texture() {
+        use crate::block_entity_cem::tests::{BOX, chest, pack};
+        let vanilla = Arc::new(BlockEntityShapes::new(
+            HashMap::from([("chest", chest())]),
+            HashMap::new(),
+        ));
+        let renderer = BlockEntityRenderer {
+            shapes: RwLock::new(vanilla.clone()),
+            vanilla,
+            kinds: Vec::new(),
+            pot_patterns: HashMap::new(),
+            visibility: None,
+            sign_texts: Mutex::default(),
+        };
+        // No block entity's `.jem` (a mob's only): vanilla's shapes, not a copy.
+        let empty = pack("render-none", &[("optifine/cem/zombie.jem", "{}".into())]);
+        assert!(Arc::ptr_eq(&renderer.shapes_for(&empty), &renderer.vanilla));
+        let root = pack(
+            "render-chest",
+            &[(
+                "optifine/cem/chest.jem",
+                format!(
+                    r#"{{"texture": "textures/entity/chest/fancy.png",
+                        "models": [{{"part": "lid", {BOX}}}]}}"#
+                ),
+            )],
+        );
+        renderer.set_shapes(renderer.shapes_for(&root));
+        let _ = std::fs::remove_dir_all(&root);
+        let _ = std::fs::remove_dir_all(&empty);
+        let rect = |u0: f32| Rect {
+            u0,
+            v0: 0.0,
+            u1: u0 + 0.2,
+            v1: 0.2,
+            w: 16,
+            h: 16,
+        };
+        let sprites: HashMap<String, Rect> = [
+            ("entity/chest/normal", rect(0.0)),
+            ("entity/chest/ender", rect(0.2)),
+            ("entity/chest/fancy", rect(0.4)),
+            ("entity/chest/copper", rect(0.6)),
+        ]
+        .map(|(name, r)| (name.to_owned(), r))
+        .into();
+        let world = World::new(BlockStateId(0), 1);
+        let scene = Scene {
+            camera: DVec3::ZERO,
+            orientation: Quat::IDENTITY,
+            anim: &|_| BlockAnim::default(),
+            texts: None,
+            partial: 0.0,
+            game_time: 0,
+            max_y: 320,
+            world: &world,
+            sprites: &sprites,
+            emissive: &Default::default(),
+            nether: false,
+            lid: &|_| 0.0,
+            sign: &|_| None,
+            banner: &|_| Vec::new(),
+            skull: &|_| None,
+            glyph: &|_| (None, 0.0),
+            glyphs: 0,
+        };
+        // A closed single chest of `block` drawn by `renderer`: positions and UVs.
+        let draw = |renderer: &BlockEntityRenderer, block: &str, texture: &'static str| {
+            let kind = Kind::Chest {
+                block: block.into(),
+                texture,
+                part: ChestPart::Single,
+                y_rot: 0.0,
+                double_with: None,
+            };
+            let mut out = Vec::new();
+            renderer.render_one(
+                &scene,
+                [0; 3],
+                &kind,
+                Mat4::IDENTITY,
+                0xF0,
+                diffuse_lights(false),
+                false,
+                true,
+                &mut out,
+            );
+            out.iter().map(|v| (v.pos, v.uv)).collect::<Vec<_>>()
+        };
+        // The chest's three faces become the bottom's, the lock's and the custom lid's six, in
+        // the `.jem`'s texture. Ender and copper chests have no file of their own: vanilla's
+        // three faces in their own textures. (Trapped chests: `block_entity_cem`'s tests; their
+        // texture turns festive in late December.)
+        for (block, texture, u0, faces) in [
+            ("chest", "entity/chest/normal", 0.4, 8),
+            ("ender_chest", "entity/chest/ender", 0.2, 3),
+            ("copper_chest", "entity/chest/copper", 0.6, 3),
+        ] {
+            let out = draw(&renderer, block, texture);
+            assert_eq!(out.len(), faces * 4, "{block}");
+            assert!(
+                out.iter().all(|(_, uv)| (u0..=u0 + 0.2).contains(&uv[0])),
+                "{block}"
+            );
+        }
+        // A copper chest draws exactly what it draws without any pack.
+        let plain = BlockEntityRenderer {
+            shapes: RwLock::new(renderer.vanilla.clone()),
+            vanilla: renderer.vanilla.clone(),
+            kinds: Vec::new(),
+            pot_patterns: HashMap::new(),
+            visibility: None,
+            sign_texts: Mutex::default(),
+        };
+        assert_eq!(
+            draw(&renderer, "copper_chest", "entity/chest/copper"),
+            draw(&plain, "copper_chest", "entity/chest/copper")
+        );
+        // The atlas has no such texture: vanilla's.
+        let shapes = renderer.shapes();
+        assert_eq!(
+            shapes.texture("chest", "entity/chest/normal", &HashMap::new()),
+            "entity/chest/normal"
+        );
+    }
 }

crates/horizon-client-render/src/brewing.rs

@@ -9,7 +9,7 @@ use crate::{
 };
 use horizon_world::loot::PackOverlay;
 use serde_json::Value;
-use std::{collections::HashSet, fs, path::Path};
+use std::{collections::HashSet, path::Path};
 
 pub use horizon_client_core::potions::{
     BASE_POTION_COLOR, Category, EFFECTS, EffectDef, POTIONS, PotionDef, all_effects,
@@ -158,6 +158,28 @@ pub struct Brewing {
     /// Items accepted in the bottle slots (`PotionIngredient.isPotionInput`).
     pub inputs: HashSet<String>,
 }
+/// The files right in `recipe/brewing/`, parsed, by id: taken from the whole
+/// recipe folder's read when another table holds it (the start loads them
+/// together), else read alone. A file that doesn't parse is left out.
+fn brewing_sources(root: &Path) -> Vec<(String, Value)> {
+    let recipe = root.join("data/minecraft/recipe");
+    let (folder, prefix) = match crate::json_folder::held(&recipe) {
+        Some(folder) => (folder, "brewing/"),
+        None => match crate::json_folder::read(&recipe.join("brewing")) {
+            Ok(folder) => (folder, ""),
+            Err(_) => return Vec::new(),
+        },
+    };
+    folder
+        .files
+        .iter()
+        .filter_map(|f| {
+            let name = f.name.strip_prefix(prefix).filter(|n| !n.contains('/'))?;
+            let v = serde_json::from_slice::<Value>(f.bytes().ok()?).ok()?;
+            Some((format!("minecraft:brewing/{name}"), v))
+        })
+        .collect()
+}
 impl Brewing {
     pub fn load(root: &Path, items: &Items, overlay: &PackOverlay) -> Self {
         // NeoForge's load conditions: a file whose don't hold is silently
@@ -172,23 +194,7 @@ impl Brewing {
         let conditions_hold = |v: &Value| {
             horizon_world::conditions::conditions_hold(v, &|id: &str| mods.iter().any(|m| m == id))
         };
-        let mut sources: Vec<(String, Value)> =
-            fs::read_dir(root.join("data/minecraft/recipe/brewing"))
-                .into_iter()
-                .flatten()
-                .flatten()
-                .filter_map(|e| {
-                    let bytes = fs::read(e.path()).ok()?;
-                    let v = serde_json::from_slice::<Value>(&bytes).ok()?;
-                    Some((
-                        format!(
-                            "minecraft:brewing/{}",
-                            e.file_name().to_string_lossy().strip_suffix(".json")?
-                        ),
-                        v,
-                    ))
-                })
-                .collect();
+        let mut sources: Vec<(String, Value)> = brewing_sources(root);
         // The world's packs' brewing recipes over the game's own: the top
         // pack's file for each id replaces it (`SimpleJsonResourceReloadListener`).
         for (id, files) in overlay.kind("recipe") {

crates/horizon-client-render/src/chunk.rs

@@ -644,6 +644,10 @@ impl RolledLoot {
 /// Save data loaded with a chunk that Horizon keeps but does not simulate.
 #[derive(Clone, Debug, Default)]
 pub struct ChunkExtras {
+    /// Server-owned mod data attached to this chunk.
+    pub attachments: horizon_world::attachments::Attachments,
+    /// Attachment maps of the chunk's block entities, on a save snapshot.
+    pub block_entity_attachments: Vec<((i32, i32, i32), horizon_world::attachments::Attachments)>,
     /// Chunk root keys written back as loaded (structures, PostProcessing,
     /// InhabitedTime, blending data, ...).
     pub root: Compound,

crates/horizon-client-render/src/cit.rs

@@ -4,6 +4,7 @@
 
 pub use horizon_optifine::cit::{Hand, Kind, Rule};
 
+use crate::cit_glint::{Global, StackGlint};
 use horizon_client_core::component::name_text;
 use horizon_client_core::scoreboard::comp_text;
 use horizon_items::item_data::{canon_tag, encode_components};
@@ -16,7 +17,7 @@ use std::collections::HashMap;
 use std::fs;
 use std::hash::{DefaultHasher, Hash, Hasher};
 use std::path::Path;
-use std::sync::Mutex;
+use std::sync::{Arc, Mutex};
 
 /// Every rule under the root's `optifine/cit/`, `mcpatcher/cit/` and CIT Resewn's
 /// `citresewn/cit/` folders, the one chosen first when several match first (`Rule::priority`).
@@ -27,13 +28,8 @@ pub fn load_rules(root: &Path) -> Vec<Rule> {
         .into_iter()
         .filter(|path| !path.ends_with("/cit.properties"))
         .filter_map(|path| {
-            // Java reads `.properties` as Latin-1: a pack saved that way still loads.
-            let bytes = fs::read(root.join(&path)).ok()?;
-            let text = String::from_utf8(bytes)
-                .unwrap_or_else(|e| e.into_bytes().iter().map(|&b| char::from(b)).collect());
-            let rule = Rule::parse(&path, &Properties::parse_equals_first(&text), |p| {
-                root.join(p).is_file()
-            });
+            let props = read_properties(&root.join(&path))?;
+            let rule = Rule::parse(&path, &props, |p| root.join(p).is_file());
             if rule.is_none() {
                 log::warn!("custom item textures: {path} is not a rule Horizon can read");
             }
@@ -44,10 +40,22 @@ pub fn load_rules(root: &Path) -> Vec<Rule> {
     rules
 }
 
+/// A `.properties` file as CIT Resewn reads them (`Properties::parse_equals_first`): UTF-8,
+/// else Latin-1 as Java reads them, so a pack saved that way still loads. `None` when it can't
+/// be read.
+pub fn read_properties(path: &Path) -> Option<Properties> {
+    let bytes = fs::read(path).ok()?;
+    let text = String::from_utf8(bytes)
+        .unwrap_or_else(|e| e.into_bytes().iter().map(|&b| char::from(b)).collect());
+    Some(Properties::parse_equals_first(&text))
+}
+
 /// The rules with an index by item and a cache of what each stack matched.
 #[derive(Debug, Default)]
 pub struct CitRules {
     pub rules: Vec<Rule>,
+    /// The pack's `cit.properties`.
+    pub global: Global,
     /// Per kind (`Kind as usize`), the rules naming each item, in priority order.
     by_item: [HashMap<String, Vec<u32>>; 4],
     /// Enchantment rules without `items`, in priority order.
@@ -56,6 +64,7 @@ pub struct CitRules {
     literals: Vec<Vec<Prepared>>,
     selected: Mutex<HashMap<u64, Option<u32>>>,
     enchanted: Mutex<HashMap<u64, Vec<u32>>>,
+    glints: Mutex<HashMap<u64, Arc<StackGlint>>>,
 }
 
 #[derive(Debug, Default)]
@@ -70,7 +79,10 @@ const CACHE_LIMIT: usize = 4096;
 impl CitRules {
     /// The enabled packs' rules under the overlay resource root.
     pub fn load(root: &Path) -> Self {
-        Self::new(load_rules(root))
+        Self {
+            global: crate::cit_glint::load_global(root),
+            ..Self::new(load_rules(root))
+        }
     }
 
     /// `rules` in priority order, the winner first.
@@ -106,6 +118,19 @@ impl CitRules {
         self.rules.is_empty()
     }
 
+    /// Leave out the Enchantment rules `keep` refuses (those without a drawable texture): they
+    /// match no stack, so vanilla's glint and the other rules of their layer stay.
+    pub fn keep_glints(&mut self, keep: impl Fn(usize) -> bool) {
+        self.any_item.retain(|&i| keep(i as usize));
+        let named = &mut self.by_item[Kind::Enchantment as usize];
+        for list in named.values_mut() {
+            list.retain(|&i| keep(i as usize));
+        }
+        named.retain(|_, list| !list.is_empty());
+        lock(&self.enchanted).clear();
+        lock(&self.glints).clear();
+    }
+
     /// The winning rule of `kind` (Item, Armor or Elytra) for this stack, as an index into `rules`.
     pub fn select(
         &self,
@@ -123,13 +148,14 @@ impl CitRules {
         let found = candidates
             .iter()
             .copied()
-            .find(|&i| self.matches(i, stack, Some(hand), max_damage, comps.as_ref()));
+            .find(|&i| self.matches(i, stack, hand, max_damage, comps.as_ref()));
         remember(&self.selected, key, found);
         found.map(|i| i as usize)
     }
 
-    /// Every matching Enchantment rule, in priority order (layers are the glint PR's business).
-    pub fn enchantments(&self, stack: &ItemStack, max_damage: u32) -> Vec<usize> {
+    /// Every matching Enchantment rule for the stack drawn in `hand` (`Hand::Main` for one in a
+    /// GUI), in priority order.
+    pub fn enchantments(&self, stack: &ItemStack, hand: Hand, max_damage: u32) -> Vec<usize> {
         let named = self.by_item[Kind::Enchantment as usize]
             .get(&*stack.item)
             .map_or(&[][..], Vec::as_slice);
@@ -138,7 +164,7 @@ impl CitRules {
         }
         let comps = encode_components(stack);
         let key = cache_key(
-            (1, Kind::Enchantment, Hand::Any),
+            (1, Kind::Enchantment, hand),
             stack,
             max_damage,
             comps.as_ref(),
@@ -147,24 +173,62 @@ impl CitRules {
         let found = hit.unwrap_or_else(|| {
             let mut all: Vec<u32> = named.iter().chain(&self.any_item).copied().collect();
             all.sort_unstable();
-            all.retain(|&i| self.matches(i, stack, None, max_damage, comps.as_ref()));
+            all.retain(|&i| self.matches(i, stack, hand, max_damage, comps.as_ref()));
             remember(&self.enchanted, key, all.clone());
             all
         });
         found.into_iter().map(|i| i as usize).collect()
     }
 
-    /// Whether rule `i` matches; `hand` None skips the hand test (enchantment glints).
+    /// The glint layers this stack draws in `hand` (`Hand::Main` in a GUI) and whether
+    /// vanilla's still does (`StackGlint`), worked out once per stack and hand; `None` when the
+    /// pack changes no glint. `foil` is whether the stack draws a glint at all
+    /// (`ItemStack::has_foil`): one that doesn't gets no layers.
+    pub fn glint(
+        &self,
+        stack: &ItemStack,
+        hand: Hand,
+        max_damage: u32,
+        foil: bool,
+    ) -> Option<Arc<StackGlint>> {
+        let no_rules =
+            self.any_item.is_empty() && self.by_item[Kind::Enchantment as usize].is_empty();
+        // Before the cache, which `foil` is not part of.
+        if !foil || (no_rules && self.global.use_glint) {
+            return None;
+        }
+        let comps = encode_components(stack);
+        let key = cache_key(
+            (2, Kind::Enchantment, hand),
+            stack,
+            max_damage,
+            comps.as_ref(),
+        );
+        if let Some(hit) = lock(&self.glints).get(&key) {
+            return Some(hit.clone());
+        }
+        let matched = self.enchantments(stack, hand, max_damage);
+        let glint = Arc::new(StackGlint::new(
+            &self.rules,
+            &matched,
+            stack.crafting_enchantments(),
+            &self.global,
+        ));
+        remember(&self.glints, key, glint.clone());
+        Some(glint)
+    }
+
+    /// Whether rule `i` matches the stack drawn in `hand`.
     fn matches(
         &self,
         i: u32,
         stack: &ItemStack,
-        hand: Option<Hand>,
+        hand: Hand,
         max_damage: u32,
         comps: Option<&Tag>,
     ) -> bool {
         let rule = &self.rules[i as usize];
-        if hand.is_some_and(|h| rule.hand != Hand::Any && rule.hand != h) {
+        if rule.hand != Hand::Any && rule.hand != hand {
             return false;
         }
         let count = i32::try_from(stack.count).unwrap_or(i32::MAX);
@@ -214,7 +278,7 @@ fn remember<V>(cache: &Mutex<HashMap<u64, V>>, key: u64, value: V) {
     cache.insert(key, value);
 }
 
-/// What a cached answer depends on; `query` tells `select` from `enchantments`.
+/// What a cached answer depends on; `query` tells `select`, `enchantments` and `glint` apart.
 fn cache_key(query: (u8, Kind, Hand), stack: &ItemStack, max: u32, comps: Option<&Tag>) -> u64 {
     let mut h = DefaultHasher::new();
     (query.0, query.1 as u8, query.2 as u8, &*stack.item).hash(&mut h);
@@ -646,7 +710,7 @@ mod tests {
         );
         assert_eq!(item(&cit, enchanted("stone", &mixed)), Some("any3"));
         let glints = |stack: ItemStack| -> Vec<&str> {
-            let found = cit.enchantments(&stack, 0).into_iter();
+            let found = cit.enchantments(&stack, Hand::Main, 0).into_iter();
             found.map(|i| stem(&cit, Some(i)).unwrap()).collect()
         };
         let sharp = [("sharpness", 1)];
@@ -659,4 +723,127 @@ mod tests {
         // Glints are never an item's texture.
         assert_eq!(item(&cit, enchanted("diamond_sword", &sharp)), None);
     }
+
+    /// `CitRules::glint` in the main hand, with the stack's own `has_foil` as callers pass it.
+    fn glint(cit: &CitRules, stack: &ItemStack, item_glint: bool) -> Option<Arc<StackGlint>> {
+        cit.glint(stack, Hand::Main, 0, stack.has_foil(item_glint))
+    }
+
+    /// `stack` with its `enchantment_glint_override` set to `on`.
+    fn overridden(mut stack: ItemStack, on: bool) -> ItemStack {
+        let flag = (
+            "minecraft:enchantment_glint_override".to_owned(),
+            Tag::Byte(on.into()),
+        );
+        stack.data_mut().other.push(flag);
+        stack
+    }
+
+    #[test]
+    fn a_stack_glint_reads_the_book_and_the_pack_file() {
+        let mut cit = rules(&[
+            ("sharp", "type=enchantment\nenchantments=sharpness"),
+            (
+                "keep",
+                "type=enchantment\nlayer=1\nuseGlint=true\nenchantments=mending",
+            ),
+        ]);
+        // An enchanted book's glint follows its stored enchantments.
+        let mut book = new("enchanted_book");
+        book.data_mut().stored_enchantments = vec![
+            (Arc::from("minecraft:sharpness"), 3),
+            (Arc::from("minecraft:mending"), 1),
+        ];
+        let book = glint(&cit, &book, true).unwrap();
+        let weights: Vec<_> = book.layers.iter().map(|l| l.weight).collect();
+        assert_eq!(weights, [0.75, 0.25]);
+        assert!(book.vanilla);
+        let plain = glint(&cit, &enchanted("stick", &[("sharpness", 1)]), false).unwrap();
+        assert_eq!(plain.layers.len(), 1);
+        assert!(!plain.vanilla);
+        // No enchantment rules: nothing changes, unless the pack turns vanilla's glint off.
+        let mut bare = rules(&[("stick", "items=stick")]);
+        assert!(glint(&bare, &overridden(new("stick"), true), false).is_none());
+        bare.global.use_glint = false;
+        assert!(
+            !glint(&bare, &overridden(new("stick"), true), false)
+                .unwrap()
+                .vanilla
+        );
+        cit.global.use_glint = false;
+        assert!(
+            glint(&cit, &overridden(new("stick"), true), false)
+                .unwrap()
+                .is_empty()
+        );
+    }
+
+    #[test]
+    fn only_a_stack_with_a_glint_gets_layers() {
+        let cit = rules(&[("any", "type=enchantment")]);
+        assert!(glint(&cit, &new("stick"), false).is_none());
+        // The override turns an enchanted stack's glint off, and an unenchanted one's on.
+        let off = overridden(enchanted("stick", &[("sharpness", 1)]), false);
+        assert!(glint(&cit, &off, false).is_none());
+        let on = glint(&cit, &overridden(new("stick"), true), false).unwrap();
+        let weights: Vec<_> = on.layers.iter().map(|l| l.weight).collect();
+        assert_eq!(
+            weights,
+            [1.0],
+            "nothing to share: the rule at full strength"
+        );
+        // The same stack, asked again without its glint, is not answered from the cache.
+        assert!(
+            cit.glint(&overridden(new("stick"), true), Hand::Main, 0, false)
+                .is_none()
+        );
+    }
+
+    #[test]
+    fn a_rule_left_out_of_the_glints_matches_nothing() {
+        let mut cit = rules(&[
+            ("broken", "type=enchantment\nitems=diamond_sword\nweight=1"),
+            ("shown", "type=enchantment"),
+        ]);
+        let sword = enchanted("diamond_sword", &[("sharpness", 1)]);
+        let layers = |cit: &CitRules| -> Vec<String> {
+            let glint = glint(cit, &sword, false).unwrap();
+            let stems = glint
+                .layers
+                .iter()
+                .map(|l| stem(cit, Some(l.rule)).unwrap());
+            stems.map(str::to_owned).collect()
+        };
+        // The heavier rule wins the layer, until its texture is missing.
+        assert_eq!(layers(&cit), ["broken"]);
+        let broken = (0..cit.rules.len())
+            .find(|&i| stem(&cit, Some(i)) == Some("broken"))
+            .unwrap();
+        cit.keep_glints(|i| i != broken);
+        assert_eq!(layers(&cit), ["shown"]);
+        assert_eq!(cit.enchantments(&sword, Hand::Main, 0).len(), 1);
+        // None left: vanilla's glint stays.
+        cit.keep_glints(|_| false);
+        assert!(glint(&cit, &sword, false).is_none());
+    }
+
+    #[test]
+    fn an_off_hand_layer_draws_only_in_the_off_hand() {
+        let cit = rules(&[
+            ("left", "type=enchantment\nlayer=1\nhand=off"),
+            ("both", "type=enchantment"),
+        ]);
+        let sword = enchanted("diamond_sword", &[("sharpness", 1)]);
+        let layers = |hand| -> Vec<&str> {
+            let glint = cit.glint(&sword, hand, 0, true).unwrap();
+            glint
+                .layers
+                .iter()
+                .map(|l| stem(&cit, Some(l.rule)).unwrap())
+                .collect()
+        };
+        assert_eq!(layers(Hand::Off), ["both", "left"]);
+        // Asked in this order, a cache keyed without the hand would answer as for the off hand.
+        assert_eq!(layers(Hand::Main), ["both"]);
+    }
 }

crates/horizon-client-render/src/cit_armor.rs

@@ -0,0 +1,319 @@
+//! Custom Item Textures for worn armour and elytra (`type=armor`, `type=elytra`). An armour rule
+//! names its textures after the armour texture files of before 1.21.2
+//! (`textures/models/armor/diamond_layer_1.png`): `texture.diamond_layer_1`,
+//! `texture.leather_layer_2_overlay`..., with `texture` for any layer it does not name. 26.3's
+//! equipment assets name the same layers `entity/equipment/humanoid/diamond` (layer 1: helmet,
+//! chestplate, boots) and `entity/equipment/humanoid_leggings/diamond` (layer 2), so the layers
+//! are mapped back to the old names here. An elytra rule's `texture` replaces the wings'.
+
+use crate::cit_assets::{rule_sprites, sprite_id};
+use horizon_optifine::cit::{Kind, Rule};
+use std::collections::BTreeSet;
+
+/// The pre-1.21.2 armour texture name of an equipment asset's layer: `asset` (`minecraft:gold`
+/// or `gold`) on the leggings layer (`humanoid_leggings`) or the others (`humanoid`), the dye
+/// overlay (`leather_overlay`) or the main texture.
+pub fn armor_layer_name(asset: &str, leggings: bool, overlay: bool) -> String {
+    let path = asset.rsplit_once(':').map_or(asset, |(_, p)| p);
+    // The equipment assets renamed from their old textures; the rest kept their names.
+    let old = match path {
+        "turtle_scute" => "turtle",
+        other => other,
+    };
+    let layer = if leggings { 2 } else { 1 };
+    let suffix = if overlay { "_overlay" } else { "" };
+    format!("{old}_layer_{layer}{suffix}")
+}
+
+/// The texture (a resource path) `rule` draws on the layer named `layer`: its `texture.<layer>`,
+/// else its `texture`.
+pub fn armor_texture<'a>(rule: &'a Rule, layer: &str) -> Option<&'a str> {
+    rule.textures
+        .iter()
+        .find(|(name, _)| name == layer)
+        .map(|(_, path)| path.as_str())
+        .or(rule.texture.as_deref())
+}
+
+/// The atlas name of a CIT texture: its `cit_assets` id, without `minecraft:` as the atlas packs
+/// vanilla's sprites.
+fn atlas_name(resource: &str) -> Option<String> {
+    let id = sprite_id(resource)?;
+    Some(match id.strip_prefix("minecraft:") {
+        Some(name) => name.to_owned(),
+        None => id,
+    })
+}
+
+/// The atlas sprite `rule` puts on the layer of equipment asset `asset` (see
+/// [`armor_layer_name`]); `None` keeps the vanilla texture.
+pub fn layer_sprite(rule: &Rule, asset: &str, leggings: bool, overlay: bool) -> Option<String> {
+    atlas_name(armor_texture(
+        rule,
+        &armor_layer_name(asset, leggings, overlay),
+    )?)
+}
+
+/// The atlas sprite an elytra rule puts on the wings.
+pub fn elytra_sprite(rule: &Rule) -> Option<String> {
+    atlas_name(armor_texture(rule, "elytra")?)
+}
+
+/// The atlas sprite the one CIT armour rule `rule` puts on a worn armour layer: the layer
+/// `vanilla` (an atlas name, `…_overlay` for the dye overlay) of equipment asset `asset` in
+/// equipment layer `kind` (`humanoid_leggings` for the leggings). `None` draws `vanilla`, as does
+/// a name the atlas lacks; nothing is allocated without a rule.
+pub fn worn_layer_sprite(
+    rule: Option<&Rule>,
+    asset: &str,
+    kind: &str,
+    vanilla: &str,
+) -> Option<String> {
+    let leggings = kind == "humanoid_leggings";
+    let overlay = vanilla.ends_with("_overlay");
+    layer_sprite(rule?, asset, leggings, overlay)
+}
+
+/// The CIT elytra rule's wings sprite. On `None`, or a name the atlas lacks, the caller draws the
+/// cape, else the equipment asset's own wings.
+pub fn wings_sprite(rule: Option<&Rule>) -> Option<String> {
+    elytra_sprite(rule?)
+}
+
+/// What a worn layer draws, looked up with `get` (the atlas): the rule's sprite
+/// ([`worn_layer_sprite`]), else `vanilla` when there is no rule or the atlas lacks its texture.
+pub fn worn_layer<R>(
+    rule: Option<&Rule>,
+    asset: &str,
+    kind: &str,
+    vanilla: &str,
+    get: impl Fn(&str) -> Option<R>,
+) -> Option<R> {
+    worn_layer_sprite(rule, asset, kind, vanilla)
+        .and_then(|name| get(&name))
+        .or_else(|| get(vanilla))
+}
+
+/// What worn wings draw, looked up with `get`: the rule's sprite, else the cape; `None` leaves
+/// them to the equipment asset's own wings.
+pub fn wings<R>(
+    rule: Option<&Rule>,
+    cape: Option<&str>,
+    get: impl Fn(&str) -> Option<R>,
+) -> Option<R> {
+    wings_sprite(rule)
+        .and_then(|name| get(&name))
+        .or_else(|| cape.and_then(&get))
+}
+
+/// Sprite ids the armour and elytra rules draw (see [`rule_sprites`]).
+pub fn armor_sprites(rules: &[Rule]) -> BTreeSet<String> {
+    rule_sprites(rules, |kind| matches!(kind, Kind::Armor | Kind::Elytra))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use horizon_optifine::Properties;
+
+    fn rule(path: &str, text: &str) -> Rule {
+        Rule::parse(path, &Properties::parse_equals_first(text), |_| true).unwrap()
+    }
+
+    #[test]
+    fn layers_take_their_old_texture_names() {
+        assert_eq!(
+            armor_layer_name("minecraft:diamond", false, false),
+            "diamond_layer_1"
+        );
+        assert_eq!(armor_layer_name("diamond", true, false), "diamond_layer_2");
+        assert_eq!(
+            armor_layer_name("minecraft:leather", false, true),
+            "leather_layer_1_overlay"
+        );
+        assert_eq!(
+            armor_layer_name("minecraft:leather", true, true),
+            "leather_layer_2_overlay"
+        );
+        assert_eq!(
+            armor_layer_name("minecraft:gold", false, false),
+            "gold_layer_1"
+        );
+        assert_eq!(
+            armor_layer_name("minecraft:chainmail", true, false),
+            "chainmail_layer_2"
+        );
+        assert_eq!(
+            armor_layer_name("minecraft:turtle_scute", false, false),
+            "turtle_layer_1"
+        );
+        assert_eq!(
+            armor_layer_name("minecraft:netherite", true, false),
+            "netherite_layer_2"
+        );
+    }
+
+    #[test]
+    fn a_named_layer_wins_over_the_generic_texture() {
+        let r = rule(
+            "assets/minecraft/optifine/cit/armor/blue.properties",
+            "type=armor\nitems=diamond_chestplate diamond_leggings\ntexture=generic\n\
+             texture.diamond_layer_2=blue_legs\n",
+        );
+        let dir = "assets/minecraft/optifine/cit/armor";
+        assert_eq!(
+            armor_texture(&r, "diamond_layer_2"),
+            Some(format!("{dir}/blue_legs.png").as_str())
+        );
+        assert_eq!(
+            armor_texture(&r, "diamond_layer_1"),
+            Some(format!("{dir}/generic.png").as_str())
+        );
+        assert_eq!(
+            layer_sprite(&r, "minecraft:diamond", true, false).as_deref(),
+            Some("horizon_cit:minecraft/optifine/cit/armor/blue_legs")
+        );
+        assert_eq!(
+            layer_sprite(&r, "minecraft:diamond", false, false).as_deref(),
+            Some("horizon_cit:minecraft/optifine/cit/armor/generic")
+        );
+    }
+
+    #[test]
+    fn without_a_generic_texture_other_layers_stay_vanilla() {
+        let r = rule(
+            "assets/minecraft/optifine/cit/a.properties",
+            "type=armor\nitems=leather_helmet\ntexture.leather_layer_1=dyed\n",
+        );
+        assert_eq!(
+            layer_sprite(&r, "minecraft:leather", false, false).as_deref(),
+            Some("horizon_cit:minecraft/optifine/cit/dyed")
+        );
+        assert_eq!(layer_sprite(&r, "minecraft:leather", false, true), None);
+        assert_eq!(layer_sprite(&r, "minecraft:leather", true, false), None);
+    }
+
+    #[test]
+    fn a_vanilla_texture_path_keeps_its_atlas_name() {
+        let r = rule(
+            "assets/minecraft/optifine/cit/wings.properties",
+            "type=elytra\ntexture=minecraft:textures/entity/wings/dragon.png\n",
+        );
+        assert_eq!(elytra_sprite(&r).as_deref(), Some("entity/wings/dragon"));
+    }
+
+    #[test]
+    fn worn_layers_pick_the_rules_texture_for_their_layer() {
+        let r = rule(
+            "assets/minecraft/optifine/cit/dye.properties",
+            "type=armor\nitems=leather_chestplate leather_leggings\n\
+             texture.leather_layer_1=body\ntexture.leather_layer_1_overlay=body_dye\n\
+             texture.leather_layer_2=legs\n",
+        );
+        let cit = |p: &str| Some(format!("horizon_cit:minecraft/optifine/cit/{p}"));
+        let pick = |kind: &str, vanilla: &str| {
+            worn_layer_sprite(Some(&r), "minecraft:leather", kind, vanilla)
+        };
+        let body = "entity/equipment/humanoid/leather";
+        assert_eq!(pick("humanoid", body), cit("body"));
+        assert_eq!(
+            pick("humanoid", "entity/equipment/humanoid/leather_overlay"),
+            cit("body_dye")
+        );
+        assert_eq!(
+            pick(
+                "humanoid_leggings",
+                "entity/equipment/humanoid_leggings/leather"
+            ),
+            cit("legs")
+        );
+        // No `texture.leather_layer_2_overlay` and no `texture`: the overlay stays vanilla.
+        let legs_dye = "entity/equipment/humanoid_leggings/leather_overlay";
+        assert_eq!(pick("humanoid_leggings", legs_dye), None);
+        // No rule draws vanilla's.
+        assert_eq!(
+            worn_layer_sprite(None, "minecraft:leather", "humanoid", body),
+            None
+        );
+    }
+
+    #[test]
+    fn wings_take_the_rules_texture() {
+        let r = rule(
+            "assets/minecraft/optifine/cit/wings.properties",
+            "type=elytra\ntexture=wings\n",
+        );
+        assert_eq!(
+            wings_sprite(Some(&r)).as_deref(),
+            Some("horizon_cit:minecraft/optifine/cit/wings")
+        );
+        assert_eq!(wings_sprite(None), None);
+    }
+
+    #[test]
+    fn only_armor_and_elytra_rules_reach_the_atlas() {
+        let rules = [
+            rule(
+                "assets/minecraft/optifine/cit/sword.properties",
+                "items=diamond_sword\ntexture=sword\n",
+            ),
+            rule(
+                "assets/minecraft/optifine/cit/plate.properties",
+                "type=armor\nitems=iron_chestplate iron_leggings\ntexture=plate\n\
+                 texture.iron_layer_2=legs\n",
+            ),
+            rule(
+                "assets/minecraft/optifine/cit/wings.properties",
+                "type=elytra\ntexture=wings\n",
+            ),
+            rule(
+                "assets/minecraft/optifine/cit/glint.properties",
+                "type=enchantment\nenchantments=sharpness\ntexture=glint\n",
+            ),
+        ];
+        let got: Vec<String> = armor_sprites(&rules).into_iter().collect();
+        assert_eq!(
+            got,
+            [
+                "horizon_cit:minecraft/optifine/cit/legs",
+                "horizon_cit:minecraft/optifine/cit/plate",
+                "horizon_cit:minecraft/optifine/cit/wings",
+            ]
+        );
+    }
+
+    /// An atlas lookup that knows `names`.
+    fn atlas(names: &[&str]) -> impl Fn(&str) -> Option<String> {
+        let names: Vec<String> = names.iter().map(|n| (*n).to_owned()).collect();
+        move |s| names.iter().any(|n| n == s).then(|| s.to_owned())
+    }
+
+    #[test]
+    fn the_atlas_lookup_falls_back_to_vanilla_and_the_cape() {
+        let iron = rule(
+            "assets/minecraft/optifine/cit/iron.properties",
+            "type=armor\nitems=iron_chestplate\ntexture.iron_layer_1=plate",
+        );
+        let plate = "horizon_cit:minecraft/optifine/cit/plate";
+        let vanilla = "entity/equipment/humanoid/iron";
+        let layer = |rule: Option<&Rule>, names: &[&str]| {
+            worn_layer(rule, "minecraft:iron", "humanoid", vanilla, atlas(names))
+        };
+        assert_eq!(
+            layer(Some(&iron), &[plate, vanilla]).as_deref(),
+            Some(plate)
+        );
+        // The rule's texture didn't reach the atlas, or there's no rule: vanilla's layer.
+        assert_eq!(layer(Some(&iron), &[vanilla]).as_deref(), Some(vanilla));
+        assert_eq!(layer(None, &[plate, vanilla]).as_deref(), Some(vanilla));
+        let elytra = rule(
+            "assets/minecraft/optifine/cit/w.properties",
+            "type=elytra\ntexture=wings",
+        );
+        let w = "horizon_cit:minecraft/optifine/cit/wings";
+        let wing = |rule: Option<&Rule>, names: &[&str]| wings(rule, Some("cape/x"), atlas(names));
+        assert_eq!(wing(Some(&elytra), &[w, "cape/x"]).as_deref(), Some(w));
+        assert_eq!(wing(Some(&elytra), &["cape/x"]).as_deref(), Some("cape/x"));
+        assert_eq!(wings(None, None, atlas(&[w])), None);
+    }
+}

crates/horizon-client-render/src/cit_assets.rs

@@ -5,8 +5,11 @@
 //! `horizon_cit:minecraft/optifine/cit/swords/flame`). A file already under `textures/` (or
 //! `models/`) keeps its vanilla id, so it is not packed twice.
 
+use horizon_assets::model::{CuboidModel, TextureSlot};
 use horizon_optifine::cit::{Kind, Rule};
-use std::collections::BTreeSet;
+use std::collections::{BTreeMap, BTreeSet};
+use std::fs;
+use std::path::Path;
 
 /// The namespace of CIT files outside `textures/` and `models/`.
 pub const NAMESPACE: &str = "horizon_cit";
@@ -55,12 +58,11 @@ pub fn resource(id: &str, ext: &str) -> Option<String> {
     horizon_optifine::paths::valid(rest).then(|| format!("assets/{rest}.{ext}"))
 }
 
-/// Sprite ids the item rules draw: `Kind::Item` rules' `texture` and `texture.<name>` values.
-/// (Textures named by CIT JSON models come in a later PR.) A path no id can name is skipped with
-/// a warning.
-pub fn item_sprites(rules: &[Rule]) -> BTreeSet<String> {
+/// Sprite ids the rules whose kind passes `keep` draw: their `texture` and `texture.<name>`
+/// values. A path no id can name is skipped with a warning.
+pub fn rule_sprites(rules: &[Rule], keep: impl Fn(Kind) -> bool) -> BTreeSet<String> {
     let mut out = BTreeSet::new();
-    for rule in rules.iter().filter(|r| r.kind == Kind::Item) {
+    for rule in rules.iter().filter(|r| keep(r.kind)) {
         let named = rule.textures.iter().map(|(_, path)| path);
         for path in rule.texture.iter().chain(named) {
             match sprite_id(path) {
@@ -77,6 +79,122 @@ pub fn item_sprites(rules: &[Rule]) -> BTreeSet<String> {
     out
 }
 
+/// Sprite ids the item rules draw (`Kind::Item`, see [`rule_sprites`]). Textures named by CIT
+/// JSON models are [`model_sprites`].
+pub fn item_sprites(rules: &[Rule]) -> BTreeSet<String> {
+    rule_sprites(rules, |kind| kind == Kind::Item)
+}
+
+/// The resource path a model value `./x` (or `./../x`, `../x`) names beside the file at `file`,
+/// ending in `.<ext>` (added unless the value has it). `None` for other values and for paths
+/// that would leave the root.
+fn relative(file: &str, value: &str, ext: &str) -> Option<String> {
+    let mut rest = value
+        .strip_prefix("./")
+        .or_else(|| value.starts_with("../").then_some(value))?;
+    let mut dir = file.rsplit_once('/')?.0;
+    while let Some(up) = rest.strip_prefix("../") {
+        dir = dir.rsplit_once('/')?.0;
+        rest = up;
+    }
+    let rest = rest
+        .strip_suffix(ext)
+        .and_then(|r| r.strip_suffix('.'))
+        .unwrap_or(rest);
+    let path = format!("{dir}/{rest}.{ext}");
+    horizon_optifine::paths::valid(&path).then_some(path)
+}
+
+/// The id a relative value of the model at `file` names, as `CuboidModel::from_json` read it
+/// (`./x` is `minecraft:./x` there), with the resource path of the file it names.
+fn rebase(file: &str, id: &str, ext: &str) -> Option<(String, String)> {
+    let path = relative(file, id.strip_prefix("minecraft:")?, ext)?;
+    let id = if ext == "png" {
+        sprite_id(&path)
+    } else {
+        model_id(&path)
+    }?;
+    Some((id, path))
+}
+
+/// Parents followed from a rule's model before the rest are left to the library.
+const MAX_PARENTS: usize = 16;
+
+/// The CIT JSON models the item rules name (`model`, `model.<name>`) under their [`model_id`]s,
+/// with the parents they reach by relative path. Their `./x` texture and parent values become
+/// the ids of the files beside them. Only `horizon_cit` models: the others are in the model
+/// library already. A file that does not read or parse is left out, and a rule's layer that
+/// names it (or a model whose parents reach it) keeps its vanilla model.
+pub fn load_models(root: &Path, rules: &[Rule]) -> BTreeMap<String, CuboidModel> {
+    let mut out = BTreeMap::new();
+    let mut seen = BTreeSet::new();
+    for rule in rules.iter().filter(|r| r.kind == Kind::Item) {
+        let named = rule.models.iter().map(|(_, path)| path);
+        for path in rule.model.iter().chain(named) {
+            load_model(root, path, 0, &mut seen, &mut out);
+        }
+    }
+    out
+}
+
+fn load_model(
+    root: &Path,
+    resource: &str,
+    depth: usize,
+    seen: &mut BTreeSet<String>,
+    out: &mut BTreeMap<String, CuboidModel>,
+) {
+    let Some(id) = model_id(resource) else {
+        log::warn!("custom item textures: {resource} is not a valid model id");
+        return;
+    };
+    let ours = id
+        .strip_prefix(NAMESPACE)
+        .is_some_and(|r| r.starts_with(':'));
+    if !ours || depth > MAX_PARENTS || !seen.insert(id.clone()) {
+        return;
+    }
+    let model = fs::read_to_string(root.join(resource))
+        .map_err(|e| e.to_string())
+        .and_then(|text| CuboidModel::from_json(&text).map_err(|e| e.to_string()));
+    let mut model = match model {
+        Ok(model) => model,
+        Err(e) => {
+            log::warn!("custom item textures: skipped model {resource}: {e}");
+            return;
+        }
+    };
+    for slot in model.textures.values_mut() {
+        if let TextureSlot::Material(m) = slot
+            && let Some((id, _)) = rebase(resource, &m.sprite, "png")
+        {
+            m.sprite = id;
+        }
+    }
+    let parent = model
+        .parent
+        .as_deref()
+        .and_then(|p| rebase(resource, p, "json"));
+    if let Some((id, path)) = parent {
+        model.parent = Some(id);
+        load_model(root, &path, depth + 1, seen, out);
+    }
+    out.insert(id, model);
+}
+
+/// The `horizon_cit` sprites `models` name, which the atlas packs beside [`item_sprites`].
+pub fn model_sprites(models: &BTreeMap<String, CuboidModel>) -> BTreeSet<String> {
+    let prefix = format!("{NAMESPACE}:");
+    models
+        .values()
+        .flat_map(|m| m.textures.values())
+        .filter_map(|slot| match slot {
+            TextureSlot::Material(m) if m.sprite.starts_with(&prefix) => Some(m.sprite.clone()),
+            _ => None,
+        })
+        .collect()
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -161,4 +279,64 @@ mod tests {
             root.join("assets/minecraft/textures/item/stick.png")
         );
     }
+
+    #[test]
+    fn rule_models_load_with_their_relative_textures_and_parents() {
+        let root = std::env::temp_dir().join(format!("horizon-cit-models-{}", std::process::id()));
+        let cit = root.join("assets/minecraft/optifine/cit");
+        fs::create_dir_all(cit.join("swords")).unwrap();
+        let write = |rel: &str, text: &str| fs::write(cit.join(rel), text).unwrap();
+        write(
+            "swords/flame.json",
+            r#"{"parent":"./../base","textures":{"layer0":"./flame","layer1":"item/stick"}}"#,
+        );
+        write(
+            "base.json",
+            r#"{"parent":"item/handheld","textures":{"layer2":"./glow.png"}}"#,
+        );
+        let props =
+            horizon_optifine::Properties::parse_equals_first("items=stick\nmodel=./swords/flame");
+        let rule = Rule::parse("assets/minecraft/optifine/cit/a.properties", &props, |p| {
+            root.join(p).is_file()
+        })
+        .unwrap();
+        let models = load_models(&root, &[rule]);
+        let _ = fs::remove_dir_all(&root);
+        let cit = |p: &str| format!("horizon_cit:minecraft/optifine/cit/{p}");
+        assert_eq!(
+            models.keys().cloned().collect::<Vec<_>>(),
+            [cit("base"), cit("swords/flame")]
+        );
+        let flame = &models[&cit("swords/flame")];
+        assert_eq!(flame.parent.as_deref(), Some(cit("base").as_str()));
+        assert_eq!(
+            models[&cit("base")].parent.as_deref(),
+            Some("minecraft:item/handheld")
+        );
+        assert_eq!(
+            model_sprites(&models).into_iter().collect::<Vec<_>>(),
+            [cit("glow"), cit("swords/flame")]
+        );
+    }
+
+    #[test]
+    fn relative_values_stay_in_the_root() {
+        let file = "assets/minecraft/optifine/cit/a/m.json";
+        let at = |v: &str| relative(file, v, "png");
+        assert_eq!(
+            at("./x").as_deref(),
+            Some("assets/minecraft/optifine/cit/a/x.png")
+        );
+        assert_eq!(
+            at("./../x.png").as_deref(),
+            Some("assets/minecraft/optifine/cit/x.png")
+        );
+        assert_eq!(
+            at("../../x").as_deref(),
+            Some("assets/minecraft/optifine/x.png")
+        );
+        assert_eq!(at("item/x"), None);
+        assert_eq!(at("./../../../../../x"), None);
+        assert_eq!(at("./a/../x"), None);
+    }
 }

crates/horizon-client-render/src/cit_glint.rs

@@ -0,0 +1,386 @@
+//! Custom Item Textures' enchantment glints (`type=enchantment`): which of a stack's matching
+//! rules draw, in which order and how strongly, and whether vanilla's glint still draws under
+//! them. The pack's `cit.properties` (`Global`) says how layers share an item.
+//!
+//! Written from OptiFine's `cit.properties` doc and CIT Resewn's (MIT) `TypeEnchantment` of
+//! before its 1.21.11 port, which implemented `method`, `cap` and `fade`: the sums and the
+//! cycle's fading follow it, except where noted.
+
+pub use horizon_optifine::cit::{Global, Method};
+
+use crate::cit::read_properties;
+use horizon_optifine::cit::Rule;
+use std::path::Path;
+
+/// The pack's global `cit.properties` under the overlay resource root: the first of
+/// `Global::PATHS` that exists, else the defaults.
+pub fn load_global(root: &Path) -> Global {
+    Global::PATHS
+        .iter()
+        .find_map(|path| read_properties(&root.join(path)))
+        .map(|props| Global::parse(&props))
+        .unwrap_or_default()
+}
+
+/// One glint layer a stack draws.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct GlintLayer {
+    /// The rule, an index into `CitRules::rules`.
+    pub rule: usize,
+    /// Its `average` or `layered` share, 1 under `none` and `cycle`.
+    pub weight: f32,
+    /// Its `duration`, for `cycle`.
+    duration: f32,
+}
+
+/// What a stack's glint is made of, worked out when the stack changes.
+#[derive(Clone, Debug, Default, PartialEq)]
+pub struct StackGlint {
+    /// Bottom first (`layer` ascending).
+    pub layers: Vec<GlintLayer>,
+    /// Whether vanilla's glint draws (on a stack that has one) under the layers.
+    pub vanilla: bool,
+    /// `fade` when the layers take turns (`method=cycle`).
+    cycle_fade: Option<f32>,
+}
+
+impl StackGlint {
+    /// The layers among `matched` (the stack's matching enchantment rules, in priority order,
+    /// as `CitRules::enchantments` gives them) that draw, for a stack with `enchantments`
+    /// (`ItemStack::crafting_enchantments`).
+    pub fn new(
+        rules: &[Rule],
+        matched: &[usize],
+        enchantments: &[(impl AsRef<str>, u32)],
+        global: &Global,
+    ) -> Self {
+        // The highest priority rule of each layer.
+        let mut layers: Vec<usize> = Vec::new();
+        for &i in matched {
+            let layer = rules[i].glint.layer;
+            if !layers.iter().any(|&j| rules[j].glint.layer == layer) {
+                layers.push(i);
+            }
+        }
+        layers.sort_by_key(|&i| rules[i].glint.layer);
+        let cycle = global.method == Method::Cycle;
+        // OptiFine's doc: `cap` is for `average` and `layered`, and keeps the topmost layers.
+        // `none`, which OptiFine lacks, is capped too, as CIT Resewn caps every method (it keeps
+        // the bottom layers, though, and caps cycles as well).
+        if let Some(cap) = global.cap.filter(|_| !cycle) {
+            let cap = usize::try_from(cap).unwrap_or(usize::MAX);
+            layers = layers.split_off(layers.len().saturating_sub(cap));
+        }
+        // CIT Resewn: any layer left asking for vanilla's glint keeps it, and the global
+        // `useGlint=false` removes it everywhere, as OptiFine's doc says too. `cap=0` leaves no
+        // custom layer, and vanilla's glint only if the pack's `useGlint` allows it.
+        let vanilla = global.use_glint
+            && (layers.is_empty() || layers.iter().any(|&i| rules[i].glint.use_glint));
+        // CIT Resewn: shares are against every enchantment of the stack, not only those the
+        // layers name.
+        let levels = enchantments.iter().map(|(_, level)| *level as f32);
+        let total = match global.method {
+            Method::Average => levels.sum::<f32>(),
+            Method::Layered => levels.fold(0.0, f32::max),
+            Method::None | Method::Cycle => 0.0,
+        };
+        let shared = matches!(global.method, Method::Average | Method::Layered);
+        let layers = layers
+            .into_iter()
+            .map(|i| {
+                let rule = &rules[i];
+                let named = &rule.enchantments;
+                let weight = if !shared || named.is_empty() {
+                    1.0
+                } else {
+                    // The highest level among the enchantments the rule names whose level also
+                    // passes its `enchantmentLevels` (CIT Resewn takes the first named one the
+                    // stack has, whatever its level).
+                    let in_range = |level: u32| {
+                        let level = i32::try_from(level).unwrap_or(i32::MAX);
+                        rule.enchantment_levels
+                            .as_ref()
+                            .is_none_or(|r| r.contains(level))
+                    };
+                    let level = enchantments
+                        .iter()
+                        .filter(|(id, level)| {
+                            let id: &str = id.as_ref();
+                            named.iter().any(|n| n == id) && in_range(*level)
+                        })
+                        .map(|(_, level)| *level as f32)
+                        .fold(0.0, f32::max);
+                    if total > 0.0 { level / total } else { 0.0 }
+                };
+                GlintLayer {
+                    rule: i,
+                    weight,
+                    duration: rule.glint.duration,
+                }
+            })
+            .collect();
+        Self {
+            layers,
+            vanilla,
+            cycle_fade: cycle.then_some(global.fade),
+        }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.layers.is_empty()
+    }
+
+    /// Layer `index`'s intensity `seconds` into the game: its weight, and under `method=cycle`
+    /// its turn.
+    pub fn intensity(&self, index: usize, seconds: f64) -> f32 {
+        let layer = self.layers[index];
+        match self.cycle_fade {
+            None => layer.weight,
+            Some(fade) => cycle_intensity(&self.layers, fade, index, seconds),
+        }
+    }
+}
+
+/// CIT Resewn's `Loops.statelessFadingLoop`: each layer shows alone for its `duration`, then
+/// fades into the next over `fade` seconds, the last into the first. With no time at all
+/// (every `duration` and `fade` 0) the bottom layer shows alone.
+fn cycle_intensity(layers: &[GlintLayer], fade: f32, index: usize, seconds: f64) -> f32 {
+    let n = layers.len();
+    let fade = f64::from(fade);
+    let period: f64 = layers.iter().map(|l| f64::from(l.duration) + fade).sum();
+    if n == 1 || period <= 0.0 {
+        return if index == 0 { 1.0 } else { 0.0 };
+    }
+    let mut t = seconds.rem_euclid(period);
+    for (i, layer) in layers.iter().enumerate() {
+        let duration = f64::from(layer.duration);
+        if t < duration {
+            return if i == index { 1.0 } else { 0.0 };
+        }
+        t -= duration;
+        // Defensive: the last fade also takes anything rounding might leave of the period
+        // (none seen), ending fully on the first layer.
+        if t < fade || i + 1 == n {
+            let into = if fade > 0.0 {
+                (t / fade).min(1.0) as f32
+            } else {
+                1.0
+            };
+            return if i == index {
+                1.0 - into
+            } else if (i + 1) % n == index {
+                into
+            } else {
+                0.0
+            };
+        }
+        t -= fade;
+    }
+    // Not reached, as the last layer returns above; no layer rather than a panic.
+    0.0
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use horizon_optifine::Properties;
+
+    const DIR: &str = "assets/minecraft/optifine/cit";
+
+    /// An enchantment rule named `name` with `text` after `type` and `texture`.
+    fn rule(name: &str, text: &str) -> Rule {
+        let text = format!("type=enchantment\ntexture=glint\n{text}");
+        let path = format!("{DIR}/{name}.properties");
+        Rule::parse(&path, &Properties::parse_equals_first(&text), |_| true).unwrap()
+    }
+
+    fn global(text: &str) -> Global {
+        Global::parse(&Properties::parse_equals_first(text))
+    }
+
+    fn rules_of(layers: &StackGlint) -> Vec<usize> {
+        layers.layers.iter().map(|l| l.rule).collect()
+    }
+
+    const SWORD: [(&str, u32); 2] = [("minecraft:sharpness", 3), ("minecraft:unbreaking", 1)];
+
+    #[test]
+    fn one_rule_per_layer_bottom_first() {
+        let rules = [
+            rule("a", "layer=2"),
+            rule("b", "layer=0"),
+            rule("c", "layer=2"),
+            rule("d", "layer=-1"),
+        ];
+        // Priority order a, b, c, d: c loses layer 2 to a.
+        let g = StackGlint::new(&rules, &[0, 1, 2, 3], &SWORD, &Global::default());
+        assert_eq!(rules_of(&g), [3, 1, 0]);
+        let g = StackGlint::new(&rules, &[2, 0], &SWORD, &Global::default());
+        assert_eq!(rules_of(&g), [2]);
+    }
+
+    #[test]
+    fn average_and_layered_shares() {
+        let rules = [
+            rule("sharp", "enchantments=sharpness smite"),
+            rule("unb", "layer=1\nenchantments=unbreaking"),
+            rule("any", "layer=2"),
+            rule("fire", "layer=3\nenchantments=fire_aspect"),
+        ];
+        let weights = |method: &str| {
+            let g = StackGlint::new(&rules, &[0, 1, 2, 3], &SWORD, &global(method));
+            g.layers.iter().map(|l| l.weight).collect::<Vec<_>>()
+        };
+        // Sharpness III and Unbreaking I: 3 / 4 and 1 / 4; against the highest, 3 / 3 and 1 / 3.
+        // A rule naming no enchantment is at full strength, one the stack lacks at none.
+        assert_eq!(weights("method=average"), [0.75, 0.25, 1.0, 0.0]);
+        assert_eq!(weights("method=layered"), [1.0, 1.0 / 3.0, 1.0, 0.0]);
+        assert_eq!(weights("method=cycle"), [1.0; 4]);
+        assert_eq!(weights("method=none"), [1.0; 4]);
+    }
+
+    #[test]
+    fn the_level_is_one_the_rules_levels_allow() {
+        let rules = [rule(
+            "holy",
+            "enchantments=sharpness smite\nenchantmentLevels=1-2",
+        )];
+        // Sharpness V is out of range, so Smite I sets the share: 1 / 5 of the highest level.
+        let stack = [("minecraft:sharpness", 5), ("minecraft:smite", 1)];
+        let g = StackGlint::new(&rules, &[0], &stack, &global("method=layered"));
+        assert_eq!(g.layers[0].weight, 1.0 / 5.0);
+    }
+
+    #[test]
+    fn cap_keeps_the_topmost_layers() {
+        let rules = [
+            rule("a", "layer=0"),
+            rule("b", "layer=1"),
+            rule("c", "layer=2"),
+        ];
+        let g = StackGlint::new(&rules, &[0, 1, 2], &SWORD, &global("cap=2"));
+        assert_eq!(rules_of(&g), [1, 2]);
+        let g = StackGlint::new(&rules, &[0, 1, 2], &SWORD, &global("cap=0"));
+        assert!(g.is_empty());
+        let g = StackGlint::new(&rules, &[0, 1, 2], &SWORD, &global("cap=1\nmethod=none"));
+        assert_eq!(rules_of(&g), [2]);
+        // Cycles show every layer in turn.
+        let g = StackGlint::new(&rules, &[0, 1, 2], &SWORD, &global("cap=1\nmethod=cycle"));
+        assert_eq!(rules_of(&g), [0, 1, 2]);
+    }
+
+    #[test]
+    fn vanilla_glint() {
+        let plain = rule("plain", "");
+        let keep = rule("keep", "layer=1\nuseGlint=true");
+        let rules = [plain, keep];
+        let vanilla = |matched: &[usize], text: &str| {
+            StackGlint::new(&rules, matched, &SWORD, &global(text)).vanilla
+        };
+        assert!(vanilla(&[], ""), "no rule: vanilla's glint");
+        assert!(!vanilla(&[0], ""), "a rule replaces it");
+        assert!(vanilla(&[0, 1], ""), "unless one keeps it");
+        assert!(!vanilla(&[], "useGlint=false"));
+        assert!(!vanilla(&[1], "useGlint=false"), "the pack's word is final");
+        // Only the layers `cap` keeps count.
+        let rules = [rule("keep", "useGlint=true"), rule("top", "layer=1")];
+        let g = StackGlint::new(&rules, &[0, 1], &SWORD, &global("cap=1"));
+        assert!(!g.vanilla);
+        let g = StackGlint::new(&rules, &[0, 1], &SWORD, &global("cap=0"));
+        assert!(g.is_empty() && g.vanilla);
+        let g = StackGlint::new(&rules, &[0, 1], &SWORD, &global("cap=0\nuseGlint=false"));
+        assert!(!g.vanilla);
+    }
+
+    #[test]
+    fn cycles_take_turns_and_fade() {
+        let rules = [
+            rule("a", "duration=2"),
+            rule("b", "layer=1\nduration=1"),
+            rule("c", "layer=2\nduration=1"),
+        ];
+        let g = StackGlint::new(
+            &rules,
+            &[0, 1, 2],
+            &SWORD,
+            &global("method=cycle\nfade=0.5"),
+        );
+        // a 0-2, a→b 2-2.5, b 2.5-3.5, b→c 3.5-4, c 4-5, c→a 5-5.5, then again.
+        let at = |t: f64| [0, 1, 2].map(|i| g.intensity(i, t));
+        assert_eq!(at(1.0), [1.0, 0.0, 0.0]);
+        assert_eq!(at(2.125), [0.75, 0.25, 0.0]);
+        assert_eq!(at(3.0), [0.0, 1.0, 0.0]);
+        assert_eq!(at(3.75), [0.0, 0.5, 0.5]);
+        assert_eq!(at(4.5), [0.0, 0.0, 1.0]);
+        assert_eq!(at(5.25), [0.5, 0.0, 0.5]);
+        assert_eq!(at(5.5 + 3.0), [0.0, 1.0, 0.0]);
+        // One layer always shows.
+        let one = StackGlint::new(&rules, &[1], &SWORD, &global("method=cycle"));
+        assert_eq!(one.intensity(0, 0.7), 1.0);
+    }
+
+    #[test]
+    fn a_cycle_always_shows_a_whole_layer() {
+        let rules = [
+            rule("a", "duration=0.1"),
+            rule("b", "layer=1\nduration=0.7"),
+            rule("c", "layer=2\nduration=0.2"),
+        ];
+        let g = StackGlint::new(
+            &rules,
+            &[0, 1, 2],
+            &SWORD,
+            &global("method=cycle\nfade=0.3"),
+        );
+        // Every millisecond of the first two seconds, and just under a period, the last fade's
+        // end. (Rounding has not been seen to leave time past it; the last fade's clamp is
+        // defensive.)
+        let period: f64 = [0.1f32, 0.7, 0.2]
+            .map(|d| f64::from(d) + f64::from(0.3f32))
+            .iter()
+            .sum();
+        let last = f64::from_bits(period.to_bits() - 1);
+        for t in (0..2000_i32)
+            .map(|i| f64::from(i) * 0.001)
+            .chain([last, period + last])
+        {
+            let sum: f32 = (0..3).map(|i| g.intensity(i, t)).sum();
+            assert!((sum - 1.0).abs() < 1e-5, "{sum} at {t}");
+        }
+        // No time at all: the bottom layer alone, never NaN.
+        let still = [rule("a", "duration=0"), rule("b", "layer=1\nduration=0")];
+        let g = StackGlint::new(&still, &[0, 1], &SWORD, &global("method=cycle\nfade=0"));
+        for t in [0.0, 0.5, 7.25] {
+            assert_eq!([0, 1].map(|i| g.intensity(i, t)), [1.0, 0.0]);
+        }
+    }
+
+    #[test]
+    fn the_first_global_file_wins() {
+        let root = std::env::temp_dir().join(format!("horizon-cit-glint-{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&root);
+        assert_eq!(load_global(&root), Global::default());
+        let write = |path: &str, text: &[u8]| {
+            let file = root.join(path);
+            std::fs::create_dir_all(file.parent().unwrap()).unwrap();
+            std::fs::write(file, text).unwrap();
+        };
+        // Saved as Latin-1 (`é` is not UTF-8 alone), in the OptiFine doc's `cit/` folder.
+        write(
+            "assets/minecraft/optifine/cit/cit.properties",
+            b"# caf\xE9\nmethod=cycle",
+        );
+        assert_eq!(load_global(&root).method, Method::Cycle);
+        write("assets/minecraft/mcpatcher/cit.properties", b"method=none");
+        assert_eq!(load_global(&root).method, Method::Cycle);
+        write(
+            "assets/minecraft/optifine/cit.properties",
+            b"method=layered",
+        );
+        assert_eq!(load_global(&root).method, Method::Layered);
+        write("assets/minecraft/citresewn/cit.properties", b"cap=1");
+        let g = load_global(&root);
+        let _ = std::fs::remove_dir_all(&root);
+        assert_eq!((g.method, g.cap), (Method::Average, Some(1)));
+    }
+}

crates/horizon-client-render/src/connected.rs

@@ -387,7 +387,8 @@ impl ConnectedTextures {
 
     /// What the `face` of the block `state` at `pos` draws, for a quad with sprite `layer`.
     /// `neighbour` answers the state at an offset from the block; `biome` its biome, asked only
-    /// by rules that test one.
+    /// by rules that test one; `texture` the quad's own texture directions, asked only by rules
+    /// with `orient=texture`.
     pub fn pick<'b>(
         &self,
         state: u32,
@@ -396,6 +397,7 @@ impl ConnectedTextures {
         pos: [i32; 3],
         neighbour: impl Fn([i32; 3]) -> u32,
         biome: impl Fn() -> Option<&'b str>,
+        texture: impl Fn() -> Option<Axes>,
         mut overlay: impl FnMut(Overlay),
     ) -> Pick {
         let (mut by_state, mut by_layer) = (
@@ -427,9 +429,58 @@ impl ConnectedTextures {
             let r = &self.rules[usize::from(i)];
             if (block || r.rule.match_blocks.is_empty())
                 && (tile || r.rule.match_tiles.is_empty())
-                && let Some(pick) =
-                    self.apply(r, state, layer, face, pos, &neighbour, &biome, &mut overlay)
+                && let Some(pick) = self.apply(
+                    r,
+                    state,
+                    layer,
+                    face,
+                    pos,
+                    &neighbour,
+                    &biome,
+                    &texture,
+                    &mut overlay,
+                )
             {
+                // "Tiles output by CTM rules can also be matched by another rule": once, by the
+                // tile rules naming the picked tile (and this block, if they name blocks).
+                // A tile on the face's own sprite (`tiles=stone`) is no new tile.
+                let Pick::Tile(TileLayer::Layer { layer: picked, .. }) = pick else {
+                    return pick;
+                };
+                if picked == layer {
+                    return pick;
+                }
+                let own = self.list(&self.by_state, state as usize);
+                // Rules tried on the face's sprite already (those before this one) are not tried
+                // again: an overlay would draw twice.
+                let first = self.list(&self.by_layer, layer as usize);
+                let again = self
+                    .list(&self.by_layer, picked as usize)
+                    .iter()
+                    .map(|&j| (j, &self.rules[usize::from(j)]))
+                    .filter(|&(j, r)| {
+                        j != i
+                            && !(j < i && first.contains(&j))
+                            && (r.rule.match_blocks.is_empty() || own.contains(&j))
+                    });
+                for (_, r) in again {
+                    // Joins by tile still compare the face's own sprite with its neighbours'.
+                    match self.apply(
+                        r,
+                        state,
+                        layer,
+                        face,
+                        pos,
+                        &neighbour,
+                        &biome,
+                        &texture,
+                        &mut overlay,
+                    ) {
+                        Some(Pick::Keep) => return pick,
+                        Some(chained) => return chained,
+                        None => {}
+                    }
+                }
                 return pick;
             }
         }
@@ -447,6 +498,7 @@ impl ConnectedTextures {
         pos: [i32; 3],
         neighbour: &impl Fn([i32; 3]) -> u32,
         biome: &impl Fn() -> Option<&'b str>,
+        texture: &impl Fn() -> Option<Axes>,
         overlay: &mut impl FnMut(Overlay),
     ) -> Option<Pick> {
         let rule = &r.rule;
@@ -487,7 +539,12 @@ impl ConnectedTextures {
         };
         let axes = |face| match (rule.orient, info.axis) {
             (Orient::StateAxis, Some(axis)) => Axes::column(face, axis),
-            // `orient=texture` follows the quad's own UVs; vanilla cubes are what it is used on.
+            // The quad's own texture directions, whatever face `symmetry` stands it for.
+            // Not for `overlay`, which Continuity's `orient` leaves out: its 17 tiles always face
+            // the standard way.
+            (Orient::Texture, _) if rule.method != Method::Overlay => {
+                texture().unwrap_or(Axes::cube(face))
+            }
             _ => Axes::cube(face),
         };
         let mask = || geometry::neighbours(axes(face), face.normal(), rule.inner_seams, joins);
@@ -649,6 +706,10 @@ mod tests {
             |name| match name {
                 "minecraft:block/stone" => Some(7),
                 "minecraft:block/glass" => Some(3),
+                // The tile `b0` of a rule second in order (`a_picked_tile_can_be_picked_again`).
+                "assets/minecraft/optifine/ctm/b0.png" => Some(2000),
+                // And `a0` of the first rule.
+                "assets/minecraft/optifine/ctm/a0.png" => Some(1000),
                 _ => None,
             },
         )
@@ -671,7 +732,7 @@ mod tests {
         blocks: &[([i32; 3], u32)],
     ) -> Pick {
         let at = |o: [i32; 3]| blocks.iter().find(|(p, _)| *p == o).map_or(0, |b| b.1);
-        ctm.pick(state, layer, face, [0, 64, 0], at, || None, |_| {})
+        ctm.pick(state, layer, face, [0, 64, 0], at, || None, || None, |_| {})
     }
 
     const GLASS: &str = "matchBlocks=glass\nmethod=ctm\ntiles=0-46";
@@ -794,8 +855,26 @@ mod tests {
         )]);
         let mut tiles = std::collections::HashSet::new();
         for x in 0..20 {
-            let lower = ctm.pick(5, 3, Face::North, [x, 64, 0], |_| 0, || None, |_| {});
-            let upper = ctm.pick(6, 3, Face::North, [x, 65, 0], |_| 0, || None, |_| {});
+            let lower = ctm.pick(
+                5,
+                3,
+                Face::North,
+                [x, 64, 0],
+                |_| 0,
+                || None,
+                || None,
+                |_| {},
+            );
+            let upper = ctm.pick(
+                6,
+                3,
+                Face::North,
+                [x, 65, 0],
+                |_| 0,
+                || None,
+                || None,
+                |_| {},
+            );
             assert_eq!(lower, upper, "{x}");
             tiles.insert(format!("{lower:?}"));
         }
@@ -809,7 +888,16 @@ mod tests {
             "matchBlocks=glass\nmethod=fixed\ntiles=0\nheights=0-63\nbiomes=desert",
         )]);
         let at = |y, biome: &'static str| {
-            ctm.pick(1, 3, Face::Up, [0, y, 0], |_| 0, || Some(biome), |_| {})
+            ctm.pick(
+                1,
+                3,
+                Face::Up,
+                [0, y, 0],
+                |_| 0,
+                || Some(biome),
+                || None,
+                |_| {},
+            )
         };
         assert_eq!(at(10, "minecraft:desert"), tile(1000));
         assert_eq!(at(64, "minecraft:desert"), Pick::Keep);
@@ -844,7 +932,7 @@ mod tests {
             "glass.properties",
             "matchBlocks=glass\nmethod=repeat\nwidth=2\nheight=2\ntiles=0-3",
         )]);
-        let at = |pos| ctm.pick(1, 3, Face::North, pos, |_| 0, || None, |_| {});
+        let at = |pos| ctm.pick(1, 3, Face::North, pos, |_| 0, || None, || None, |_| {});
         assert_eq!(at([0, 64, 0]), tile(1000));
         // The north face's right is west; rows run down.
         assert_eq!(at([-1, 64, 0]), tile(1001));
@@ -925,6 +1013,7 @@ mod tests {
             [0, 64, 0],
             at,
             || None,
+            || None,
             |o| out.push(o.layer),
         );
         (out, pick)
@@ -962,6 +1051,7 @@ mod tests {
             [0, 64, 0],
             |o| if o == [0, 0, -1] { 1 } else { 0 },
             || None,
+            || None,
             |o| {
                 tint = Some((o.tint, o.translucent));
             },
@@ -999,6 +1089,7 @@ mod tests {
             [0, 64, 0],
             door_north,
             || None,
+            || None,
             |o| got.push(o),
         );
         assert_eq!(
@@ -1039,6 +1130,99 @@ mod tests {
         assert_eq!((layers, pick), (vec![1001, 3000], Pick::Keep));
     }
 
+    #[test]
+    fn a_picked_tile_can_be_picked_again() {
+        // b (rule 1) gives glass its tile b0, layer 2000; t (rule 0, a tile rule, tried first)
+        // names that tile, so it draws in b0's place.
+        let chain = |t: &str| {
+            world(&[
+                ("b.properties", "matchBlocks=glass\nmethod=fixed\ntiles=b0"),
+                ("t.properties", t),
+            ])
+        };
+        let ctm = chain("matchTiles=optifine/ctm/b0.png\nmethod=fixed\ntiles=0");
+        assert_eq!(pick_in(&ctm, 1, 3, Face::Up, &[]), tile(1000));
+        // A chained rule keeping the tile (<default>) leaves b's.
+        let ctm = chain("matchTiles=optifine/ctm/b0.png\nmethod=fixed\ntiles=<default>");
+        assert_eq!(pick_in(&ctm, 1, 3, Face::Up, &[]), tile(2000));
+        // One that names another block doesn't chain on glass.
+        let ctm = chain("matchTiles=optifine/ctm/b0.png\nmatchBlocks=stone\nmethod=fixed\ntiles=0");
+        assert_eq!(pick_in(&ctm, 1, 3, Face::Up, &[]), tile(2000));
+        // An overlay tried on the face's own sprite and on the picked tile draws once.
+        let ctm = chain("matchTiles=glass optifine/ctm/b0.png\nmethod=overlay_fixed\ntiles=0");
+        let (overlays, pick) = overlays_in(&ctm, 1, Face::Up, &[]);
+        assert_eq!((overlays, pick), (vec![1000], tile(2000)));
+        // A rule after the one that picked, naming both the face's sprite and the tile, wasn't
+        // tried: it chains.
+        let ctm = world(&[
+            ("a.properties", "matchTiles=glass\nmethod=fixed\ntiles=a0"),
+            (
+                "c.properties",
+                "matchTiles=glass optifine/ctm/a0.png\nmethod=fixed\ntiles=0",
+            ),
+        ]);
+        assert_eq!(pick_in(&ctm, 1, 3, Face::Up, &[]), tile(2000));
+    }
+
+    #[test]
+    fn orient_texture_follows_the_quads_uvs() {
+        let rule = |orient: &str| {
+            world(&[(
+                "glass.properties",
+                &*format!("matchBlocks=glass\nmethod=horizontal\ntiles=0-3\norient={orient}"),
+            )])
+        };
+        // A mirrored north face (a vanilla pane's): its texture's right is east.
+        let mirrored = || {
+            Some(Axes {
+                right: [1, 0, 0],
+                up: [0, 1, 0],
+            })
+        };
+        let east = |o: [i32; 3]| if o == [1, 0, 0] { 1 } else { 0 };
+        let at = |ctm: &ConnectedTextures| {
+            ctm.pick(
+                1,
+                3,
+                Face::North,
+                [0, 64, 0],
+                east,
+                || None,
+                mirrored,
+                |_| {},
+            )
+        };
+        // Glass to the east is to the texture's right: the row's left end.
+        assert_eq!(at(&rule("texture")), tile(1000));
+        // By the cube's directions it is to the left: the row's right end.
+        assert_eq!(at(&rule("none")), tile(1002));
+        // A plain overlay keeps the standard directions: glass north of a top face is above it
+        // (tile 15) whatever the quad's texture says.
+        let overlay = world(&[(
+            "a.properties",
+            "matchBlocks=stone\nmethod=overlay\nconnectBlocks=glass\ntiles=0-16\norient=texture",
+        )]);
+        let turned = || {
+            Some(Axes {
+                right: [0, 0, 1],
+                up: [1, 0, 0],
+            })
+        };
+        let north = |o: [i32; 3]| if o == [0, 0, -1] { 1 } else { 0 };
+        let mut got = Vec::new();
+        overlay.pick(
+            2,
+            7,
+            Face::Up,
+            [0, 64, 0],
+            north,
+            || None,
+            turned,
+            |o| got.push(o.layer),
+        );
+        assert_eq!(got, [1015]);
+    }
+
     #[test]
     fn stacked_panes_hide_the_strips_they_share() {
         let props = |pairs: &[(&str, &str)]| -> BlockProperties {

crates/horizon-client-render/src/entity.wgsl

@@ -31,6 +31,9 @@ struct Globals {
     // HDR output's tier windows (hdr.rs `Hdr::windows`): x..w low to very bright,
     // [0] where the lift starts, [1] where it is full.
     hdr_windows: array<vec4<f32>, 2>,
+    // HDR lighting: x how strongly the sky lights the world now (`Sky::sky_light_factor`),
+    // y what the sky and fog get: the same, but none under water.
+    hdr_light: vec4<f32>,
 }
 @group(0) @binding(0) var<uniform> globals: Globals;
 @group(0) @binding(1) var atlas: texture_2d<f32>;
@@ -69,6 +72,8 @@ struct Out {
     // HDR tier of a light-giving particle (mesher::hdr_tier), from the overlay's
     // high bits (particles.rs): fs_hdr_mark marks the frame with it.
     @location(13) @interpolate(flat) tier: u32,
+    // HDR lighting (`hdr_scene`), 0 for what isn't lit.
+    @location(14) scene: f32,
 }
 // Shipped light.glsl; normals are already transformed and RGBA8_SNORM packed.
 fn entity_light(normal: vec3<f32>, nether: bool) -> f32 {
@@ -107,6 +112,16 @@ fn native_colored_light(pos: vec3<f32>) -> vec3<f32> {
     }
     return min(rgb, vec3(1.0));
 }
+// HDR lighting: how far an entity's light carries it above paper white, 0 to 1, as terrain's.
+fn hdr_scene(block: f32, sky: f32) -> f32 {
+    let b = smoothstep(11.0, 15.0, block);
+    let s = smoothstep(11.0, 15.0, sky) * globals.hdr_light.x;
+    return max(b, s);
+}
+// The frame's alpha for it, between 1 (none) and the light sources' marks below 0.75.
+fn hdr_scene_alpha(scene: f32) -> f32 {
+    return 1.0 - 0.24 * scene;
+}
 fn entity_vertex(position: vec3<f32>, uv: vec2<f32>,
     overlay: u32, color: vec4<f32>, light: vec4<u32>, normal: vec4<f32>) -> Out {
     var out: Out;
@@ -120,6 +135,7 @@ fn entity_vertex(position: vec3<f32>, uv: vec2<f32>,
     let unlit = overlay == 2u || overlay == 4u || overlay == 6u || overlay == 9u || overlay == 10u
         || overlay == 11u || overlay == 12u;
     out.light_color = select(lm, vec4(1.0), unlit);
+    out.scene = select(hdr_scene(l.x / 16.0, l.y / 16.0), 0.0, unlit);
     if globals.colored_count.x > 0u && !unlit {
         out.light_color = vec4(min(out.light_color.rgb + native_colored_light(position), vec3(1.0)), out.light_color.a);
     }
@@ -328,8 +344,14 @@ fn shadow_color(in: Out) -> vec4<f32> {
     var uv = in.uv;
     if in.overlay == 6u { uv.y = in.wrap.x + fract(in.uv.y) * in.wrap.y; }
     let texel = textureSample(atlas, atlas_sampler, uv);
-    if in.tier == 0u || texel.a < 0.1 { discard; }
-    return vec4(0.0, 0.0, 0.0, hdr_mark(in.tier, brightness(texel.rgb * in.color.rgb)));
+    if texel.a < 0.1 { discard; }
+    // Fog hides a light source and the light on a surface as it hides everything else.
+    let fogged = max(linear_fog(in.spherical, globals.fog.x, globals.fog.y),
+        linear_fog(in.cylindrical, globals.fog.z, globals.fog.w)) * globals.fog_color.a;
+    if in.tier == 0u {
+        return vec4(0.0, 0.0, 0.0, hdr_scene_alpha(mix(in.scene, globals.hdr_light.y, fogged)));
+    }
+    return vec4(0.0, 0.0, 0.0, hdr_mark(in.tier, brightness(texel.rgb * in.color.rgb) * (1.0 - fogged)));
 }
 fn brightness(c: vec3<f32>) -> f32 {
     let l = pow(max(c, vec3(0.0)), vec3(2.2));
@@ -348,7 +370,7 @@ fn hdr_mark(tier: u32, y: f32) -> f32 {
 // no longer shines; fs_hdr_mark then marks the light sources it holds.
 @fragment fn fs_hdr_hand_unmark(in: Out) -> @location(0) vec4<f32> {
     if textureSample(atlas, atlas_sampler, in.uv).a < 0.1 { discard; }
-    return vec4(0.0, 0.0, 0.0, 1.0);
+    return vec4(0.0, 0.0, 0.0, hdr_scene_alpha(in.scene));
 }
 
 fn celestial_color(in: Out) -> vec4<f32> {
@@ -375,8 +397,12 @@ fn celestial_color(in: Out) -> vec4<f32> {
     let added = color.rgb * color.a;
     // The sun at the brightest tier, the moon at its own (in.tier); geometry that sets
     // none (the End sky, the End flash) stays brightest.
-    let keep = 1.0 - hdr_mark(select(in.tier, 4u, in.tier == 0u), brightness(added));
-    return vec4(added, keep * smoothstep(0.1, 0.3, max(added.r, max(added.g, added.b))));
+    let tier = select(in.tier, 4u, in.tier == 0u);
+    let y = brightness(added);
+    // Only what's past the tier's window takes the mark: a soft edge keeps the sky's light,
+    // or it would come out darker than the sky around it.
+    if y < globals.hdr_windows[1][clamp(tier, 1u, 4u) - 1u] { return vec4(added, 0.0); }
+    return vec4(added, 1.0 - hdr_mark(tier, y));
 }
 
 // RenderPipelines.ENERGY_SWIRL (entity.fsh with EMISSIVE and NO_OVERLAY): the sprite, scrolled by

crates/horizon-client-render/src/font.rs

@@ -947,6 +947,16 @@ impl Font {
             .sum::<f32>()
             .ceil()
     }
+    /// `Font.width(FormattedCharSequence)` of a sequence a component built
+    /// with `FormattedCharSequence.forward`: every character is a glyph, a
+    /// `§` included (`StringDecomposer.iterate`, not `iterateFormatted`).
+    pub fn width_drawn(&self, t: &Text) -> f32 {
+        crate::bidi::visual(t)
+            .chars()
+            .map(|(c, s)| self.advance(c, s))
+            .sum::<f32>()
+            .ceil()
+    }
     /// `StringSplitter.splitLines`: each line and whether it continues a
     /// wrapped one. A line breaks at a `\n`, or once a character overflows
     /// `max_width` (never the first visible one) at the last space so far, or

crates/horizon-client-render/src/gfx.rs

@@ -112,6 +112,7 @@ mod cull;
 mod end_sky;
 mod flat;
 mod frame_gen;
+mod gpu_lists;
 mod hdr;
 mod hdr_icc;
 mod hdr_stats;
@@ -145,6 +146,7 @@ mod page_runs;
 pub mod panorama;
 mod readback;
 mod resident;
+mod reuse;
 mod stars;
 pub mod submit;
 mod sunrise_fan;
@@ -328,6 +330,7 @@ struct Globals {
     /// HDR output's tier windows, low to very bright: where the lift starts, where it is
     /// full (`hdr::Hdr::windows`); zero without HDR.
     hdr_windows: [[f32; 4]; 2],
+    hdr_light: [f32; 4],
 }
 pub type SectionKey = (i32, i32, i32);
 /// The water mirror's targets: the world as a camera mirrored about the water plane sees
@@ -355,6 +358,8 @@ struct SectionGpu {
     sorted_indices: Option<(u32, u64)>,
     /// Its id for flat draws (`flat::Flat::add`), when they are on.
     flat_id: Option<u32>,
+    /// Its row for phase 1's lists made on the GPU (`gpu_lists::GpuLists::add`).
+    list_id: Option<u32>,
     /// When it began to fade in over the far terrain it replaces, which
     /// stays whole behind it until then: a section new where far tiles are
     /// drawn. Meshed again, it stays as it was.
@@ -445,12 +450,19 @@ impl Part {
 /// hold on `page` of `arena` (`part`) goes to its other pages in video memory,
 /// until the next range would pass `budget` bytes (it keeps what is left; the
 /// first range moves whatever its size, so none keeps the page closed), the
-/// copies into `encoder` and, in the section arena, the ranges' flat draw ids
-/// (`flat`) along. False when the other pages have no room left.
+/// copies into `encoder` and, in the section arena, the ranges' flat draw ids and
+/// GPU list rows (`ids`) along. False when the other pages have no room left.
+/// The flat draws and GPU lists that name a mesh's range, with what writes to them.
+type MeshIds<'a> = (
+    Option<&'a mut flat::Flat>,
+    Option<&'a mut gpu_lists::GpuLists>,
+    &'a wgpu::Device,
+    &'a mut upload::Uploads,
+);
 fn move_off_page<'a>(
     arena: &mut arena::Arena,
     encoder: &mut wgpu::CommandEncoder,
-    mut flat: Option<(&mut flat::Flat, &wgpu::Device, &mut upload::Uploads)>,
+    mut ids: Option<MeshIds<'_>>,
     meshes: impl Iterator<Item = &'a mut SectionGpu>,
     page: u32,
     part: Part,
@@ -472,9 +484,14 @@ fn move_off_page<'a>(
         };
         arena.copy(encoder, (page, start), to, vertices);
         arena.release(page, start, vertices);
-        if let (Some((flat, device, uploads)), Some(id)) = (&mut flat, s.flat_id) {
-            flat.remove(id);
-            s.flat_id = Some(flat.add(device, encoder, uploads, to.0, to.1, vertices));
+        if let Some((flat, lists, device, uploads)) = &mut ids {
+            if let (Some(flat), Some(id)) = (flat, s.flat_id) {
+                flat.remove(id);
+                s.flat_id = Some(flat.add(device, encoder, uploads, to.0, to.1, vertices));
+            }
+            if let (Some(lists), Some(id)) = (lists, s.list_id) {
+                lists.set(device, encoder, uploads, id, to.1 as u32, &s.sides);
+            }
         }
         part.set(s, to);
         *budget = budget.saturating_sub(bytes);
@@ -742,7 +759,8 @@ pub struct Renderer {
     /// (F3+4 shows it).
     pub lightmap_pixels: [u8; 16 * 16 * 4],
     /// Time the last `render` spent blocked on the GPU or the display
-    /// (acquiring, presenting, offscreen pacing), excluded from CPU time.
+    /// (acquiring, presenting, offscreen pacing, the submit thread holding the queue),
+    /// excluded from CPU time.
     pub last_wait: std::time::Duration,
     /// CPU time of the last `render`, waits excluded.
     pub last_encode: std::time::Duration,
@@ -753,6 +771,9 @@ pub struct Renderer {
     display_fresh: bool,
     window: Arc<Window>,
     pub device: wgpu::Device,
+    /// The shader modules, layouts and pipelines kept for the next renderer on
+    /// this device ([`reuse`]).
+    reuse: Arc<reuse::Reuse>,
     /// Frames are finished and submitted on its submit thread ([`submit`]).
     pub queue: submit::Queue,
     /// The last frame went to the submit thread; whether it had no window surface.
@@ -771,6 +792,8 @@ pub struct Renderer {
     flat: Option<flat::Flat>,
     /// `flat` draws this frame's sections (off: the per-section draws).
     flat_on: bool,
+    /// Phase 1's solid lists made on the GPU, in flat frames (with `flat`).
+    gpu_lists: Option<gpu_lists::GpuLists>,
     /// Occlusion culling of solid section draws, where the GPU's instance
     /// counts reach a multi-draw's entries (Vulkan, Metal).
     cull: Option<cull::Cull>,
@@ -924,6 +947,8 @@ pub struct Renderer {
     /// last asked (`take_dropped_sections`).
     sections_dropped: bool,
     sorted_indices: arena::Arena,
+    /// Buffers of released arena pages, freed a few frames later on a thread of their own.
+    graveyard: arena::Graveyard<wgpu::Buffer>,
     translucent_sorter: translucency::Sorter,
     translucency_cursor: usize,
     /// `DrawIndexedIndirectArgs` for this frame's solid then translucent draws.
@@ -1103,7 +1128,7 @@ const SPRITE_ARRAYS: u32 = 8;
 /// array. wgpu's OpenGL backend picks a texture's target from its layer
 /// count when it is created: one layer makes a 2D texture and a multiple of
 /// six a cube map, neither of which can be viewed as an array.
-fn array_layers(count: u32, gl: bool) -> u32 {
+pub(crate) fn array_layers(count: u32, gl: bool) -> u32 {
     match count {
         _ if !gl => count,
         0 | 1 => 2,
@@ -1857,7 +1882,10 @@ impl Renderer {
                     device_lost: renderer.device_lost.clone(),
                 }
             }
-            None => open_device(&window, offscreen, api, layers).await?,
+            None => {
+                let _step = crate::spans::startup::step("renderer.open_device");
+                open_device(&window, offscreen, api, layers).await?
+            }
         };
         // Computed once: the sprite arrays, the shaders' constants and the
         // shader pack atlas all cut the sprites by it.
@@ -1937,8 +1965,15 @@ impl Renderer {
         if previous.is_none() {
             startup_step(format_args!("creating the pipelines"));
         }
+        // A renderer on the same device takes the previous one's shader
+        // modules, layouts and pipelines where they come out the same.
+        let reuse = previous.map_or_else(Default::default, |r| r.reuse.clone());
+        let generation = reuse.begin();
+        let kept = reuse.on(&device);
+        let pipelines_step = crate::spans::startup::step("renderer.pipelines_textures");
+        let terrain_step = crate::spans::startup::step("renderer.terrain_pipelines");
         let gpu_timer = timing::GpuTimer::new(&device, &queue);
-        let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
+        let shader = kept.create_shader_module(wgpu::ShaderModuleDescriptor {
             label: Some("Horizon terrain"),
             source: wgpu::ShaderSource::Wgsl(include_str!("terrain.wgsl").into()),
         });
@@ -1962,7 +1997,7 @@ impl Renderer {
             ("SPRITE_ARRAYS", f64::from(sprite_arrays)),
             ("SPRITE_SPLIT", f64::from(split)),
         ];
-        let bindings = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+        let bindings = kept.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
             label: Some("Horizon terrain bindings"),
             entries: &[
                 entry(
@@ -2020,7 +2055,7 @@ impl Renderer {
                 ),
             ],
         });
-        let layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
+        let layout = kept.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
             label: Some("Horizon terrain layout"),
             bind_group_layouts: &[Some(&bindings)],
             ..Default::default()
@@ -2056,7 +2091,7 @@ impl Renderer {
                            depth_write: bool,
                            depth_test: bool,
                            blend: Option<wgpu::BlendState>| {
-            device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+            kept.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
                 label: Some(label),
                 layout: Some(layout),
                 vertex: wgpu::VertexState {
@@ -2204,7 +2239,7 @@ impl Renderer {
             false,
             Some(alpha_blend),
         );
-        let depth_reset = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+        let depth_reset = kept.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
             label: Some("Hand depth reset"),
             layout: Some(&layout),
             vertex: wgpu::VertexState {
@@ -2283,6 +2318,7 @@ impl Renderer {
             false,
             Some(alpha_blend),
         );
+        drop(terrain_step);
         let globals = device.create_buffer(&wgpu::BufferDescriptor {
             label: Some("Horizon globals"),
             size: std::mem::size_of::<Globals>() as u64,
@@ -2594,11 +2630,12 @@ impl Renderer {
             &glint_sampler,
         )?;
         hud.atlas_texture = Some(atlas.clone());
-        let entity_shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
+        let entity_step = crate::spans::startup::step("renderer.entity_pipelines");
+        let entity_shader = kept.create_shader_module(wgpu::ShaderModuleDescriptor {
             label: Some("Horizon entities"),
             source: wgpu::ShaderSource::Wgsl(entity_shader().into()),
         });
-        let entity_bindings = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+        let entity_bindings = kept.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
             label: Some("Entity bindings"),
             entries: &[
                 entry(
@@ -2749,12 +2786,12 @@ impl Renderer {
                 },
             ],
         });
-        let entity_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
+        let entity_layout = kept.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
             label: Some("Entity layout"),
             bind_group_layouts: &[Some(&entity_bindings)],
             ..Default::default()
         });
-        let cloud_bindings = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+        let cloud_bindings = kept.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
             label: Some("Cloud bindings"),
             entries: &[entry(
                 0,
@@ -2780,7 +2817,7 @@ impl Renderer {
                 resource: cloud_uniform.as_entire_binding(),
             }],
         });
-        let cloud_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
+        let cloud_layout = kept.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
             label: Some("Cloud layout"),
             bind_group_layouts: &[Some(&entity_bindings), Some(&cloud_bindings)],
             ..Default::default()
@@ -2807,7 +2844,7 @@ impl Renderer {
                                     clouds,
                                     fragment: &str,
                                     write_mask| {
-            device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+            kept.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
                 label: Some(label),
                 layout: Some(if clouds {
                     &cloud_layout
@@ -3069,10 +3106,10 @@ impl Renderer {
             multiview_mask: None,
             cache: None,
         };
-        let additive_pipeline = device.create_render_pipeline(&additive_descriptor);
+        let additive_pipeline = kept.create_render_pipeline(&additive_descriptor);
         // `RenderPipelines.DRAGON_RAYS` uses DepthStencilState.DEFAULT:
         // unlike eyes, a ray hides the faces and rays behind it.
-        let dragon_rays_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+        let dragon_rays_pipeline = kept.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
             label: Some("Dragon death rays"),
             primitive: wgpu::PrimitiveState {
                 cull_mode: Some(wgpu::Face::Back),
@@ -3092,7 +3129,7 @@ impl Renderer {
             write_mask: wgpu::ColorWrites::ALPHA,
         })];
         let hdr_mark_lightning_pipeline =
-            device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+            kept.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
                 label: Some("HDR lightning mark"),
                 vertex: wgpu::VertexState {
                     entry_point: Some("vs_lightning"),
@@ -3107,7 +3144,7 @@ impl Renderer {
                 }),
                 ..additive_descriptor.clone()
             });
-        let lightning_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+        let lightning_pipeline = kept.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
             label: Some("Lightning"),
             vertex: wgpu::VertexState {
                 entry_point: Some("vs_lightning"),
@@ -3116,7 +3153,7 @@ impl Renderer {
             },
             ..additive_descriptor
         });
-        let celestial_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+        let celestial_pipeline = kept.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
             label: Some("Celestial bodies"),
             layout: Some(&entity_layout),
             vertex: wgpu::VertexState {
@@ -3165,6 +3202,7 @@ impl Renderer {
             multiview_mask: None,
             cache: None,
         });
+        drop(entity_step);
         // WorldBorderRenderer: misc/forcefield.png as a MipmappedTexture
         // (repeat, linear minification with mipmaps, nearest magnification).
         let forcefield_size = forcefield.1;
@@ -3210,7 +3248,7 @@ impl Renderer {
             usage: wgpu::BufferUsages::VERTEX | wgpu::BufferUsages::COPY_DST,
             mapped_at_creation: false,
         });
-        let border_bindings = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+        let border_bindings = kept.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
             label: Some("World border bindings"),
             entries: &[
                 entry(
@@ -3269,19 +3307,19 @@ impl Renderer {
                 },
             ],
         });
-        let border_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
+        let border_layout = kept.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
             label: Some("World border layout"),
             bind_group_layouts: &[Some(&border_bindings)],
             ..Default::default()
         });
-        let border_shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
+        let border_shader = kept.create_shader_module(wgpu::ShaderModuleDescriptor {
             label: Some("Horizon world border"),
             source: wgpu::ShaderSource::Wgsl(include_str!("border.wgsl").into()),
         });
         let border_attributes = wgpu::vertex_attr_array![0=>Float32x3,1=>Float32x2];
         // RenderPipelines.WORLD_BORDER: BlendFunction.OVERLAY, no culling,
         // depth writes with a polygon offset of 3 towards the camera.
-        let border_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+        let border_pipeline = kept.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
             label: Some("World border"),
             layout: Some(&border_layout),
             vertex: wgpu::VertexState {
@@ -3334,7 +3372,7 @@ impl Renderer {
             multiview_mask: None,
             cache: None,
         });
-        let screen_shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
+        let screen_shader = kept.create_shader_module(wgpu::ShaderModuleDescriptor {
             label: Some("Horizon screen effects"),
             source: wgpu::ShaderSource::Wgsl(include_str!("screen.wgsl").into()),
         });
@@ -3373,7 +3411,7 @@ impl Renderer {
                 constants: &constants,
                 ..Default::default()
             };
-            device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+            kept.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
                 label: Some("Screen effects"),
                 layout: Some(&entity_layout),
                 vertex: wgpu::VertexState {
@@ -3476,6 +3514,7 @@ impl Renderer {
                 .get_downlevel_capabilities()
                 .flags
                 .contains(wgpu::DownlevelFlags::INDIRECT_EXECUTION);
+        let gpu_lists = flat.as_ref().map(|_| gpu_lists::GpuLists::new(&device));
         let batchable = translucent_batchable(
             &adapter.get_info(),
             multi_draw,
@@ -3542,6 +3581,14 @@ impl Renderer {
         );
         let panorama =
             panorama::Panorama::new(&device, config.format.remove_srgb_suffix(), panorama_faces);
+        drop(pipelines_step);
+        reuse.finish(generation);
+        if previous.is_some() {
+            log::info!(
+                "Horizon renderer: rebuilt on the same device ({} shader modules, layouts and pipelines kept)",
+                reuse.len()
+            );
+        }
         if previous.is_none() {
             startup_step(format_args!(
                 "pipelines ready (multi-draw {}, occlusion culling {}, GPU timer {})",
@@ -3572,6 +3619,7 @@ impl Renderer {
             last_encode: std::time::Duration::ZERO,
             window,
             device,
+            reuse,
             queue: submit::Queue::new(queue, submit::wanted()),
             deferred: None,
             device_lost,
@@ -3581,6 +3629,7 @@ impl Renderer {
             solid_cutout,
             translucent,
             flat_on: flat.is_some(),
+            gpu_lists,
             cull_on: cull.is_some(),
             sides_on: true,
             cull,
@@ -3686,6 +3735,7 @@ impl Renderer {
             translucent_batching,
             sections_dropped: false,
             sorted_indices,
+            graveyard: Default::default(),
             translucent_sorter: translucency::Sorter::default(),
             translucency_cursor: 0,
             indirect,
@@ -3979,6 +4029,10 @@ impl Renderer {
     pub fn section_count(&self) -> usize {
         self.sections.len()
     }
+    /// The running native pack's `[[particle_lights]]`.
+    pub fn particle_lights(&self) -> Option<&[horizon_shader_api::manifest::ParticleLight]> {
+        self.native.as_ref().map(|n| n.particle_lights.as_slice())
+    }
     /// Whether one of Horizon's own packs with `[shadow]` draws, whose shadow pass takes the
     /// frame's `shadow_only` quads.
     pub fn native_shadow(&self) -> bool {
@@ -4122,6 +4176,11 @@ impl Renderer {
         } else {
             None
         };
+        let sides = if mesh.sides.quads() == solid {
+            mesh.sides
+        } else {
+            Sides::unsorted(solid)
+        };
         // Flat draws name the blocks of its range in `arena`: split, its solid
         // quads alone (no frame draws flat then: `translucent_split`).
         let flat_id = self.flat.as_mut().filter(|_| main > 0).map(|f| {
@@ -4134,6 +4193,15 @@ impl Renderer {
                 main,
             )
         });
+        let list_id = self.gpu_lists.as_mut().filter(|_| main > 0).map(|l| {
+            l.add(
+                &self.device,
+                encoder,
+                &mut self.section_uploads,
+                start as u32,
+                &sides,
+            )
+        });
         let stride = std::mem::size_of::<TerrainVertex>() as u64;
         let translucent_arena = self.translucent_arena.as_ref().unwrap_or(&self.arena);
         for (part, arena, (part_page, first)) in [
@@ -4164,11 +4232,7 @@ impl Renderer {
             start,
             translucent_at,
             solid,
-            sides: if mesh.sides.quads() == solid {
-                mesh.sides
-            } else {
-                Sides::unsorted(solid)
-            },
+            sides,
             translucent,
             sort: translucency::SortState::new(
                 mesh.translucent
@@ -4180,6 +4244,7 @@ impl Renderer {
             ),
             sorted_indices,
             flat_id,
+            list_id,
             fading: None,
             leaving: None,
             animated_layers,
@@ -4252,6 +4317,9 @@ impl Renderer {
         if let (Some(flat), Some(id)) = (&mut self.flat, s.flat_id) {
             flat.remove(id);
         }
+        if let (Some(lists), Some(id)) = (&mut self.gpu_lists, s.list_id) {
+            lists.remove(id);
+        }
         if let Some((page, start)) = s.sorted_indices {
             self.sorted_indices
                 .release(page, start, u64::from(s.translucent) * 6);
@@ -4294,13 +4362,15 @@ impl Renderer {
             .sections
             .values_mut()
             .chain(self.lods.values_mut().flat_map(|tile| tile.meshes_mut()));
-        let flat = self
-            .flat
-            .as_mut()
-            .map(|f| (f, &self.device, &mut self.section_uploads));
+        let ids = Some((
+            self.flat.as_mut(),
+            self.gpu_lists.as_mut(),
+            &self.device,
+            &mut self.section_uploads,
+        ));
         let split = self.translucent_arena.is_some();
         let (arena, part) = (&mut self.arena, Part::Section { split });
-        if !move_off_page(arena, encoder, flat, meshes, page, part, &mut budget) {
+        if !move_off_page(arena, encoder, ids, meshes, page, part, &mut budget) {
             // The other pages have no room after all.
             arena.reopen();
         }
@@ -4434,14 +4504,15 @@ impl Renderer {
         self.lod_pending = None;
         self.detail_columns.clear();
         self.detail_revision += 1;
-        self.arena.clear();
+        // A dimension change drops every page at once: freed later, off this thread.
+        self.graveyard.add(self.arena.clear());
         if let Some(arena) = &mut self.translucent_arena {
-            arena.clear();
+            self.graveyard.add(arena.clear());
         }
         if let Some(flat) = &mut self.flat {
             flat.clear();
         }
-        self.sorted_indices.clear();
+        self.graveyard.add(self.sorted_indices.clear());
         self.translucency_cursor = 0;
         if layout == self.layout {
             self.occlusion.clear();
@@ -4605,6 +4676,11 @@ impl Renderer {
                 flat.remove(id);
             }
         }
+        if let Some(lists) = &mut self.gpu_lists {
+            for id in released.iter().filter_map(|s| s.list_id) {
+                lists.remove(id);
+            }
+        }
         self.sorted_indices
             .release_all(released.iter().filter_map(|s| {
                 let (page, start) = s.sorted_indices?;
@@ -4852,6 +4928,11 @@ impl Renderer {
             let world = pack_post::World {
                 atlas: self.pack_atlas.as_ref().map(|a| (a.view.clone(), a.size())),
                 lightmap: self.lightmap_view.clone(),
+                gui_size: self
+                    .hud
+                    .atlas_texture
+                    .as_ref()
+                    .map_or([1, 1], |t| [t.width(), t.height()]),
                 terrain: self.pack_atlas.as_ref().map(|_| pack_post::Geometry {
                     buffers: if flat { &buffers[..1] } else { &buffers },
                     table: self.flat.as_ref().filter(|_| flat).map(|f| &f.draw_layout),
@@ -5324,7 +5405,13 @@ impl Renderer {
     }
     /// `checks`: the error scopes of a scaled screenshot's frame, checked before its PNG is written.
     fn draw_frame(&mut self, frame: &Frame, checks: Option<GpuChecks>) -> Result<bool> {
+        // Its steps as spans (HORIZON_SPIKES): each lap names the step that just ended.
+        let mut laps = crate::spans::laps();
+        let landing = Instant::now();
         self.land_frame();
+        // Waiting for the previous frame (offscreen: at most two on the GPU), not work.
+        let landed = landing.elapsed();
+        self.queue.take_waited();
         // World frames alone follow the shader pack: the game loads the picked one
         // before it draws one. Title frames draw no terrain and keep the layout
         // through a pack dropped (Shader Options) or not loaded yet (`Renderer::new`),
@@ -5332,12 +5419,14 @@ impl Renderer {
         if !frame.title {
             self.follow_translucent_layout();
         }
-        self.arena.trim();
+        let released = self.arena.trim();
+        self.graveyard.add(released);
         let left = self.compact_arena();
         if let Some(arena) = &mut self.translucent_arena {
-            arena.trim();
+            self.graveyard.add(arena.trim());
         }
-        self.sorted_indices.trim();
+        self.graveyard.add(self.sorted_indices.trim());
+        arena::free_later(self.graveyard.advance());
         self.shrink_translucent(left);
         if let Some(flat) = &mut self.flat {
             flat.trim(|page| self.arena.has_page(page));
@@ -5373,6 +5462,7 @@ impl Renderer {
             }
             self.surface_unconfigured = false;
         }
+        laps.lap("r_prepare");
         // Frame generation: its present thread acquires and presents, this frame draws
         // into frames of its own. Not over menus that blur the frame, a shader pack's
         // own post passes, HDR or the title screen.
@@ -5388,6 +5478,8 @@ impl Renderer {
         if !fg {
             self.frame_gen.stop();
         }
+        // Waits for the submit thread since the last frame's present (this frame's uploads).
+        let queued = self.queue.take_waited();
         let acquire = Instant::now();
         let fg_frames = fg
             .then(|| {
@@ -5409,7 +5501,9 @@ impl Renderer {
         } else {
             self.surface.as_ref().map(|s| s.get_current_texture())
         };
-        self.last_wait = acquire.elapsed();
+        self.last_wait = landed + queued + acquire.elapsed();
+        // Inside the acquire's time already.
+        self.queue.take_waited();
         let (surface_frame, reconfigure) = match acquired {
             None => (None, false),
             Some(wgpu::CurrentSurfaceTexture::Success(f)) => (Some(f), false),
@@ -5495,6 +5589,7 @@ impl Renderer {
         let views = self.views(frame);
         let pose = frame.bob * frame.spin;
         let view_proj = views.primary().view_proj(pose);
+        laps.lap("r_acquire");
         // TAA runs where the world post pass does, not under a shader pack's own.
         let taa = !frame.title
             && self.pack_post.as_ref().is_none_or(|p| p.1.is_none())
@@ -5634,9 +5729,21 @@ impl Renderer {
                 0.0,
             ],
             hdr_windows: self.hdr.as_ref().map_or([[0.0; 4]; 2], hdr::Hdr::windows),
+            hdr_light: [
+                frame.sky.sky_light_factor,
+                // The underwater overlay: the sky and fog are the water's own colour there.
+                if frame.screen.iter().any(|q| q.world_tint) {
+                    0.0
+                } else {
+                    frame.sky.sky_light_factor
+                },
+                0.0,
+                0.0,
+            ],
         };
         self.uploads
             .buffer(&mut encoder, &self.globals, 0, bytemuck::bytes_of(&globals));
+        laps.lap("r_targets");
         // GameRenderer.render3dHud: the hand's projection at hudFov, with the
         // bob in its pose rather than the projection (same product).
         let hand_projection = Mat4::from_cols_array(&crate::camera::hand_projection(
@@ -5842,6 +5949,7 @@ impl Renderer {
         }
         self.origins.clear();
         let (sections, retiring) = (&self.sections, &self.lod_retiring);
+        laps.lap("r_cameras");
         // `LevelRenderer.extractSectionDrawGroups`: each section's `getVisibility`. Once
         // nothing is fading (the usual frame), every section is whole without a lookup.
         let fade_ms = fade_millis(frame.chunk_fade);
@@ -5931,10 +6039,40 @@ impl Renderer {
                 (true, true) => &[(1, Quads::All)],
             }
         };
+        // Phase 1's sections can leave finding their facing quads to the GPU
+        // (`gpu_lists`) in frames drawn flat with nothing but the camera's
+        // terrain: no mirror, shader pack terrain or shadow, nor tiles.
+        let use_lists = gpu_lists_on()
+            && !pack_terrain
+            && shadow_view.is_none()
+            && mirror.is_none()
+            && visible_lods.is_empty()
+            && self.flat_on
+            && (self.flat.as_ref()).is_some_and(|f| self.drawn_sections >= f.min_sections);
+        if let Some(lists) = &mut self.gpu_lists {
+            lists.clear(&self.device);
+        }
+        let mut lists = self.gpu_lists.as_mut().filter(|_| use_lists);
         let mut opaque_draws = 0;
         for (i, v) in visible.iter().enumerate() {
             let s = self.sections.get(v.slot);
             let first_phase = cull.as_ref().is_none_or(|c| c.first(v.slot));
+            if first_phase
+                && let (Some(lists), Some(id)) = (&mut lists, s.list_id)
+                && lists.list(
+                    id,
+                    s.page,
+                    v.distance,
+                    &s.sides,
+                    parts(fade_code(s, &v.key) != 0),
+                    v.origin,
+                )
+            {
+                if let Some(c) = &mut cull {
+                    c.drawn(i, v.slot, s.sides.quads() * 6);
+                }
+                continue;
+            }
             let (draws, pages) = if first_phase {
                 (&mut self.draws, &mut self.draw_pages)
             } else {
@@ -6023,6 +6161,7 @@ impl Renderer {
         self.draw_pages.extend_from_slice(&self.phase2_pages);
         let culling = cull.is_some();
         let solid_draws = self.draws.len() as u32;
+        laps.lap("r_section_groups");
         // LevelRenderer: nearby sections each frame, plus a rotating eighth
         // (at least 15) of the visible list. Cached views avoid needless sorts.
         self.translucent_draws.clear();
@@ -6220,6 +6359,7 @@ impl Renderer {
             (shadow_first + shadow_solid) as usize,
         );
         let shadow_translucent = self.draws.len() as u32 - shadow_first - shadow_solid;
+        laps.lap("r_nearby");
         // Metal replays a multi-draw as one draw call per entry.
         self.section_draw_calls = if self.multi_draw && self.info.backend != wgpu::Backend::Metal {
             (0..self.section_draws)
@@ -6305,12 +6445,19 @@ impl Renderer {
                 &self.queue,
                 frame.entities,
                 frame.entity_spans,
+                frame.crumbling_sprite,
                 &mut self.pack_entity_rest,
             );
             entities = &self.pack_entity_rest;
         }
         // GameRenderer.useImprovedTransparency. A shader pack keeps its own
         // path.
+        let hdr_lighting = self.native.is_none()
+            && self.pack_post.as_ref().is_none_or(|p| p.1.is_none())
+            && std::env::var_os("HORIZON_HDR_LIGHTING").is_none_or(|v| v != "0");
+        if let Some(hdr) = &mut self.hdr {
+            hdr.lighting = hdr_lighting;
+        }
         let oit_on = self.improved_transparency
             && !frame.title
             && self.pack_post.as_ref().is_none_or(|p| p.1.is_none())
@@ -6346,6 +6493,7 @@ impl Renderer {
             + translucent_particle_quads
             + translucent_item_quads
             + oit_entity_quads;
+        laps.lap("r_draw_lists");
         // Where the tail of materials the classic and the improved passes
         // both draw ends: the shadows, particles and items count back from it.
         let base_quads = world_quads - oit_entity_quads;
@@ -6491,6 +6639,7 @@ impl Renderer {
                 bytemuck::bytes_of(&uniform),
             );
         }
+        laps.lap("r_materials");
         // Every upload before the frame's first pass: a pass ends wgpu-core's
         // command buffer, so copies between passes would need one more.
         if !frame.screen.is_empty() {
@@ -6533,7 +6682,8 @@ impl Renderer {
         let flat_frame = match &mut self.flat {
             Some(flat)
                 if self.flat_on
-                    && !self.draws.is_empty()
+                    && (!self.draws.is_empty()
+                        || self.gpu_lists.as_ref().is_some_and(|l| l.listed() > 0))
                     && (self.drawn_sections >= flat.min_sections
                         || pack_terrain
                         || shadow_view.is_some()) =>
@@ -6572,6 +6722,8 @@ impl Renderer {
                                 Some((id, lod::instance(v.origin, v.fade)))
                             })),
                         |page| sorted.buffer(page).clone(),
+                        self.gpu_lists.as_mut().filter(|l| l.listed() > 0),
+                        eye.map(|e| e.to_array()),
                         self.own_timing.as_mut(),
                     )
                 })
@@ -6579,7 +6731,8 @@ impl Renderer {
             _ => false,
         };
         if flat_frame {
-            self.section_draw_calls = self.flat.as_ref().map_or(0, |f| f.shadow_calls[0]);
+            self.section_draw_calls = self.flat.as_ref().map_or(0, |f| f.shadow_calls[0])
+                + self.gpu_lists.as_ref().map_or(0, |l| l.calls().len());
         } else if self.multi_draw && !self.draws.is_empty() {
             if self.draws.len() as u64 > self.indirect_capacity {
                 self.indirect_capacity = (self.draws.len() as u64).next_power_of_two();
@@ -6617,6 +6770,7 @@ impl Renderer {
                 .flatten();
         }
         let pack_reads_world = pack_post || native_post;
+        laps.lap("r_uploads");
         // Phase 2 of occlusion culling draws over the depth, and a shader pack or TAA reads it.
         let keep_depth = pack_reads_world
             || (taa && self.world_post.taa)
@@ -6748,6 +6902,7 @@ impl Renderer {
             }
         };
         let sky_visible = sky_open(frame);
+        laps.lap("r_world_pass");
         // One of Horizon's own packs: this frame's inputs; in a timed frame its sky draws in a
         // pass of its own, so that it has a time of its own.
         let mut native_sky_pass = false;
@@ -6886,6 +7041,7 @@ impl Renderer {
             pass.set_bind_group(0, &self.group, &[]);
             sky.draw(&mut pass, &native.frame);
         }
+        laps.lap("r_pack_inputs");
         // The water mirror, for one of Horizon's own packs that reads it: the world as a
         // camera mirrored about the water plane sees it, into a half-resolution target the
         // material stage samples as `reflection`.
@@ -7023,6 +7179,7 @@ impl Renderer {
             };
             native.frame.fit_surface(&self.device, size);
         }
+        laps.lap("r_mirror");
         // One of Horizon's own packs with a material stage: terrain draws with its pipelines,
         // which read the pack's frame at group 3.
         let material = self
@@ -7176,19 +7333,26 @@ impl Renderer {
                     // Without a pack, on Metal, the opaque pass, then the cutout one
                     // (terrain.wgsl's `opaque_quad`), each over phase 1's lists with
                     // quads for it, and over all of phase 2's.
+                    // Each pass's GPU-made lists by group, too (`flat::Flat::list`).
                     let [opaque, cutout] = flat.pass_calls;
-                    let passes: &[(&wgpu::RenderPipeline, std::ops::Range<usize>)] = match pack_flat
-                    {
-                        Some(p) => &[(&p.0, 0..flat.phase1_calls)],
+                    type Passes<'p> =
+                        &'p [(&'p wgpu::RenderPipeline, std::ops::Range<usize>, &'p [u8])];
+                    let passes: Passes = match pack_flat {
+                        Some(p) => &[(&p.0, 0..flat.phase1_calls, &[0, 1])],
                         None if split_solid => &[
-                            (&flat.solid_opaque, 0..opaque),
-                            (&flat.solid_cutout, cutout..flat.phase1_calls),
+                            (&flat.solid_opaque, 0..opaque, &[0]),
+                            (&flat.solid_cutout, cutout..flat.phase1_calls, &[1]),
                         ],
-                        None => &[(&flat.solid, 0..flat.phase1_calls)],
+                        None => &[(&flat.solid, 0..flat.phase1_calls, &[0, 1])],
                     };
                     let draw = |pass: &mut wgpu::RenderPass<'_>| {
-                        for (pipeline, calls) in passes {
+                        for (pipeline, calls, groups) in passes {
                             pass.set_pipeline(pipeline);
+                            if let Some(lists) = &self.gpu_lists {
+                                for &group in *groups {
+                                    flat.draw_lists(pass, lists, group, vertices);
+                                }
+                            }
                             flat.draw(pass, &flat.calls[calls.clone()], vertices);
                         }
                     };
@@ -7218,7 +7382,7 @@ impl Renderer {
                             };
                             pass.set_bind_group(0, &self.group, &[]);
                             pack_frame(&mut pass);
-                            for (pipeline, _) in passes {
+                            for (pipeline, ..) in passes {
                                 pass.set_pipeline(pipeline);
                                 flat.draw_phase2(&mut pass, vertices);
                             }
@@ -8013,6 +8177,7 @@ impl Renderer {
                 (&view_target, self.config.format.remove_srgb_suffix()),
             );
         }
+        laps.lap("r_passes");
         // Under `HORIZON_FRAMEGEN_DEBUG=generated` a screenshot is the made frame.
         let shown_texture = match &fg_frames {
             Some((_, generated)) if fg_made && frame_gen::generated_only() => generated,
@@ -8080,6 +8245,8 @@ impl Renderer {
             match self.queue.submit_later(job) {
                 Ok(()) => {
                     self.deferred = Some(offscreen);
+                    // The frame's waits for the previous one on the submit thread.
+                    self.last_wait += self.queue.take_waited();
                     self.last_encode = started.elapsed().saturating_sub(self.last_wait);
                     self.visible = visible;
                     self.visible_lods = visible_lods;
@@ -8144,6 +8311,8 @@ impl Renderer {
                 );
             }
         }
+        // The frame's own waits for the submit thread (its queue writes and passes).
+        self.last_wait += self.queue.take_waited();
         let present = Instant::now();
         if let Some(surface_frame) = surface_frame {
             // On Wayland this ties RedrawRequested to the compositor's frame
@@ -8176,6 +8345,8 @@ impl Renderer {
             }
         }
         self.last_wait += present.elapsed();
+        // Inside the present's time already.
+        self.queue.take_waited();
         self.last_encode = started.elapsed().saturating_sub(self.last_wait);
         let _ = self.started;
         self.visible = visible;
@@ -8863,6 +9034,12 @@ fn projection_center(view_proj: Mat4) -> Option<Vec3> {
 fn facing_runs(sides: &Sides, eye: Option<Vec3>, origin: [f32; 3], draw: impl FnMut(u32, u32)) {
     facing_runs_from(sides, eye, None, origin, Quads::All, draw)
 }
+/// Whether phase 1's solid lists may be made on the GPU (`flat::Flat::list`);
+/// `HORIZON_GPU_LISTS=0` keeps them on the CPU.
+fn gpu_lists_on() -> bool {
+    static ON: std::sync::OnceLock<bool> = std::sync::OnceLock::new();
+    *ON.get_or_init(|| std::env::var("HORIZON_GPU_LISTS").as_deref() != Ok("0"))
+}
 /// `facing_runs` for the eye and, with `low`, every eye straight below it down to that
 /// camera-relative height (the water mirror's eye).
 fn facing_runs_from(
@@ -9055,6 +9232,14 @@ mod tests {
         assert!(!drawable_size(984, u32::MAX, 32768));
     }
 
+    #[test]
+    fn a_reported_black_level_rounds_down() {
+        use super::hundredths_of_a_nit as h;
+        assert_eq!(h(0.005), 0);
+        assert_eq!(h(0.05), 5);
+        assert_eq!(h(5.0), 100);
+        assert_eq!(h(f32::NAN), 0);
+    }
     #[test]
     fn os_luminances_become_auto_values() {
         use super::os_reported;
@@ -9072,14 +9257,16 @@ mod tests {
             os_reported(&info(Some(998.4), Some(240.0))),
             Some(Reported {
                 paper_white: 240,
-                peak: 998
+                peak: 998,
+                black: 0
             })
         );
         assert_eq!(
             os_reported(&info(Some(120.0), Some(1000.0))),
             Some(Reported {
                 paper_white: 480,
-                peak: 480
+                peak: 480,
+                black: 0
             })
         );
         // White above the calibrated peak (a Samsung QD-OLED's 380, the slider at 456).
@@ -9087,7 +9274,8 @@ mod tests {
             os_reported(&info(Some(380.0), Some(456.0))),
             Some(Reported {
                 paper_white: 456,
-                peak: 456
+                peak: 456,
+                black: 0
             })
         );
         assert_eq!(os_reported(&info(Some(1000.0), None)), None);
@@ -9870,6 +10058,15 @@ fn flush_display_log() {
         (log.last, log.at) = (line, Some(now));
     }
 }
+/// A reported black level, within the setting's range. Rounded down: OLEDs report a figure
+/// just above 0, like KWin's 0.005, which isn't worth lifting the shadows for.
+fn hundredths_of_a_nit(nits: f32) -> u32 {
+    if nits.is_finite() && nits > 0.0 {
+        ((nits * 100.0) as u32).min(100)
+    } else {
+        0
+    }
+}
 fn log_os_reported(reported: Option<crate::graphics::Reported>) {
     log_display(match reported {
         Some(r) => format!(
@@ -9892,6 +10089,7 @@ fn os_reported(info: &wgpu::DisplayHdrInfo) -> Option<crate::graphics::Reported>
     let paper_white = (white.round() as u32).clamp(80, 480);
     Some(crate::graphics::Reported {
         paper_white,
+        black: hundredths_of_a_nit(luminance.min_nits.unwrap_or(0.0)),
         // Windows' SDR brightness slider can set white above the reported peak (480 against
         // a calibrated 380): the highlights then stay at white instead of dropping below it.
         peak: (peak.round() as u32).clamp(200, 10_000).max(paper_white),
@@ -9917,5 +10115,6 @@ fn reported(l: horizon_hdr::wayland::Luminances) -> crate::graphics::Reported {
     crate::graphics::Reported {
         paper_white: 203,
         peak: peak.clamp(200, 10_000),
+        black: hundredths_of_a_nit(l.target_min * 203.0 / l.reference.max(1.0)),
     }
 }

crates/horizon-client-render/src/gfx/arena.rs

@@ -4,7 +4,7 @@
 //! with pages up to `LARGE_PAGE_BYTES`, and their sorted indices too
 //! (`Arena::translucent_indices`): their back-to-front list then stays in one
 //! page of each and draws in a few multi-draws.
-use std::collections::BTreeMap;
+use std::collections::{BTreeMap, VecDeque};
 
 /// Ranges are rounded up to this many vertices to limit fragmentation, and
 /// start at multiples of it (`flat` names sections by these blocks).
@@ -545,14 +545,17 @@ impl Arena {
         old.free.give(previous, capacity - previous);
         true
     }
-    /// Reclaim after an upload batch, so replacing a section can reuse its range.
-    pub fn trim(&mut self) {
+    /// Reclaim after an upload batch, so replacing a section can reuse its range. Gives back
+    /// the buffers of the pages it emptied, for a [`Graveyard`].
+    pub fn trim(&mut self) -> Vec<wgpu::Buffer> {
+        let mut released = Vec::new();
         for page in &mut self.pages {
-            if let Some(p) = page
-                && p.free.0.len() == 1
-                && p.free.0.get(&0) == Some(&p.capacity)
+            if page
+                .as_ref()
+                .is_some_and(|p| p.free.0.len() == 1 && p.free.0.get(&0) == Some(&p.capacity))
+                && let Some(p) = page.take()
             {
-                *page = None;
+                released.push(p.buffer);
             }
         }
         if self.closing.is_some_and(|page| !self.has_page(page)) {
@@ -562,13 +565,67 @@ impl Arena {
         while self.pages.last().is_some_and(Option::is_none) {
             self.pages.pop();
         }
+        released
     }
-    pub fn clear(&mut self) {
-        self.pages.clear();
+    /// Drops every page; gives back their buffers, for a [`Graveyard`].
+    pub fn clear(&mut self) -> Vec<wgpu::Buffer> {
         self.closing = None;
+        self.pages.drain(..).flatten().map(|p| p.buffer).collect()
     }
 }
 
+/// Frames a released page waits before it is freed: by then the GPU is done with the frames that
+/// used it, and the bind groups naming it (flat draws' page tables) are gone, so the freeing
+/// thread holds its last reference.
+const GRAVE_FRAMES: usize = 4;
+
+/// Buffers of released pages, freed [`GRAVE_FRAMES`] frames later on a thread of their own
+/// ([`free_later`]): giving a page of up to 256 MB back to the driver on the render thread took
+/// that frame 8-14 ms of CPU (Mesa's lavapipe), when flight or a teleport emptied a page.
+pub struct Graveyard<T> {
+    graves: VecDeque<Vec<T>>,
+}
+
+impl<T> Default for Graveyard<T> {
+    fn default() -> Self {
+        Self {
+            graves: VecDeque::new(),
+        }
+    }
+}
+
+impl<T> Graveyard<T> {
+    /// Released this frame.
+    pub fn add(&mut self, items: impl IntoIterator<Item = T>) {
+        if self.graves.is_empty() {
+            self.graves.push_back(Vec::new());
+        }
+        if let Some(grave) = self.graves.back_mut() {
+            grave.extend(items);
+        }
+    }
+    /// A frame went by: what was released `GRAVE_FRAMES` frames ago, to free.
+    pub fn advance(&mut self) -> Vec<T> {
+        self.graves.push_back(Vec::new());
+        if self.graves.len() > GRAVE_FRAMES {
+            self.graves.pop_front().unwrap_or_default()
+        } else {
+            Vec::new()
+        }
+    }
+}
+
+/// Drops `items` on a short-lived thread of its own, as `chunk::free_columns` does for
+/// unloaded chunks; should the thread not start, they drop here.
+pub fn free_later<T: Send + 'static>(items: Vec<T>) {
+    if items.is_empty() {
+        return;
+    }
+    let _ = std::thread::Builder::new()
+        .name("Buffer freeing".into())
+        .spawn(move || drop(items));
+}
+
 /// `create_buffer` with an out-of-memory failure returned instead of raised
 /// (raised errors are fatal).
 fn try_create(device: &wgpu::Device, size: u64, usage: wgpu::BufferUsages) -> Option<wgpu::Buffer> {
@@ -587,6 +644,24 @@ fn try_create(device: &wgpu::Device, size: u64, usage: wgpu::BufferUsages) -> Op
 mod tests {
     use super::*;
 
+    /// A released page is handed back for freeing `GRAVE_FRAMES` frames later, in order.
+    #[test]
+    fn graveyard_frees_after_its_frames() {
+        let mut graves = Graveyard::default();
+        graves.add([1, 2]);
+        let mut freed = Vec::new();
+        for frame in 0..GRAVE_FRAMES + 2 {
+            if frame == 1 {
+                graves.add([3]);
+            }
+            freed.push(graves.advance());
+        }
+        let mut expected = vec![Vec::new(); GRAVE_FRAMES + 2];
+        expected[GRAVE_FRAMES - 1] = vec![1, 2];
+        expected[GRAVE_FRAMES] = vec![3];
+        assert_eq!(freed, expected);
+    }
+
     fn device() -> Option<(wgpu::Device, wgpu::Queue)> {
         device_with(wgpu::Features::empty())
     }
@@ -761,6 +836,7 @@ mod tests {
             sort: super::super::translucency::SortState::new(Vec::new()),
             sorted_indices: None,
             flat_id: None,
+            list_id: None,
             fading: None,
             leaving: None,
             animated_layers: Box::new([]),
@@ -1044,6 +1120,7 @@ mod tests {
                 sort: super::super::translucency::SortState::new(Vec::new()),
                 sorted_indices: (translucent > 0).then_some(if indices { at } else { (7, 7) }),
                 flat_id: None,
+                list_id: None,
                 fading: None,
                 leaving: None,
                 animated_layers: Box::new([]),

crates/horizon-client-render/src/gfx/flat.rs

@@ -223,6 +223,7 @@ fn buffer(
 /// from `shadow[0]` (solid) and `shadow[1]` (translucent) on are a shader
 /// pack's shadow camera's, with calls of their own. Phase 1's draws before
 /// `passes[0]` and from `passes[1]` on, the two solid passes' on Metal, too.
+/// The list starts at index `base` (the GPU-made lists' rooms come first: `gpu_lists`).
 #[allow(clippy::too_many_arguments)]
 fn plan(
     draws: &[[u32; 5]],
@@ -235,6 +236,7 @@ fn plan(
     calls: &mut Vec<Call>,
     ranges: &mut Vec<Range>,
     segments: &mut Vec<(Source, u64, u64)>,
+    base: u64,
 ) -> Plan {
     calls.clear();
     ranges.clear();
@@ -242,7 +244,7 @@ fn plan(
     let (mut phase1_calls, mut solid_calls) = (None, None);
     let mut shadow_calls = [None; 2];
     let mut pass_calls = [None; 2];
-    let mut total = 0u64;
+    let mut total = base;
     let mut by_source: Vec<(Source, Vec<Range>)> = Vec::new();
     for (i, (d, &(page, sorted))) in draws.iter().zip(pages).enumerate() {
         if i == phase1_draws {
@@ -540,6 +542,8 @@ impl Flat {
         phase2: Option<&wgpu::Buffer>,
         origins: impl Iterator<Item = (u32, [f32; 4])>,
         sorted_page: impl Fn(u32) -> wgpu::Buffer,
+        mut lists: Option<&mut super::gpu_lists::GpuLists>,
+        eye: Option<[f32; 3]>,
         timing: Option<&mut super::pack_timing::PassTiming>,
     ) -> bool {
         self.phase2_group = None;
@@ -577,6 +581,8 @@ impl Flat {
                 bytemuck::cast_slice(&self.origin_data),
             );
         }
+        // The GPU-made lists' rooms come first in the index list.
+        let room = lists.as_mut().map_or(0, |l| l.rooms());
         let Plan {
             phase1_calls,
             solid_calls,
@@ -594,6 +600,7 @@ impl Flat {
             &mut self.calls,
             &mut self.range_data,
             &mut self.segments,
+            room,
         );
         self.phase1_calls = phase1_calls;
         self.solid_calls = solid_calls;
@@ -656,6 +663,9 @@ impl Flat {
                 bytemuck::cast_slice(&self.phase2_call_data),
             );
         }
+        if let Some(lists) = &mut lists {
+            lists.prepare(device, encoder, uploads, &self.indices, eye);
+        }
         let ranges_at = |first: u64, count: u64| {
             wgpu::BindingResource::Buffer(wgpu::BufferBinding {
                 buffer: &self.ranges,
@@ -725,13 +735,17 @@ impl Flat {
             label: Some("Flatten section draws"),
             timestamp_writes: timing.and_then(|t| t.compute_writes("Flatten")),
         });
+        if let Some(lists) = &lists {
+            lists.dispatch(&mut pass);
+        }
         pass.set_pipeline(&self.flatten);
         for (group, count) in &groups {
             pass.set_bind_group(0, group, &[]);
             pass.dispatch_workgroups((*count).min(GROUP_LIMIT), count.div_ceil(GROUP_LIMIT), 1);
         }
         drop(pass);
-        for page in self.calls.iter().map(|c| c.page) {
+        let list_pages = lists.iter().flat_map(|l| l.calls().iter().map(|c| c.page));
+        for page in self.calls.iter().map(|c| c.page).chain(list_pages) {
             let table = self.pages[page as usize]
                 .as_mut()
                 .expect("a drawn page has its block table");
@@ -772,6 +786,27 @@ impl Flat {
         pass.dispatch_workgroups((*count).min(GROUP_LIMIT), count.div_ceil(GROUP_LIMIT), 1);
     }
 
+    /// Draws pass `group`'s calls of `lists` (`gpu_lists::Out::Indices`, prepared with
+    /// this frame's `prepare`) with a flat pipeline set.
+    pub fn draw_lists<'a>(
+        &self,
+        pass: &mut wgpu::RenderPass<'_>,
+        lists: &super::gpu_lists::GpuLists,
+        group: u8,
+        vertices: impl Fn(u32) -> &'a wgpu::Buffer,
+    ) {
+        if !lists.prepared() {
+            return;
+        }
+        pass.set_index_buffer(self.indices.slice(..), wgpu::IndexFormat::Uint32);
+        for (k, call) in lists.calls().iter().enumerate() {
+            if call.group == group {
+                self.bind_page(pass, call.page, &vertices);
+                lists.draw_indexed(pass, k);
+            }
+        }
+    }
+
     /// The camera's translucent calls.
     pub fn translucent_calls(&self) -> &[Call] {
         &self.calls[self.solid_calls..self.shadow_calls[0]]
@@ -897,6 +932,7 @@ mod tests {
             &mut calls,
             &mut ranges,
             &mut segments,
+            0,
         );
         assert_eq!(total, 6 * 13);
         assert_eq!(phase1_calls, solid_calls);
@@ -945,6 +981,7 @@ mod tests {
             &mut calls,
             &mut ranges,
             &mut segments,
+            0,
         );
         assert_eq!((plan.pass_calls, plan.solid_calls), ([3, 1], 4));
         let call = |page, first, count| Call { page, first, count };
@@ -980,6 +1017,7 @@ mod tests {
             &mut calls,
             &mut ranges,
             &mut segments,
+            0,
         );
         assert_eq!((plan.solid_calls, plan.shadow_calls), (3, [4, 5]));
         let call = |page, first, count| Call { page, first, count };
@@ -1008,6 +1046,7 @@ mod tests {
             &mut calls,
             &mut ranges,
             &mut segments,
+            0,
         );
         assert_eq!(
             plan,
@@ -1125,6 +1164,7 @@ mod tests {
                 &mut calls,
                 &mut ranges,
                 &mut segments,
+                0,
             );
             // Phase 2's draws as the test leaves them: instance counts of 0,
             // 1 where it saw the section.

crates/horizon-client-render/src/gfx/gpu_lists.rs

@@ -0,0 +1,639 @@
+//! Phase 1's solid section draws made on the GPU (gpu_lists.wgsl).
+//!
+//! Each frame the render thread walked every section phase 1 draws through
+//! `mesher::Sides::visible_from` to find the runs of its quads that face the eye,
+//! and pushed one draw per run. Here it pushes one record per section instead:
+//! its row (where its quads start and how `Sides` sorted them, uploaded with its
+//! mesh), the call each of its parts draws in and its camera-relative origin. The
+//! GPU finds the same runs and writes their indices, per call (one per pass
+//! group and arena page), into the flat draws' index list, drawn with
+//! `draw_indexed_indirect`. Calls take room for all the quads of their sections'
+//! parts; the GPU counts the indices it wrote.
+//!
+//! Solid draws write depth and are tested against it, so their order within a
+//! call does not change the picture.
+use crate::mesher::{Part, Sides};
+
+/// Words per row: first vertex, `Sides::gpu_row`, padding.
+const ROW: usize = 24;
+/// Most workgroups along one dimension of a dispatch.
+const GROUP_LIMIT: u32 = 65535;
+
+/// A part of a section in a record: `Part` as gpu_lists.wgsl names it.
+fn part_code(part: Part) -> u32 {
+    match part {
+        Part::All => 0,
+        Part::Opaque => 1,
+        Part::Cutout => 2,
+    }
+}
+
+/// One of the frame's calls: what pass `group` draws of arena `page`, from
+/// index `first` with room for `count`.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(super) struct ListCall {
+    pub group: u8,
+    pub page: u32,
+    pub first: u32,
+    pub count: u32,
+}
+
+pub(super) struct GpuLists {
+    pipeline: wgpu::ComputePipeline,
+    layout: wgpu::BindGroupLayout,
+    /// Per id: its first vertex and `Sides::gpu_row` (`ROW` words).
+    rows: wgpu::Buffer,
+    row_capacity: u64,
+    free_ids: Vec<u32>,
+    next_id: u32,
+    /// The frame's sections: id, the call and part of each of its parts, its
+    /// number of parts; then its origin.
+    records: Vec<[u32; 8]>,
+    record_buffer: wgpu::Buffer,
+    record_capacity: u64,
+    calls: Vec<ListCall>,
+    /// `calls`' index by page and group in the band of distance the last
+    /// section listed is in (`u32::MAX`: none yet).
+    call_of: Vec<u32>,
+    band: u32,
+    call_data: Vec<[u32; 5]>,
+    /// Per call `DrawIndexedIndirectArgs`; the GPU adds what it writes to the count.
+    call_buffer: wgpu::Buffer,
+    call_capacity: u64,
+    view: wgpu::Buffer,
+    group: Option<(wgpu::BindGroup, u32)>,
+    /// The indices the frame's calls take, and the most they may.
+    room: u64,
+    cap: u64,
+}
+
+fn buffer(
+    device: &wgpu::Device,
+    label: &str,
+    size: u64,
+    usage: wgpu::BufferUsages,
+) -> wgpu::Buffer {
+    device.create_buffer(&wgpu::BufferDescriptor {
+        label: Some(label),
+        size,
+        // COPY_SRC: rows move to a larger buffer; tests read calls back.
+        usage: usage | wgpu::BufferUsages::COPY_DST | wgpu::BufferUsages::COPY_SRC,
+        mapped_at_creation: false,
+    })
+}
+
+fn entry(binding: u32, ty: wgpu::BufferBindingType) -> wgpu::BindGroupLayoutEntry {
+    wgpu::BindGroupLayoutEntry {
+        binding,
+        visibility: wgpu::ShaderStages::COMPUTE,
+        ty: wgpu::BindingType::Buffer {
+            ty,
+            has_dynamic_offset: false,
+            min_binding_size: None,
+        },
+        count: None,
+    }
+}
+
+impl GpuLists {
+    pub fn new(device: &wgpu::Device) -> Self {
+        let read = wgpu::BufferBindingType::Storage { read_only: true };
+        let write = wgpu::BufferBindingType::Storage { read_only: false };
+        let layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+            label: Some("Section lists"),
+            entries: &[
+                entry(0, read),
+                entry(1, read),
+                entry(2, wgpu::BufferBindingType::Uniform),
+                entry(3, write),
+                entry(4, write),
+            ],
+        });
+        let module = device.create_shader_module(wgpu::ShaderModuleDescriptor {
+            label: Some("Section lists"),
+            source: wgpu::ShaderSource::Wgsl(include_str!("gpu_lists.wgsl").into()),
+        });
+        let pipeline = device.create_compute_pipeline(&wgpu::ComputePipelineDescriptor {
+            label: Some("Section lists"),
+            layout: Some(
+                &device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
+                    label: Some("Section lists"),
+                    bind_group_layouts: &[Some(&layout)],
+                    ..Default::default()
+                }),
+            ),
+            module: &module,
+            entry_point: Some("flatten_sides"),
+            compilation_options: Default::default(),
+            cache: None,
+        });
+        let storage = wgpu::BufferUsages::STORAGE;
+        let indirect = wgpu::BufferUsages::INDIRECT | storage;
+        Self {
+            pipeline,
+            layout,
+            rows: buffer(device, "Section rows", ROW as u64 * 4, storage),
+            row_capacity: 1,
+            free_ids: Vec::new(),
+            next_id: 0,
+            records: Vec::new(),
+            record_buffer: buffer(device, "Sections listed", 32, storage),
+            record_capacity: 1,
+            calls: Vec::new(),
+            call_of: Vec::new(),
+            band: 0,
+            call_data: Vec::new(),
+            call_buffer: buffer(device, "Section list calls", 20, indirect),
+            call_capacity: 1,
+            view: buffer(
+                device,
+                "Section lists' eye",
+                16,
+                wgpu::BufferUsages::UNIFORM,
+            ),
+            group: None,
+            room: 0,
+            cap: 0,
+        }
+    }
+
+    /// A mesh uploaded from vertex `start` of its page, its solid quads sorted as
+    /// `sides` says: its id, whose row is written through `uploads` in `encoder`.
+    pub fn add(
+        &mut self,
+        device: &wgpu::Device,
+        encoder: &mut wgpu::CommandEncoder,
+        uploads: &mut super::upload::Uploads,
+        start: u32,
+        sides: &Sides,
+    ) -> u32 {
+        let id = self.free_ids.pop().unwrap_or_else(|| {
+            self.next_id += 1;
+            self.next_id - 1
+        });
+        self.set(device, encoder, uploads, id, start, sides);
+        id
+    }
+
+    pub fn remove(&mut self, id: u32) {
+        self.free_ids.push(id);
+    }
+
+    /// Mesh `id` now starts at vertex `start` (moved to another page).
+    pub fn set(
+        &mut self,
+        device: &wgpu::Device,
+        encoder: &mut wgpu::CommandEncoder,
+        uploads: &mut super::upload::Uploads,
+        id: u32,
+        start: u32,
+        sides: &Sides,
+    ) {
+        let need = u64::from(id) + 1;
+        if need > self.row_capacity {
+            let capacity = need.next_power_of_two().max(1024);
+            let rows = buffer(
+                device,
+                "Section rows",
+                capacity * ROW as u64 * 4,
+                wgpu::BufferUsages::STORAGE,
+            );
+            // Earlier rows: uploads record their copies in `encoder`, so this one follows them.
+            encoder.copy_buffer_to_buffer(
+                &self.rows,
+                0,
+                &rows,
+                0,
+                self.row_capacity * ROW as u64 * 4,
+            );
+            self.rows = rows;
+            self.row_capacity = capacity;
+        }
+        let mut row = [0u32; ROW];
+        row[0] = start;
+        row[1..23].copy_from_slice(&sides.gpu_row());
+        uploads.buffer(
+            encoder,
+            &self.rows,
+            u64::from(id) * ROW as u64 * 4,
+            bytemuck::cast_slice(&row),
+        );
+    }
+
+    /// Starts the frame's lists.
+    pub fn clear(&mut self, device: &wgpu::Device) {
+        self.records.clear();
+        self.calls.clear();
+        self.call_of.fill(u32::MAX);
+        self.band = 0;
+        self.room = 0;
+        self.group = None;
+        // A quarter of the binding they share with the CPU's draws.
+        self.cap = device.limits().max_storage_buffer_binding_size / 16;
+    }
+
+    /// Section `id`, in `page`, at `origin` from the camera and `distance`
+    /// (squared, as bits) from it: each of `parts` (pass group, part) draws the
+    /// quads of the part that face the eye. False, listing nothing, when the
+    /// frame's lists hold all the room they may: the caller draws it.
+    ///
+    /// Sections come nearest first. Each band of distance gets calls of its own,
+    /// drawn in that order, as the CPU's lists keep them (`page_runs`): within
+    /// a call the GPU writes sections in no set order, and cutout quads, which
+    /// tile GPUs can't hide before shading, then draw mostly front to back.
+    pub fn list(
+        &mut self,
+        id: u32,
+        page: u32,
+        distance: u64,
+        sides: &Sides,
+        parts: &[(u8, Part)],
+        origin: [f32; 3],
+    ) -> bool {
+        let parts = &parts[..parts.len().min(2)];
+        let mut counts = [0; 2];
+        for (count, &(_, part)) in counts.iter_mut().zip(parts) {
+            *count = sides.part_quads(part) * 6;
+        }
+        let room = u64::from(counts[0]) + u64::from(counts[1]);
+        if self.room + room > self.cap {
+            return false;
+        }
+        self.room += room;
+        let band = super::page_runs::band(distance) as u32;
+        if band != self.band {
+            self.band = band;
+            self.call_of.fill(u32::MAX);
+        }
+        let mut record = [id, 0, 0, parts.len() as u32, 0, 0, 0, 0];
+        for (k, &(group, part)) in parts.iter().enumerate() {
+            let key = page as usize * 2 + usize::from(group.min(1));
+            if self.call_of.len() <= key {
+                self.call_of.resize(key + 1, u32::MAX);
+            }
+            if self.call_of[key] == u32::MAX {
+                self.call_of[key] = self.calls.len() as u32;
+                self.calls.push(ListCall {
+                    group,
+                    page,
+                    first: 0,
+                    count: 0,
+                });
+            }
+            let call = self.call_of[key];
+            self.calls[call as usize].count += counts[k];
+            record[1 + k] = call | part_code(part) << 28;
+        }
+        for (to, o) in record[4..7].iter_mut().zip(origin) {
+            *to = o.to_bits();
+        }
+        self.records.push(record);
+        true
+    }
+
+    /// The sections listed this frame.
+    pub fn listed(&self) -> usize {
+        self.records.len()
+    }
+
+    /// The frame's calls, with their rooms once laid out (`rooms`).
+    pub fn calls(&self) -> &[ListCall] {
+        &self.calls
+    }
+
+    /// Lays the calls' rooms out one after the other from the start of the
+    /// index list: the indices they take.
+    pub fn rooms(&mut self) -> u64 {
+        let mut room = 0u64;
+        for call in &mut self.calls {
+            call.first = room as u32;
+            room += u64::from(call.count);
+        }
+        room
+    }
+
+    /// Stages the frame's sections, calls and eye (camera-relative; none: every
+    /// quad faces it), and binds them for `dispatch` writing into `indices`.
+    /// After `rooms`.
+    pub fn prepare(
+        &mut self,
+        device: &wgpu::Device,
+        encoder: &mut wgpu::CommandEncoder,
+        uploads: &mut super::upload::Uploads,
+        indices: &wgpu::Buffer,
+        eye: Option<[f32; 3]>,
+    ) {
+        self.group = None;
+        let records = self.records.len() as u64;
+        if records == 0 {
+            return;
+        }
+        if records > self.record_capacity {
+            self.record_capacity = records.next_power_of_two();
+            self.record_buffer = buffer(
+                device,
+                "Sections listed",
+                self.record_capacity * 32,
+                wgpu::BufferUsages::STORAGE,
+            );
+        }
+        uploads.buffer(
+            encoder,
+            &self.record_buffer,
+            0,
+            bytemuck::cast_slice(&self.records),
+        );
+        self.call_data.clear();
+        self.call_data
+            .extend(self.calls.iter().map(|c| [0, 1, c.first, 0, 0]));
+        let calls = self.call_data.len() as u64;
+        let indirect = wgpu::BufferUsages::INDIRECT | wgpu::BufferUsages::STORAGE;
+        if calls > self.call_capacity {
+            self.call_capacity = calls.next_power_of_two();
+            self.call_buffer = buffer(
+                device,
+                "Section list calls",
+                self.call_capacity * 20,
+                indirect,
+            );
+        }
+        uploads.buffer(
+            encoder,
+            &self.call_buffer,
+            0,
+            bytemuck::cast_slice(&self.call_data),
+        );
+        let [x, y, z] = eye.unwrap_or_default();
+        let view = [x, y, z, if eye.is_some() { 1.0 } else { 0.0 }];
+        uploads.buffer(encoder, &self.view, 0, bytemuck::cast_slice(&view));
+        let group = device.create_bind_group(&wgpu::BindGroupDescriptor {
+            label: Some("Section lists"),
+            layout: &self.layout,
+            entries: &[
+                wgpu::BindGroupEntry {
+                    binding: 0,
+                    resource: wgpu::BindingResource::Buffer(wgpu::BufferBinding {
+                        buffer: &self.record_buffer,
+                        offset: 0,
+                        size: wgpu::BufferSize::new(records * 32),
+                    }),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 1,
+                    resource: self.rows.as_entire_binding(),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 2,
+                    resource: self.view.as_entire_binding(),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 3,
+                    resource: self.call_buffer.as_entire_binding(),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 4,
+                    resource: indices.as_entire_binding(),
+                },
+            ],
+        });
+        self.group = Some((group, records as u32));
+    }
+
+    /// Writes the frame's lists (after `prepare`).
+    pub fn dispatch(&self, pass: &mut wgpu::ComputePass<'_>) {
+        let Some((group, records)) = &self.group else {
+            return;
+        };
+        let groups = *records;
+        pass.set_pipeline(&self.pipeline);
+        pass.set_bind_group(0, group, &[]);
+        pass.dispatch_workgroups(groups.min(GROUP_LIMIT), groups.div_ceil(GROUP_LIMIT), 1);
+    }
+
+    /// Whether `dispatch` writes this frame's lists.
+    pub fn prepared(&self) -> bool {
+        self.group.is_some()
+    }
+
+    /// Draws call `k` with a pipeline, its page's vertices and the index list bound.
+    pub fn draw_indexed(&self, pass: &mut wgpu::RenderPass<'_>, k: usize) {
+        pass.draw_indexed_indirect(&self.call_buffer, k as u64 * 20);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::mesher::{Part, Sides};
+    use wgpu::util::DeviceExt;
+
+    struct Section {
+        sides: Sides,
+        origin: [f32; 3],
+        start: u32,
+        page: u32,
+        parts: &'static [(u8, Part)],
+    }
+
+    /// Random sorts: some parts empty, grouped or not, split or not, planes in
+    /// and out of a section, each listed in one of the three ways it can be.
+    fn sections(count: usize) -> Vec<Section> {
+        let mut seed = 0x2545_f491_4f6c_dd1du64;
+        let mut next = |n: u32| {
+            seed = seed
+                .wrapping_mul(6_364_136_223_846_793_005)
+                .wrapping_add(1_442_695_040_888_963_407);
+            ((seed >> 33) % u64::from(n)) as u32
+        };
+        (0..count)
+            .map(|_| {
+                let mut ends = [0; 14];
+                let mut end = 0;
+                for e in &mut ends {
+                    if next(3) > 0 {
+                        end += next(40);
+                    }
+                    *e = end;
+                }
+                let planes = std::array::from_fn(|_| next(17) as f32 + next(16) as f32 / 16.0);
+                Section {
+                    sides: Sides::from_parts(ends, next(2) == 0, next(4) > 0, planes),
+                    origin: [0, 1, 2].map(|_| next(129) as f32 - 64.0),
+                    start: next(10_000) * 4,
+                    page: next(3),
+                    parts: match next(3) {
+                        0 => &[(0, Part::All)],
+                        1 => &[(0, Part::Opaque), (1, Part::Cutout)],
+                        _ => &[(1, Part::All)],
+                    },
+                }
+            })
+            .collect()
+    }
+
+    /// The runs the CPU finds for a section's part, as `Gfx` drew them.
+    fn cpu_runs(s: &Section, part: Part, eye: Option<[f32; 3]>) -> Vec<(u32, u32)> {
+        let mut runs = Vec::new();
+        let draw = |first, quads| runs.push((first, quads));
+        match eye {
+            Some(eye) => {
+                let eye = [0, 1, 2].map(|a| eye[a] - s.origin[a]);
+                s.sides.visible_from(eye, eye[1], part, draw);
+            }
+            None => s.sides.every(part, draw),
+        }
+        runs
+    }
+
+    /// Lists `sections` from each of a few eyes; per eye, the lists, the
+    /// calls' words and the indices written.
+    fn run(sections: &[Section]) -> Option<Vec<(Option<[f32; 3]>, GpuLists, Vec<u32>, Vec<u32>)>> {
+        let (device, queue) = device()?;
+        let mut results = Vec::new();
+        for eye in [
+            Some([3.5f32, 70.25, -12.0]),
+            Some([-40.0, -3.0, 50.5]),
+            None,
+        ] {
+            let mut lists = GpuLists::new(&device);
+            lists.clear(&device);
+            let mut rows = vec![0u32; sections.len() * ROW];
+            for (id, s) in sections.iter().enumerate() {
+                rows[id * ROW] = s.start;
+                rows[id * ROW + 1..id * ROW + 23].copy_from_slice(&s.sides.gpu_row());
+                // Nearest first, over several bands.
+                let distance = (id as f64 * 2.0).powi(2).to_bits();
+                assert!(lists.list(id as u32, s.page, distance, &s.sides, s.parts, s.origin));
+            }
+            let room = lists.rooms();
+            let init = |contents: &[u8], usage| {
+                device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+                    label: None,
+                    contents,
+                    usage,
+                })
+            };
+            let storage = wgpu::BufferUsages::STORAGE | wgpu::BufferUsages::COPY_SRC;
+            lists.rows = init(bytemuck::cast_slice(&rows), storage);
+            let indices = init(&vec![0xffu8; room as usize * 4], storage);
+            let mut encoder = device.create_command_encoder(&Default::default());
+            let mut uploads = super::super::upload::Uploads::new(&device);
+            lists.prepare(&device, &mut encoder, &mut uploads, &indices, eye);
+            uploads.finish(&encoder);
+            {
+                let mut pass = encoder.begin_compute_pass(&Default::default());
+                lists.dispatch(&mut pass);
+            }
+            queue.submit([encoder.finish()]);
+            let read_back = |buffer: &wgpu::Buffer, words: u64| -> Vec<u32> {
+                let read = device.create_buffer(&wgpu::BufferDescriptor {
+                    label: None,
+                    size: words * 4,
+                    usage: wgpu::BufferUsages::MAP_READ | wgpu::BufferUsages::COPY_DST,
+                    mapped_at_creation: false,
+                });
+                let mut encoder = device.create_command_encoder(&Default::default());
+                encoder.copy_buffer_to_buffer(buffer, 0, &read, 0, words * 4);
+                queue.submit([encoder.finish()]);
+                read.slice(..).map_async(wgpu::MapMode::Read, |_| {});
+                device.poll(wgpu::PollType::wait_indefinitely()).unwrap();
+                bytemuck::cast_slice(&read.slice(..).get_mapped_range().unwrap()).to_vec()
+            };
+            let calls = read_back(&lists.call_buffer, lists.calls.len() as u64 * 5);
+            let words = read_back(&indices, room);
+            results.push((eye, lists, calls, words));
+        }
+        Some(results)
+    }
+
+    fn device() -> Option<(wgpu::Device, wgpu::Queue)> {
+        let instance = crate::gfx::test_gpu::instance();
+        let Ok(adapter) = pollster::block_on(instance.request_adapter(&Default::default())) else {
+            eprintln!("no GPU adapter: skipped");
+            return None;
+        };
+        let device = pollster::block_on(adapter.request_device(&Default::default())).ok();
+        if device.is_none() {
+            eprintln!("no GPU device: skipped");
+        }
+        device
+    }
+
+    /// The call section `i`'s `k`th part draws in, as listed.
+    fn call_of(lists: &GpuLists, i: usize, k: usize) -> usize {
+        (lists.records[i][1 + k] & 0x0fff_ffff) as usize
+    }
+
+    /// Each band of distance and page gets a pass's calls of its own, in the
+    /// order sections come (nearest first), and sections of one share them.
+    #[test]
+    fn calls_go_by_band_then_page_nearest_first() {
+        let Some((device, _)) = device() else {
+            return;
+        };
+        let mut lists = GpuLists::new(&device);
+        lists.clear(&device);
+        let sides = Sides::unsorted(4);
+        let parts = &[(0, Part::Opaque), (1, Part::Cutout)];
+        for (page, blocks) in [(1, 10.0), (0, 20.0), (1, 30.0), (1, 100.0), (0, 130.0)] {
+            let distance = f64::powi(blocks, 2).to_bits();
+            assert!(lists.list(0, page, distance, &sides, parts, [0.0; 3]));
+        }
+        let calls: Vec<_> = lists
+            .calls()
+            .iter()
+            .map(|c| (c.group, c.page, c.count))
+            .collect();
+        assert_eq!(
+            calls,
+            [
+                (0, 1, 48),
+                (1, 1, 48),
+                (0, 0, 24),
+                (1, 0, 24),
+                (0, 1, 24),
+                (1, 1, 24),
+                (0, 0, 24),
+                (1, 0, 24)
+            ]
+        );
+    }
+
+    /// `flatten_sides` writes, in each call's room, the indices of exactly the
+    /// runs `Sides::visible_from` finds for each listed section's parts (in
+    /// some order: workgroups take room as they come), and counts them.
+    #[test]
+    fn flatten_sides_writes_the_runs_the_cpu_finds() {
+        let sections = sections(200);
+        let Some(results) = run(&sections) else {
+            return;
+        };
+        for (eye, lists, calls, out) in results {
+            let mut expected = vec![Vec::new(); lists.calls.len()];
+            for (i, s) in sections.iter().enumerate() {
+                for (k, &(_, part)) in s.parts.iter().enumerate() {
+                    let call = call_of(&lists, i, k);
+                    for (first, quads) in cpu_runs(s, part, eye) {
+                        for k in 0..quads * 6 {
+                            let corner = [0, 1, 2, 0, 2, 3][(k % 6) as usize];
+                            expected[call].push(s.start + first * 4 + (k / 6) * 4 + corner);
+                        }
+                    }
+                }
+            }
+            for (k, call) in lists.calls.iter().enumerate() {
+                let count = calls[k * 5] as usize;
+                assert_eq!(
+                    count,
+                    expected[k].len(),
+                    "call {k}'s index count, eye {eye:?}"
+                );
+                assert_eq!(calls[k * 5 + 2], call.first);
+                let mut got = out[call.first as usize..call.first as usize + count].to_vec();
+                got.sort_unstable();
+                expected[k].sort_unstable();
+                assert_eq!(got, expected[k], "call {k}'s indices, eye {eye:?}");
+            }
+        }
+    }
+}

crates/horizon-client-render/src/gfx/gpu_lists.wgsl

@@ -0,0 +1,178 @@
+// Phase 1's solid section draws made on the GPU (gfx/gpu_lists.rs): per section
+// listed, the runs of its quads that face the eye, found as
+// `mesher::Sides::visible_from` finds them on the CPU, written into the call
+// each of its parts draws in (one per pass group and arena page) after taking
+// room there: their indices, in the flat draws' index list, as `flatten_seen`
+// does for occlusion culling's phase 2. Solid draws write depth and are tested
+// against it, so their order within a call does not change the picture.
+struct View {
+    // The eye relative to the camera, and 1.0 when there is one (`sides_on`);
+    // without, every bucket is drawn (`Sides::every`).
+    eye: vec3<f32>,
+    has_eye: f32,
+}
+// Per section listed: its row's id; for each of its parts (up to two) the call
+// it draws in, with the part (`PART_*`) in the top bits; its number of parts.
+// Then its origin relative to the camera.
+struct Record {
+    words: vec4<u32>,
+    origin: vec4<f32>,
+}
+@group(0) @binding(0) var<storage, read> records: array<Record>;
+// Per id, `ROW` words: its first vertex in its page, then `Sides::gpu_row`
+// (14 ends, 7 planes' bits, flags).
+@group(0) @binding(1) var<storage, read> rows: array<u32>;
+@group(0) @binding(2) var<uniform> view: View;
+// Per call `DrawIndexedIndirectArgs`: its index count starts at 0, its first
+// index is where its room starts.
+@group(0) @binding(3) var<storage, read_write> calls: array<atomic<u32>>;
+// The flat draws' index list.
+@group(0) @binding(4) var<storage, read_write> out: array<u32>;
+
+const ROW: u32 = 24u;
+const LANES: u32 = 64u;
+const PART_ALL: u32 = 0u;
+const PART_OPAQUE: u32 = 1u;
+const PART_CUTOUT: u32 = 2u;
+const CALL_MASK: u32 = 0x0fffffffu;
+// `sides::MARGIN`.
+const MARGIN: f32 = 0.0625;
+
+// Index `k` of a solid draw: quad k / 6's vertices 0 1 2 0 2 3.
+fn quad(k: u32) -> u32 {
+    let c = k % 6u;
+    return (k / 6u) * 4u + select(select(c - 2u, 0u, c == 3u), c, c < 3u);
+}
+
+fn plane(row: u32, bucket: u32) -> f32 {
+    return bitcast<f32>(rows[row + 15u + bucket]);
+}
+
+// `Sides::visible_from`'s `seen`, buckets in mesh order: +X, +Z, other, +Y, -Z, -X, -Y.
+fn seen(row: u32, bucket: u32, eye: vec3<f32>) -> bool {
+    var faces = true;
+    if view.has_eye != 0.0 {
+        switch bucket {
+            case 0u: { faces = eye.x > plane(row, 0u) - MARGIN; }
+            case 1u: { faces = eye.z > plane(row, 1u) - MARGIN; }
+            case 3u: { faces = eye.y > plane(row, 3u) - MARGIN; }
+            case 4u: { faces = eye.z < plane(row, 4u) + MARGIN; }
+            case 5u: { faces = eye.x < plane(row, 5u) + MARGIN; }
+            case 6u: { faces = eye.y < plane(row, 6u) + MARGIN; }
+            default: {}
+        }
+    }
+    return faces;
+}
+
+// A part's runs (first quad, quads): at most 7, as a run ends at a part left
+// out and there are 14.
+struct Runs {
+    n: u32,
+    quads: u32,
+    runs: array<vec2<u32>, 7>,
+}
+
+// `Sides::runs` for `part` of the mesh at `row`, seen from `eye` (relative to
+// the section): empty parts do not break a run.
+fn part_runs(row: u32, part: u32, eye: vec3<f32>) -> Runs {
+    var r: Runs;
+    let grouped = (rows[row + 22u] & 1u) != 0u;
+    let split = (rows[row + 22u] & 2u) != 0u;
+    var start = 0u;
+    var open = false;
+    var first = 0u;
+    for (var n = 0u; n < 14u; n++) {
+        let end = rows[row + 1u + n];
+        if end == start {
+            continue;
+        }
+        var bucket: u32;
+        var cutout: bool;
+        if grouped {
+            bucket = n % 7u;
+            cutout = n >= 7u;
+        } else {
+            bucket = n / 2u;
+            cutout = n % 2u == 1u;
+        }
+        let wanted = part == PART_ALL || !split
+            || (part == PART_OPAQUE && !cutout) || (part == PART_CUTOUT && cutout);
+        let take = wanted && seen(row, bucket, eye);
+        if take && !open {
+            open = true;
+            first = start;
+        } else if !take && open {
+            r.runs[r.n] = vec2(first, start - first);
+            r.quads += start - first;
+            r.n++;
+            open = false;
+        }
+        start = end;
+    }
+    if open {
+        r.runs[r.n] = vec2(first, start - first);
+        r.quads += start - first;
+        r.n++;
+    }
+    return r;
+}
+
+fn record_index(group: vec3<u32>) -> u32 {
+    return group.y * 65535u + group.x;
+}
+
+// The eye relative to `record`'s section.
+fn eye_of(record: Record) -> vec3<f32> {
+    return view.eye - record.origin.xyz;
+}
+
+fn part_word(record: Record, p: u32) -> u32 {
+    return select(record.words.z, record.words.y, p == 0u);
+}
+
+// Lane 0's runs per part, and where each part's indices start.
+var<workgroup> found: array<Runs, 2>;
+var<workgroup> at: array<u32, 2>;
+
+// One workgroup per record: lane 0 finds the runs and takes room for their
+// indices, then every lane writes them.
+@compute @workgroup_size(64)
+fn flatten_sides(@builtin(workgroup_id) group: vec3<u32>,
+    @builtin(local_invocation_index) lane: u32) {
+    let r = record_index(group);
+    if r >= arrayLength(&records) {
+        return;
+    }
+    let record = records[r];
+    let row = record.words.x * ROW;
+    let parts = record.words.w;
+    if lane == 0u {
+        let eye = eye_of(record);
+        for (var p = 0u; p < parts; p++) {
+            let word = part_word(record, p);
+            let runs = part_runs(row, word >> 28u, eye);
+            let call = (word & CALL_MASK) * 5u;
+            var begin = 0u;
+            if runs.quads > 0u {
+                begin = atomicLoad(&calls[call + 2u]) + atomicAdd(&calls[call], runs.quads * 6u);
+            }
+            found[p] = runs;
+            at[p] = begin;
+        }
+    }
+    workgroupBarrier();
+    let base = rows[row];
+    for (var p = 0u; p < parts; p++) {
+        var to = at[p];
+        for (var k = 0u; k < found[p].n; k++) {
+            let run = found[p].runs[k];
+            let first = base + run.x * 4u;
+            let count = run.y * 6u;
+            for (var i = lane; i < count; i += LANES) {
+                out[to + i] = first + quad(i);
+            }
+            to += count;
+        }
+    }
+}

crates/horizon-client-render/src/gfx/hdr.rs

@@ -149,6 +149,9 @@ pub struct Hdr {
     pub ui: f32,
     /// Which pixels of a light source shine (`Masks`).
     pub masks: Masks,
+    /// HDR lighting: off while a shader pack's post or material stage runs, the pack's own, and
+    /// with `HORIZON_HDR_LIGHTING=0`, to compare.
+    pub lighting: bool,
     /// Calibration's test picture while it runs.
     pub calibration: Option<Calibration>,
 }
@@ -293,6 +296,7 @@ impl Hdr {
             tiers: TIERS,
             ui: 1.0,
             masks: MASKS,
+            lighting: true,
             calibration: None,
         }
     }
@@ -539,6 +543,11 @@ impl Hdr {
         ]);
         params[5] = self.black.clamp(0.0, paper);
         params[6] = self.ui.clamp(0.25, 1.0);
+        params[7] = if self.lighting {
+            scene_gain(self.peak, self.paper_white)
+        } else {
+            1.0
+        };
         for (i, t) in self.tiers.iter().enumerate() {
             params[8 + i] = t.share;
         }
@@ -618,6 +627,12 @@ fn logo_mask(device: &wgpu::Device, queue: &wgpu::Queue) -> wgpu::TextureView {
         .create_view(&Default::default())
 }
 
+/// What the strongest light multiplies a surface by, in HDR lighting: 4, which looked right
+/// across biomes; less only where there is little headroom to ease into (`hdr.wgsl`).
+fn scene_gain(peak: f32, paper_white: f32) -> f32 {
+    (peak / paper_white.max(1.0) * 1.75).clamp(1.0, 4.0)
+}
+
 #[cfg(test)]
 mod tests {
     use super::{Output, pick};
@@ -670,3 +685,18 @@ mod tests {
         assert_eq!(pick(&caps(&[(F::Bgra8UnormSrgb, S::SRGB)]), None), None);
     }
 }
+
+#[cfg(test)]
+mod lighting_tests {
+    use super::scene_gain;
+
+    #[test]
+    fn the_lighting_scales_with_the_headroom() {
+        // Enough headroom: the full strength, whatever the paper white.
+        assert_eq!(scene_gain(1000.0, 430.0), 4.0);
+        assert_eq!(scene_gain(1060.0, 203.0), 4.0);
+        // Little headroom, and none.
+        assert_eq!(scene_gain(600.0, 400.0), 2.625);
+        assert_eq!(scene_gain(200.0, 480.0), 1.0);
+    }
+}

crates/horizon-client-render/src/gfx/native_material.rs

@@ -39,6 +39,8 @@ struct HorizonMaterialOut {
     @location(8) @interpolate(flat) face: u32,
     @location(9) @interpolate(flat) fluid_quad: u32,
     @location(10) @interpolate(flat) emission: f32,
+    // terrain.wgsl's `emission`, for HDR output's mark.
+    @location(11) @interpolate(flat) hdr_code: u32,
 }
 fn horizon_material_vertex(position: vec3<f32>, uv: vec2<f32>, layer: u32, color: vec4<f32>,
     light: vec2<u32>, origin: vec3<f32>) -> HorizonMaterialOut {
@@ -67,7 +69,9 @@ fn horizon_material_vertex(position: vec3<f32>, uv: vec2<f32>, layer: u32, color
     out.fluid_quad = u32(fluid);
     // The tier (0 none, 1 low, 2 incandescent, 3 bright, 4 very bright) as how strongly the
     // face shines: a redstone torch 7/15, a torch 14/15, glowstone 1.
-    let tier = 15u - (flags & 15u);
+    out.hdr_code = 15u - (flags & 15u);
+    // Codes above 4 are the same tiers, shining all over rather than in their bright parts.
+    let tier = select(out.hdr_code, out.hdr_code - 4u, out.hdr_code > 4u);
     out.emission = select(min(f32(tier) * 7.0 / 15.0, 1.0), 0.0, tier == 0u);
     return out;
 }
@@ -145,7 +149,8 @@ fn horizon_material_color(in: HorizonMaterialOut, translucent: bool) -> vec4<f32
     return material(MaterialInput(albedo, in.tint, in.light, in.lightmap, in.position, in.uv,
         translucent, horizon_sprite_tags(in.layer & 0x7fffu),
         horizon_sprite_material(in.layer & 0x7fffu), in.clip.xy / frame.resolution,
-        in.face, fluid, in.emission, normal, tangent)).color;
+        in.face, fluid, in.emission, normal, tangent,
+        horizon_terrain_native_colored_light(in.position))).color;
 }
 var<private> horizon_material_face_normal: vec3<f32>;
 struct HorizonMaterialSolid {
@@ -154,15 +159,33 @@ struct HorizonMaterialSolid {
     // stage's `surface_at` compares with the final depth.
     @location(1) surface: vec4<f32>,
 }
+// What `fs_solid` leaves in the frame's alpha for HDR output, from the sprite before the pack's
+// material: the pack decides the colour, Horizon still knows which pixels are light sources.
+fn horizon_material_mark(in: HorizonMaterialOut, texel: vec4<f32>) -> f32 {
+    if in.hdr_code > 0u {
+        let whole = in.hdr_code > 4u;
+        let tier = select(in.hdr_code, in.hdr_code - 4u, whole);
+        let l = in.layer & 0x7fffu;
+        let t = textureLoad(horizon_terrain_emission_thresholds,
+            vec2(i32(l % horizon_terrain_SPRITE_SPLIT), i32(l / horizon_terrain_SPRITE_SPLIT)), 0);
+        let y = horizon_terrain_brightness(texel.rgb);
+        if whole || y >= t.r {
+            return horizon_terrain_hdr_mark(tier, y);
+        }
+    }
+    return 1.0;
+}
 @fragment fn horizon_material_fs_solid(in: HorizonMaterialOut) -> HorizonMaterialSolid {
     let color = horizon_material_color(in, false);
+    let texel = horizon_terrain_sprite(in.uv, in.layer & 0x7fffu);
     // Bit 15 of the layer marks opaque leaves (forceOpaque): no alpha cutout.
     if color.a < 0.5 && (in.layer & 0x8000u) == 0u { discard; }
     if horizon_surface.w == 0.0 {
         set_surface(horizon_material_face_normal, 0.0, 0.0);
     }
     var out: HorizonMaterialSolid;
-    out.color = horizon_material_fogged(vec4(color.rgb, 1.0), in.spherical, in.cylindrical);
+    let mark = horizon_material_mark(in, texel);
+    out.color = horizon_material_fogged(vec4(color.rgb, mark), in.spherical, in.cylindrical);
     out.surface = vec4(horizon_surface.xyz, in.clip.z);
     return out;
 }

crates/horizon-client-render/src/gfx/native_pack.rs

@@ -21,6 +21,8 @@ pub struct NativePack {
     pub weather: Option<wgpu::RenderPipeline>,
     /// The draw of the shadow map the stages read, if the pack asks for one.
     pub shadow: Option<NativeShadow>,
+    /// `[[particle_lights]]`.
+    pub particle_lights: Vec<horizon_shader_api::manifest::ParticleLight>,
     /// GPU time of each pass, while the renderer asks for it (`pack_timing.rs`).
     pub timing: Option<PassTiming>,
 }
@@ -133,6 +135,7 @@ impl NativePack {
             labels.extend(post.labels().into_iter().map(str::to_owned));
         }
         let pack = Self {
+            particle_lights: report.manifest.particle_lights.clone(),
             frame,
             sky,
             material,

crates/horizon-client-render/src/gfx/native_render.rs

@@ -6,7 +6,23 @@
 use super::Vertex;
 use super::pack_draw::EntitySpan;
 use glam::{DVec3, Mat4};
-use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{
+    OnceLock,
+    atomic::{AtomicBool, Ordering},
+};
+
+mod generated;
+pub use generated::{RenderHooks, RenderNeedsEvent, WorldDrawnEvent};
+pub use wgpu;
+
+static RENDERERS: OnceLock<Box<[&'static dyn RenderHooks]>> = OnceLock::new();
+
+/// Install trait mod renderers in dispatch order, once per process.
+pub fn install(
+    renderers: Box<[&'static dyn RenderHooks]>,
+) -> Result<(), Box<[&'static dyn RenderHooks]>> {
+    RENDERERS.set(renderers)
+}
 
 static MODS_BUILT_IN: AtomicBool = AtomicBool::new(false);
 
@@ -18,12 +34,16 @@ pub fn set_mods_built_in(on: bool) {
 /// Whether [`native_world_drawn`] may draw ([`set_mods_built_in`]).
 pub fn world_drawn_hooked() -> bool {
     MODS_BUILT_IN.load(Ordering::Relaxed)
+        || RENDERERS
+            .get()
+            .is_some_and(|renderers| !renderers.is_empty())
 }
 
 /// What a mod can draw with once the world is drawn: after the sky, terrain, entities,
 /// particles, weather and the world post pass, before the first-person hand, the HUD and the
 /// screens. `color` holds the world's picture (copy it out before reading it: it is the target
 /// drawn into), `depth` the world's depth, reversed (0 is the sky).
+#[non_exhaustive]
 pub struct WorldDrawn<'a> {
     pub device: &'a wgpu::Device,
     pub queue: &'a wgpu::Queue,
@@ -59,6 +79,7 @@ pub struct WorldDrawn<'a> {
 /// What the mods need from a frame that the game doesn't make for itself. Each mod sets what it
 /// needs and leaves the rest, so several can ask.
 #[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+#[non_exhaustive]
 pub struct RenderNeeds {
     /// Record `Frame::entity_spans` without a shader pack: entity runs get a stable id from
     /// their type's name, block entity runs their block state.
@@ -70,13 +91,13 @@ pub struct RenderNeeds {
 /// The world is drawn (see [`WorldDrawn`]). Not called on the title screen's panorama.
 #[inline(never)]
 pub fn native_world_drawn(world: &mut WorldDrawn<'_>) {
-    let _ = world;
+    generated::dispatch_world_drawn(RENDERERS.get().map_or(&[], |renderers| renderers), world);
 }
 
 /// Asked as a frame is built and drawn: set what your mod needs.
 #[inline(never)]
 pub fn native_render_needs(needs: &mut RenderNeeds) {
-    let _ = needs;
+    generated::dispatch_render_needs(RENDERERS.get().map_or(&[], |renderers| renderers), needs);
 }
 
 /// What the mods need this frame ([`native_render_needs`]).
@@ -85,3 +106,34 @@ pub fn render_needs() -> RenderNeeds {
     native_render_needs(&mut needs);
     needs
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    struct Depth;
+    impl RenderHooks for Depth {
+        fn render_needs(&self, event: &mut RenderNeedsEvent<'_>) {
+            event.needs.world_depth = true;
+        }
+    }
+    struct Spans;
+    impl RenderHooks for Spans {
+        fn render_needs(&self, event: &mut RenderNeedsEvent<'_>) {
+            event.needs.entity_spans = event.needs.world_depth;
+        }
+    }
+
+    #[test]
+    fn needs_accumulate_in_mod_order() {
+        let mut needs = RenderNeeds::default();
+        generated::dispatch_render_needs(&[&Depth, &Spans], &mut needs);
+        assert_eq!(
+            needs,
+            RenderNeeds {
+                world_depth: true,
+                entity_spans: true
+            }
+        );
+    }
+}

crates/horizon-client-render/src/gfx/native_render/generated.rs

@@ -0,0 +1,36 @@
+// @generated by cargo run -p xtask -- mod-api; do not edit.
+use super::*;
+pub trait RenderHooks: Send + Sync {
+    /// The world is drawn (see [`WorldDrawn`]). Not called on the title screen's panorama.
+    fn world_drawn(&self, event: &mut WorldDrawnEvent<'_, '_>) {
+        let _ = event;
+    }
+    /// Asked as a frame is built and drawn: set what your mod needs.
+    ///
+    /// Every mod gets `event.needs` in order and may add, change or remove needs.
+    fn render_needs(&self, event: &mut RenderNeedsEvent<'_>) {
+        let _ = event;
+    }
+}
+/// What [`RenderHooks::world_drawn`] is told. Fields may be added: the struct is `#[non_exhaustive]`.
+#[non_exhaustive]
+pub struct WorldDrawnEvent<'a, 'b> {
+    pub world: &'a mut WorldDrawn<'b>,
+}
+pub fn dispatch_world_drawn(mods: &[&dyn RenderHooks], world: &mut WorldDrawn<'_>) {
+    let mut event = WorldDrawnEvent { world };
+    for mod_hook in mods {
+        mod_hook.world_drawn(&mut event);
+    }
+}
+/// What [`RenderHooks::render_needs`] is told. Fields may be added: the struct is `#[non_exhaustive]`.
+#[non_exhaustive]
+pub struct RenderNeedsEvent<'a> {
+    pub needs: &'a mut RenderNeeds,
+}
+pub fn dispatch_render_needs(mods: &[&dyn RenderHooks], needs: &mut RenderNeeds) {
+    let mut event = RenderNeedsEvent { needs };
+    for mod_hook in mods {
+        mod_hook.render_needs(&mut event);
+    }
+}

crates/horizon-client-render/src/gfx/pack_entities.rs

@@ -319,6 +319,7 @@ impl PackEntities {
         entities: &[Vertex],
         spans: &[EntitySpan],
         drawn: [bool; PROGRAMS],
+        crack: ([f32; 4], [u32; 2]),
         shadow: Casters,
         rest: &mut Vec<Vertex>,
     ) {
@@ -330,7 +331,9 @@ impl PackEntities {
         rest.extend_from_slice(&entities[..first.min(entities.len())]);
         for (span, range) in runs(entities.len(), spans) {
             let run = &entities[range];
-            let program = program_of(&span).filter(|_| plain(run));
+            let program = program_of(&span).filter(|&p| {
+                plain(run) || (p == DESTROY && run.iter().all(|v| matches!(v.layer, 11 | 12)))
+            });
             let pack = program.is_some_and(|p| drawn[p]) && !span.hidden;
             let casts = program.is_some_and(|p| shadow.cast(&span, p));
             if !pack && !span.hidden {
@@ -341,6 +344,9 @@ impl PackEntities {
             };
             let start = self.scratch.len() as u32;
             self.scratch.extend_from_slice(run);
+            if program == DESTROY {
+                project_cracks(&mut self.scratch[start as usize..], crack.0, crack.1);
+            }
             let (entity_id, block_id) = match program {
                 BLOCK => (0, span.id),
                 _ => (span.id, 0),
@@ -419,7 +425,8 @@ pub const ENTITY: usize = 0;
 pub const BLOCK: usize = 1;
 pub const TRANSLUCENT: usize = 2;
 pub const PARTICLE: usize = 3;
-pub const PROGRAMS: usize = 4;
+pub const DESTROY: usize = 4;
+pub const PROGRAMS: usize = 5;
 
 /// Which program draws `span`'s run, given which of them (or their fallbacks) the pack has;
 /// `None`: Horizon draws it.
@@ -440,6 +447,8 @@ pub fn program_of(span: &EntitySpan) -> Option<usize> {
         BLOCK
     } else if span.stage == render_stage("PARTICLES") {
         PARTICLE
+    } else if span.stage == render_stage("DESTROY") {
+        DESTROY
     } else {
         return None;
     })
@@ -461,6 +470,16 @@ pub fn runs(
 mod tests {
     use super::*;
 
+    #[test]
+    fn destroy_stage_uses_the_pack_only_when_a_program_is_available() {
+        let destroy = EntitySpan {
+            stage: render_stage("DESTROY"),
+            ..Default::default()
+        };
+        assert!(drawn_by_pack(&destroy, [true; PROGRAMS]).is_some());
+        assert_eq!(drawn_by_pack(&destroy, [false; PROGRAMS]), None);
+    }
+
     #[test]
     fn runs_split_the_list_between_pack_and_horizon() {
         let v = |layer| Vertex {
@@ -483,15 +502,21 @@ mod tests {
         let all = [true; PROGRAMS];
         assert_eq!(drawn_by_pack(&spans[0], all), Some(ENTITY));
         assert_eq!(drawn_by_pack(&spans[1], all), Some(PARTICLE));
-        assert_eq!(drawn_by_pack(&spans[1], [true, true, true, false]), None);
-        assert_eq!(drawn_by_pack(&spans[2], [true, false, true, true]), None);
+        assert_eq!(
+            drawn_by_pack(&spans[1], [true, true, true, false, true]),
+            None
+        );
+        assert_eq!(
+            drawn_by_pack(&spans[2], [true, false, true, true, true]),
+            None
+        );
         assert_eq!(drawn_by_pack(&spans[2], all), Some(BLOCK));
         let shadow = EntitySpan {
             translucent: true,
             ..spans[0]
         };
         assert_eq!(drawn_by_pack(&shadow, all), Some(TRANSLUCENT));
-        assert_eq!(drawn_by_pack(&span(0, "DESTROY", 0), all), None);
+        assert_eq!(drawn_by_pack(&span(0, "DESTROY", 0), all), Some(DESTROY));
         // A beacon beam's quads stay Horizon's.
         assert!(plain(&[v(0), v(0), v(0), v(0), v(1)]));
         assert!(!plain(&[v(0), v(0), v(0), v(0), v(6)]));
@@ -523,3 +548,53 @@ mod tests {
         assert!(!some.cast(&spans[2], BLOCK) && some.cast(&lit, BLOCK));
     }
 }
+
+/// Decode the destroy-stage origin stored in the light bytes and project one continuous
+/// sprite over each model face. Pack geometry uses ordinary atlas UVs, not Horizon's overlay codes.
+fn project_cracks(vertices: &mut [Vertex], sprite: [f32; 4], atlas: [u32; 2]) {
+    let dims = [atlas[0].max(1) as f32, atlas[1].max(1) as f32];
+    for quad in vertices.as_chunks_mut::<4>().0 {
+        let origin = [
+            (quad[0].light & 65535) as f32 / 65535.0,
+            (quad[0].light >> 16) as f32 / 65535.0,
+        ];
+        let origin = [0, 1].map(|i| (origin[i] * dims[i]).round() / dims[i]);
+        let min = [0, 1]
+            .map(|i| (quad.iter().map(|v| v.uv[i]).fold(f32::INFINITY, f32::min) + 0.0001).floor());
+        for v in quad {
+            v.uv =
+                [0, 1].map(|i| origin[i] + (v.uv[i] - min[i]).clamp(0.001, 0.999) * sprite[i + 2]);
+            v.layer = 0;
+            v.light = 0x0000_f0f0;
+        }
+    }
+}
+
+#[cfg(test)]
+mod crack_projection_tests {
+    use super::*;
+    #[test]
+    fn crack_uvs_keep_a_full_sprite_and_decode_each_stage() {
+        let mut vertices: Vec<Vertex> = [[-1.0, -1.0], [-1.0, 0.0], [0.0, 0.0], [0.0, -1.0]]
+            .into_iter()
+            .map(|uv| Vertex {
+                uv,
+                layer: 11,
+                light: crate::breaking::stage_light([0.25, 0.5]),
+                ..bytemuck::Zeroable::zeroed()
+            })
+            .collect();
+        project_cracks(
+            &mut vertices,
+            [0.0, 0.0, 16.0 / 4096.0, 16.0 / 9216.0],
+            [4096, 9216],
+        );
+        assert!(
+            vertices
+                .iter()
+                .all(|v| v.layer == 0 && v.uv[0] >= 0.25 && v.uv[0] < 0.25 + 16.0 / 4096.0)
+        );
+        assert!((vertices[2].uv[0] - vertices[0].uv[0]) > 15.0 / 4096.0);
+        assert!((vertices[1].uv[1] - vertices[0].uv[1]) > 15.0 / 9216.0);
+    }
+}

crates/horizon-client-render/src/gfx/pack_post.rs

@@ -408,6 +408,7 @@ pub(super) struct World<'a> {
     pub block_ids: &'a [i32],
     /// The atlas of the sun and moon's sprites.
     pub celestial: Option<wgpu::TextureView>,
+    pub gui_size: [u32; 2],
     /// Set 1 of the clouds' draw: their offset and palette.
     pub clouds: Option<&'a wgpu::BindGroupLayout>,
     /// The game can hand its rain and snow to the pack.
@@ -510,6 +511,7 @@ pub struct PackPost {
     /// with the page buffer it was made for.
     block_ids: Option<(wgpu::BindGroupLayout, wgpu::Buffer)>,
     page_groups: HashMap<u32, (wgpu::Buffer, wgpu::BindGroup)>,
+    gui_size: [u32; 2],
     /// GPU time of each pass, while the renderer asks for it (`pack_timing.rs`).
     pub timing: Option<super::pack_timing::PassTiming>,
     /// `depthtex0` at the screen's centre, read back for `centerDepthSmooth`.
@@ -1341,11 +1343,16 @@ fn build_pass(
         } else if let Some(&buffer) = p.buffers.get(l) {
             let format = formats[buffer as usize];
             let mut state = target(format);
-            if let (Some(t), Some(b)) = (&mut state, p.blend)
-                && format
-                    .guaranteed_format_features(features)
-                    .flags
-                    .contains(wgpu::TextureFormatFeatureFlags::BLENDABLE)
+            if let (Some(t), Some(b)) = (
+                &mut state,
+                p.buffer_blends
+                    .iter()
+                    .find(|(n, _)| *n == buffer)
+                    .map_or(p.blend, |(_, b)| *b),
+            ) && format
+                .guaranteed_format_features(features)
+                .flags
+                .contains(wgpu::TextureFormatFeatureFlags::BLENDABLE)
             {
                 t.blend = Some(blend_state(b));
             }
@@ -1433,7 +1440,15 @@ fn build_pass(
                 depth_write_enabled: Some(g.depth_write),
                 depth_compare: Some(wgpu::CompareFunction::LessEqual),
                 stencil: Default::default(),
-                bias: Default::default(),
+                bias: if p.name == "gbuffers_damagedblock" {
+                    wgpu::DepthBiasState {
+                        constant: -10,
+                        slope_scale: -1.0,
+                        clamp: 0.0,
+                    }
+                } else {
+                    Default::default()
+                },
             }),
             multisample: Default::default(),
             fragment: Some(wgpu::FragmentState {
@@ -1893,8 +1908,15 @@ impl PackPost {
             post.block,
             post.entities_translucent,
             post.particles,
+            post.damaged_block,
+        ];
+        let late = [
+            false,
+            false,
+            post.translucent_late,
+            post.particles_late,
+            false,
         ];
-        let late = [false, false, post.translucent_late, post.particles_late];
         let shadow_only = (post.shadow_only_player, post.shadow_only_lit_blocks);
         let shadow_programs = [post.shadow_entities, post.shadow_block];
         let entity_vertices = (programs.iter().chain(&shadow_programs))
@@ -1910,8 +1932,21 @@ impl PackPost {
             cull: false,
         });
         let entity_passes = programs.map(|p| {
-            p.zip(entity_geometry.as_ref())
-                .and_then(|(p, g)| build(p, Some(g)))
+            p.zip(entity_geometry.as_ref()).and_then(|(p, g)| {
+                if p.name == "gbuffers_damagedblock" {
+                    let decal = Geometry {
+                        buffers: g.buffers,
+                        table: g.table,
+                        depth_write: false,
+                        atlas: g.atlas.clone(),
+                        ids: g.ids,
+                        cull: false,
+                    };
+                    build(p, Some(&decal))
+                } else {
+                    build(p, Some(g))
+                }
+            })
         });
         let shadow_entities = shadow_programs.map(|p| {
             p.zip(entity_geometry.as_ref())
@@ -2243,6 +2278,7 @@ impl PackPost {
             draws,
             block_ids,
             page_groups: HashMap::new(),
+            gui_size: world.gui_size,
             timing: None,
             center_depth: None,
             custom,
@@ -2868,6 +2904,7 @@ impl PackPost {
         queue: &wgpu::Queue,
         entities: &[super::Vertex],
         spans: &[super::pack_draw::EntitySpan],
+        crumbling: [f32; 4],
         rest: &mut Vec<super::Vertex>,
     ) {
         let shadow = self.shadow_casters();
@@ -2884,6 +2921,7 @@ impl PackPost {
             entities,
             spans,
             drawn,
+            (crumbling, self.gui_size),
             shadow,
             rest,
         );

crates/horizon-client-render/src/gfx/pack_uniforms.rs

@@ -404,9 +404,9 @@ impl FrameUniforms {
             frame.depth_far,
         );
         let camera = frame.camera.as_vec3();
+        let first_frame = self.previous.is_none();
         let (previous_exact, previous_view, previous_projection) =
-            self.previous
-                .unwrap_or((glam::DVec3::ZERO, Mat4::ZERO, Mat4::ZERO));
+            self.previous.unwrap_or((frame.camera, view, projection));
         let previous_camera = previous_exact.as_vec3();
         self.previous = Some((frame.camera, view, projection));
         // The camera's whole blocks and the rest, exact however far from the origin.
@@ -436,6 +436,10 @@ impl FrameUniforms {
         };
         self.wetness = smooth(self.wetness, inputs.rain, half_life / 20.0, dt);
         let eye = inputs.eye_light.map(|l| (l * 16) as f32);
+        if first_frame {
+            self.wetness = inputs.rain;
+            self.eye_smooth = eye;
+        }
         for (smoothed, target) in self.eye_smooth.iter_mut().zip(eye) {
             *smoothed = smooth(*smoothed, target, 10.0 / 20.0, dt);
         }
@@ -849,3 +853,147 @@ mod tests {
         );
     }
 }
+
+#[cfg(test)]
+mod initial_history_tests {
+    use super::*;
+    use crate::hud::HudBatch;
+    fn float(u: &FrameUniforms, name: &str) -> [f32; 16] {
+        match u.values[index(name).unwrap()] {
+            Value::F(v) => v,
+            _ => panic!("float uniform expected"),
+        }
+    }
+    #[test]
+    fn first_history_is_current_then_tracks_the_actual_previous_frame() {
+        let hud = HudBatch::new([800, 450]);
+        let mut f = frame(&hud);
+        let mut u = FrameUniforms::default();
+        f.camera = DVec3::new(1024.25, -3.5, 11.75);
+        f.yaw = 21.0;
+        f.pitch = -16.0;
+        u.update(&f, &PackInputs::default(), [800, 450]);
+        assert_eq!(
+            float(&u, "previousCameraPosition"),
+            float(&u, "cameraPosition")
+        );
+        for (prior, current) in [
+            ("gbufferPreviousProjection", "gbufferProjection"),
+            ("gbufferPreviousModelView", "gbufferModelView"),
+        ] {
+            assert_eq!(float(&u, prior), float(&u, current));
+            assert!(float(&u, prior).iter().any(|v| *v != 0.0));
+        }
+        let camera = float(&u, "cameraPosition");
+        let view = float(&u, "gbufferModelView");
+        let projection = float(&u, "gbufferProjection");
+        f.camera = DVec3::new(-100.0, 20.0, 40.0);
+        f.yaw = 90.0;
+        f.pitch = 50.0;
+        f.fov_degrees = 100.0;
+        u.update(&f, &PackInputs::default(), [1000, 500]);
+        assert_eq!(float(&u, "previousCameraPosition"), camera);
+        assert_eq!(float(&u, "gbufferPreviousModelView"), view);
+        assert_eq!(float(&u, "gbufferPreviousProjection"), projection);
+        assert_ne!(
+            float(&u, "previousCameraPosition"),
+            float(&u, "cameraPosition")
+        );
+    }
+    #[test]
+    fn environmental_smoothing_starts_at_the_first_inputs_without_resetting_each_frame() {
+        let hud = HudBatch::new([800, 450]);
+        let f = frame(&hud);
+        let mut u = FrameUniforms::default();
+        let mut input = PackInputs {
+            rain: 0.75,
+            eye_light: [3, 14],
+            ..Default::default()
+        };
+        u.update(&f, &input, [800, 450]);
+        assert_eq!(float(&u, "wetness")[0], 0.75);
+        match u.values[index("eyeBrightnessSmooth").unwrap()] {
+            Value::I(v) => assert_eq!(&v[..2], &[48, 224]),
+            _ => panic!("integer uniform expected"),
+        }
+        input.rain = 0.0;
+        input.eye_light = [0, 0];
+        u.update(&f, &input, [800, 450]);
+        assert!(float(&u, "wetness")[0] > 0.0);
+        assert!(u.eye_smooth.iter().all(|v| *v > 0.0));
+    }
+    fn frame(hud: &HudBatch) -> Frame<'_> {
+        Frame {
+            eye: glam::DVec3::ZERO,
+            eye_rotation: [0.0; 2],
+            first_person: true,
+            shadow_scene_revision: (0, 0),
+            shadow_cache: false,
+            water_plane: None,
+            weather: &[],
+            weather_time: crate::weather::Time::new(0, 0.0),
+            camera: glam::DVec3::new(0.5, 100.0, 0.5),
+            yaw: 0.0,
+            pitch: 10.0,
+            fov_degrees: 85.0,
+            bob: glam::Mat4::IDENTITY,
+            spin: glam::Mat4::IDENTITY,
+            sky: crate::environment::Sky::default(),
+            distance: 12.0,
+            detail_distance: 12.0,
+            depth_far: 1000.0,
+            underwater: false,
+            cave_culling: false,
+            title: true,
+            sky_blocked: false,
+            skybox: false,
+            end_sky: false,
+            end_sky_sprite: None,
+            environment_fog: None,
+            water_fog: [0.0; 3],
+            fog: None,
+            dark_disc: false,
+            outline: Vec::new(),
+            outline_after_terrain: false,
+            outline_high_contrast: false,
+            debug_lines: &[],
+            debug_lines_on_top: &[],
+            debug_crosshair: &[],
+            hud,
+            glint_alpha: 0.75,
+            glint_ticks: 0.0,
+            nether_lighting: false,
+            entities: &[],
+            entity_motion: &[],
+            colored_lights: &[],
+            emissive_layers: &[],
+            shadow_only: &[],
+            entity_spans: &[],
+            glowing: &[],
+            dynamic_lights: &[],
+            clouds: None,
+            lightning: Default::default(),
+            additive: &[],
+            see_through: &[],
+            celestial: &[],
+            stars: None,
+            hand: &[],
+            hand_fov_degrees: 70.0,
+            screen: &[],
+            pack: Default::default(),
+            border: None,
+            game_time: 0.0,
+            shader_game_time: 0.0,
+            end_portal_sprites: [[0.0; 4]; 2],
+            crumbling_sprite: [0.0; 4],
+            ticks: 0,
+            darkness: (0.0, 0.0),
+            night_vision: 0.0,
+            block_flicker: 0.0,
+            boss_darken: 0.0,
+            menu_blur: None,
+            chunk_fade: 0.0,
+            post_effects: crate::post_chain::Request::none(),
+        }
+    }
+}

crates/horizon-client-render/src/gfx/page_runs.rs

@@ -29,6 +29,11 @@ pub(super) struct Run {
     pub tag: [u32; 3],
 }
 
+/// The band of a section `distance` from the camera (squared, as bits).
+pub(super) fn band(distance: u64) -> u64 {
+    (f64::from_bits(distance).sqrt() / BAND) as u64
+}
+
 #[derive(Default)]
 pub(super) struct PageRuns {
     runs: Vec<Run>,
@@ -58,7 +63,7 @@ impl PageRuns {
         tag: [u32; 3],
     ) {
         if len > 0 {
-            let band = (f64::from_bits(distance).sqrt() / BAND) as u64;
+            let band = band(distance);
             self.runs.push(Run {
                 key: u64::from(group) << GROUP_SHIFT | band << 32 | u64::from(page),
                 start: start as u32,

crates/horizon-client-render/src/gfx/reuse.rs

@@ -0,0 +1,181 @@
+//! Pipelines kept between the renderers built on one device. The start builds
+//! three (the boot screen's, the title artwork's, the world's) and a resource
+//! reload or a graphics option builds another; each compiled every shader
+//! module and pipeline again, though most come out identical (the boot and
+//! title renderers' entirely, the world's entity pipelines). On a driver that
+//! compiles slowly (a cold shader cache, llvmpipe, a weak CPU) that was seconds
+//! of the main thread before the title showed.
+//!
+//! An object is kept under its descriptor's `Debug` text: wgpu prints the
+//! labels, sources, constants, formats and states, and the handles a descriptor
+//! names (shader modules, layouts) by their ids, so a descriptor that names a
+//! kept handle matches only the same handle. Kept objects stay alive, so their
+//! ids are never reused while they are keys.
+use std::{
+    collections::HashMap,
+    sync::{Mutex, PoisonError},
+};
+
+/// One map of kept objects with the generation each was last asked for in.
+struct Kept<T> {
+    map: Mutex<HashMap<String, (T, u32)>>,
+}
+impl<T> Default for Kept<T> {
+    fn default() -> Self {
+        Self {
+            map: Mutex::new(HashMap::new()),
+        }
+    }
+}
+impl<T: Clone> Kept<T> {
+    /// The object kept under `key`, else `make`'s, kept. The lock is not
+    /// held while `make` compiles.
+    fn get(&self, key: String, generation: u32, make: impl FnOnce() -> T) -> T {
+        if let Some((object, used)) = self
+            .map
+            .lock()
+            .unwrap_or_else(PoisonError::into_inner)
+            .get_mut(&key)
+        {
+            *used = generation;
+            return object.clone();
+        }
+        let object = make();
+        self.map
+            .lock()
+            .unwrap_or_else(PoisonError::into_inner)
+            .insert(key, (object.clone(), generation));
+        object
+    }
+    fn keep_only(&self, generation: u32) {
+        self.map
+            .lock()
+            .unwrap_or_else(PoisonError::into_inner)
+            .retain(|_, (_, used)| *used == generation);
+    }
+    fn len(&self) -> usize {
+        self.map
+            .lock()
+            .unwrap_or_else(PoisonError::into_inner)
+            .len()
+    }
+}
+
+/// The shader modules, layouts and pipelines of the device's renderers.
+#[derive(Default)]
+pub struct Reuse {
+    generation: std::sync::atomic::AtomicU32,
+    shaders: Kept<wgpu::ShaderModule>,
+    bind_group_layouts: Kept<wgpu::BindGroupLayout>,
+    pipeline_layouts: Kept<wgpu::PipelineLayout>,
+    render: Kept<wgpu::RenderPipeline>,
+}
+
+impl Reuse {
+    /// A renderer starts building: what it asks for is kept, the rest is let
+    /// go by [`Reuse::finish`].
+    pub fn begin(&self) -> u32 {
+        self.generation
+            .fetch_add(1, std::sync::atomic::Ordering::Relaxed)
+            .wrapping_add(1)
+    }
+    /// The renderer of `generation` is built: objects only older renderers
+    /// used are dropped here (the renderers still alive hold their own).
+    pub fn finish(&self, generation: u32) {
+        self.shaders.keep_only(generation);
+        self.bind_group_layouts.keep_only(generation);
+        self.pipeline_layouts.keep_only(generation);
+        self.render.keep_only(generation);
+    }
+    /// How many objects are kept.
+    pub fn len(&self) -> usize {
+        self.shaders.len()
+            + self.bind_group_layouts.len()
+            + self.pipeline_layouts.len()
+            + self.render.len()
+    }
+    fn current(&self) -> u32 {
+        self.generation.load(std::sync::atomic::Ordering::Relaxed)
+    }
+    /// `device`'s `create_*` calls through this cache.
+    pub fn on<'a>(&'a self, device: &'a wgpu::Device) -> On<'a> {
+        On {
+            reuse: self,
+            device,
+            generation: self.current(),
+        }
+    }
+}
+
+/// A device whose shader modules, layouts and render pipelines come from a
+/// [`Reuse`] when one with the same descriptor is kept.
+pub struct On<'a> {
+    reuse: &'a Reuse,
+    device: &'a wgpu::Device,
+    generation: u32,
+}
+impl On<'_> {
+    pub fn create_shader_module(
+        &self,
+        descriptor: wgpu::ShaderModuleDescriptor<'_>,
+    ) -> wgpu::ShaderModule {
+        let key = format!("{descriptor:?}");
+        self.reuse.shaders.get(key, self.generation, || {
+            self.device.create_shader_module(descriptor)
+        })
+    }
+    pub fn create_bind_group_layout(
+        &self,
+        descriptor: &wgpu::BindGroupLayoutDescriptor<'_>,
+    ) -> wgpu::BindGroupLayout {
+        let key = format!("{descriptor:?}");
+        self.reuse.bind_group_layouts.get(key, self.generation, || {
+            self.device.create_bind_group_layout(descriptor)
+        })
+    }
+    pub fn create_pipeline_layout(
+        &self,
+        descriptor: &wgpu::PipelineLayoutDescriptor<'_>,
+    ) -> wgpu::PipelineLayout {
+        let key = format!("{descriptor:?}");
+        self.reuse.pipeline_layouts.get(key, self.generation, || {
+            self.device.create_pipeline_layout(descriptor)
+        })
+    }
+    pub fn create_render_pipeline(
+        &self,
+        descriptor: &wgpu::RenderPipelineDescriptor<'_>,
+    ) -> wgpu::RenderPipeline {
+        let key = format!("{descriptor:?}");
+        self.reuse.render.get(key, self.generation, || {
+            self.device.create_render_pipeline(descriptor)
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Kept;
+
+    /// A key asked for again gets the kept object without making one; what
+    /// the latest generation did not ask for is let go when it finishes.
+    #[test]
+    fn kept_objects_are_shared_until_a_build_stops_asking() {
+        let kept = Kept::<u32>::default();
+        let made = std::cell::Cell::new(0);
+        let make = |value| {
+            made.set(made.get() + 1);
+            value
+        };
+        assert_eq!(kept.get("a".into(), 1, || make(10)), 10);
+        assert_eq!(kept.get("b".into(), 1, || make(20)), 20);
+        kept.keep_only(1);
+        assert_eq!(kept.len(), 2);
+        // The next build asks for "a" only.
+        assert_eq!(kept.get("a".into(), 2, || make(11)), 10);
+        kept.keep_only(2);
+        assert_eq!(kept.len(), 1);
+        assert_eq!(kept.get("b".into(), 3, || make(21)), 21);
+        assert_eq!(made.get(), 3);
+    }
+}

crates/horizon-client-render/src/gfx/submit.rs

@@ -7,8 +7,9 @@
 //! ([`Deref`]) first waits for that frame to be submitted, so writes, copies and
 //! submissions keep the order they had on one thread.
 use std::ops::Deref;
-use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
 use std::sync::{Mutex, mpsc};
+use std::time::{Duration, Instant};
 
 /// Whether frames go to the submit thread, unless `HORIZON_SUBMIT_THREAD` says (`0` off, `1` on):
 /// on Linux, where it was measured faster (+32% FPS in a CPU-bound view on Vulkan, #5779). On
@@ -50,6 +51,9 @@ pub struct Queue {
     /// A frame went to the submit thread and has not been waited for.
     pending: AtomicBool,
     landing: Mutex<Option<Landing>>,
+    /// Nanoseconds the window's thread waited for the submit thread since the last
+    /// [`take_waited`](Self::take_waited): the GPU or the display holding a frame back, not work.
+    waited: AtomicU64,
 }
 
 impl Queue {
@@ -60,6 +64,7 @@ impl Queue {
             thread: None,
             pending: AtomicBool::new(false),
             landing: Mutex::new(None),
+            waited: AtomicU64::new(0),
         };
         if !threaded {
             return this;
@@ -130,15 +135,24 @@ impl Queue {
             return;
         }
         if let Some(l) = landing.as_mut() {
+            let started = Instant::now();
             // A thread that died (a wgpu panic on it) panics here, as it would have in place.
             let submission = l
                 .done
                 .recv()
                 .expect("Horizon renderer: the submit thread stopped");
             l.landed = Some(submission);
+            let nanos = u64::try_from(started.elapsed().as_nanos()).unwrap_or(u64::MAX);
+            self.waited.fetch_add(nanos, Ordering::Relaxed);
         }
         self.pending.store(false, Ordering::Release);
     }
+    /// How long the window's thread waited for the submit thread since the last call: in a
+    /// GPU-bound view, the previous frame's submission and present hold up every use of the
+    /// queue (uploads in the frame's first half too), and that is waiting, not the frame's work.
+    pub fn take_waited(&self) -> Duration {
+        Duration::from_nanos(self.waited.swap(0, Ordering::Relaxed))
+    }
     /// The submission of the frame [`submit_later`](Self::submit_later) took, once it is
     /// made; `None` if it was taken already.
     pub fn landed(&self) -> Option<wgpu::SubmissionIndex> {

crates/horizon-client-render/src/gfx/world_post.rs

@@ -10,6 +10,8 @@
 
 use glam::{DMat4, DVec3, Mat4, Vec2};
 
+/// The least a world is scaled to when memory runs out.
+const MIN_SCALE: f32 = 0.25;
 /// The TAA history format: 8 bits would band as frames accumulate.
 const HISTORY_FORMAT: wgpu::TextureFormat = wgpu::TextureFormat::Rgba16Float;
 
@@ -322,12 +324,65 @@ impl Post {
             self.target = None;
             return None;
         }
-        let (size, output) = self.sizes(window);
-        let history_size = self.taa_on.then_some(output);
-        if self
-            .target
+        // The old target goes first: a slider drag would otherwise hold the old and the new
+        // targets together, and the sum is what runs a small GPU out of memory.
+        loop {
+            let (size, output) = self.sizes(window);
+            let history_size = self.taa_on.then_some(output);
+            if self
+                .target
+                .as_ref()
+                .is_some_and(|t| t.size == size && t.taa.as_ref().map(|h| h.size) == history_size)
+            {
+                break;
+            }
+            self.target = None;
+            // Errors raised are fatal, so catch an out-of-memory one and scale down. A texture
+            // that failed is invalid, so its view fails validation too: catch that as well.
+            let validation = device.push_error_scope(wgpu::ErrorFilter::Validation);
+            let memory = device.push_error_scope(wgpu::ErrorFilter::OutOfMemory);
+            let target = self.build_target(device, size, history_size);
+            let error = pollster::block_on(memory.pop()).or(pollster::block_on(validation.pop()));
+            if error.is_none() {
+                // New textures: no history yet.
+                self.taa_this_frame.jitter[2] = 1.0;
+                self.target = Some(target);
+                break;
+            }
+            drop(target);
+            if self.scale <= MIN_SCALE {
+                log::warn!(
+                    "Horizon renderer: no video memory for the scaled world at {size:?} ({}); drawing at the window's size",
+                    error.map_or_else(String::new, |e| e.to_string())
+                );
+                self.scale = 1.0;
+                self.target = None;
+                return None;
+            }
+            let reduced = (self.scale * 0.75).max(MIN_SCALE);
+            log::warn!(
+                "Horizon renderer: out of video memory for the scaled world at {size:?}; resolution scale {:.2} -> {reduced:.2} ({})",
+                self.scale,
+                error.map_or_else(String::new, |e| e.to_string())
+            );
+            self.scale = reduced;
+            if self.scale == 1.0 && !self.antialias && !self.taa_on && !always {
+                return None;
+            }
+        }
+        self.target
             .as_ref()
-            .is_none_or(|t| t.size != size || t.taa.as_ref().map(|h| h.size) != history_size)
+            .map(|t| (t.color.clone(), t.depth.clone()))
+    }
+
+    /// The world's colour and depth targets at `size`, and TAA's history when `history_size`
+    /// is set.
+    fn build_target(
+        &self,
+        device: &wgpu::Device,
+        size: [u32; 2],
+        history_size: Option<[u32; 2]>,
+    ) -> WorldTarget {
         {
             let make_tex = |label, size: [u32; 2], format, usage| {
                 device.create_texture(&wgpu::TextureDescriptor {
@@ -403,19 +458,14 @@ impl Post {
                     show,
                 })
             });
-            // New textures: no history yet.
-            self.taa_this_frame.jitter[2] = 1.0;
-            self.target = Some(WorldTarget {
+            WorldTarget {
                 size,
                 color,
                 depth,
                 group,
                 taa,
-            });
+            }
         }
-        self.target
-            .as_ref()
-            .map(|t| (t.color.clone(), t.depth.clone()))
     }
 
     /// The size of the world's own target, when it has one.

crates/horizon-client-render/src/graphics.rs

@@ -19,20 +19,28 @@ pub const HDR_MARKER: &str = "horizon-hdr-pending";
 pub struct Reported {
     pub paper_white: u32,
     pub peak: u32,
+    /// The display's darkest black, in hundredths of a nit.
+    pub black: u32,
 }
 
-static REPORTED: [AtomicU32; 2] = [AtomicU32::new(0), AtomicU32::new(0)];
+static REPORTED: [AtomicU32; 3] = [AtomicU32::new(0), AtomicU32::new(0), AtomicU32::new(0)];
 
 /// Sets what the system reports (the renderer, when it opens its surface).
 pub fn report(reported: Option<Reported>) {
-    let (paper_white, peak) = reported.map_or((0, 0), |r| (r.paper_white, r.peak));
+    let (paper_white, peak, black) =
+        reported.map_or((0, 0, 0), |r| (r.paper_white, r.peak, r.black));
     REPORTED[0].store(paper_white, Ordering::Relaxed);
     REPORTED[1].store(peak, Ordering::Relaxed);
+    REPORTED[2].store(black, Ordering::Relaxed);
 }
 /// What the system reports, if it does.
 pub fn reported() -> Option<Reported> {
-    let [paper_white, peak] = REPORTED.each_ref().map(|n| n.load(Ordering::Relaxed));
-    (peak > 0).then_some(Reported { paper_white, peak })
+    let [paper_white, peak, black] = REPORTED.each_ref().map(|n| n.load(Ordering::Relaxed));
+    (peak > 0).then_some(Reported {
+        paper_white,
+        peak,
+        black,
+    })
 }
 
 /// Simple-level presets. `Custom` leaves every option as the player set it.
@@ -582,8 +590,9 @@ pub struct Graphics {
     /// HDR peak brightness the world's highlights reach, in nits; 0 is Auto:
     /// what the system reports for the display ([`Graphics::peak_nits`]).
     pub hdr_peak: u32,
-    /// HDR black level: the display's darkest black, in hundredths of a nit (0 for
-    /// an OLED's true black). Shadows are lifted onto it, and the HDR metadata says it.
+    /// HDR black level: the display's darkest black, in hundredths of a nit; 0 is Auto:
+    /// what the system reports, else true black. Shadows are lifted onto it, and the HDR
+    /// metadata says it.
     pub hdr_black_level: u32,
     /// HDR brightness of the HUD and menus, in percent of paper white (25..=100); the
     /// first-person hand stays at the world's.
@@ -830,6 +839,14 @@ impl Graphics {
             n => n,
         }
     }
+    /// The black level, in nits: the player's, or on Auto what the system reports, else 0.
+    pub fn black_level_nits(&self) -> f32 {
+        let hundredths = match self.hdr_black_level {
+            0 => reported().map_or(0, |r| r.black),
+            n => n,
+        };
+        hundredths as f32 / 100.0
+    }
     /// Worker threads for chunk generation and meshing.
     pub fn worker_threads(&self) -> usize {
         if self.workers > 0 {

crates/horizon-client-render/src/graphics_ui.rs

@@ -606,24 +606,21 @@ impl H {
             H::HdrPaperWhite => match g.hdr_paper_white {
                 0 => labelled(
                     "Paper White",
-                    lang::tr("Auto (%s nits)", &[&g.paper_white_nits()]),
+                    lang::tr("Auto (%s)", &[&g.paper_white_nits()]),
                 ),
-                n => labelled("Paper White", lang::tr("%s nits", &[&n])),
+                n => labelled("Paper White", n.to_string()),
             },
             H::HdrPeak => match g.hdr_peak {
-                0 => labelled(
-                    "Peak Brightness",
-                    lang::tr("Auto (%s nits)", &[&g.peak_nits()]),
-                ),
-                n => labelled("Peak Brightness", lang::tr("%s nits", &[&n])),
+                0 => labelled("Peak Brightness", lang::tr("Auto (%s)", &[&g.peak_nits()])),
+                n => labelled("Peak Brightness", n.to_string()),
             },
-            H::HdrBlackLevel => labelled(
-                "Black Level",
-                lang::tr(
-                    "%s nits",
-                    &[&format!("{:.2}", g.hdr_black_level as f32 / 100.0)],
+            H::HdrBlackLevel => match g.hdr_black_level {
+                0 => labelled(
+                    "Black Level",
+                    lang::tr("Auto (%s)", &[&format!("{:.2}", g.black_level_nits())]),
                 ),
-            ),
+                n => labelled("Black Level", format!("{:.2}", n as f32 / 100.0)),
+            },
             H::HdrUiBrightness => labelled("UI Brightness", format!("{}%", g.hdr_ui_brightness)),
             H::HdrKey => {
                 Text::translate("Shortcut: %s", &[crate::keybinds::display_name(&g.hdr_key)])
@@ -2229,4 +2226,112 @@ mod tests {
             }
         }
     }
+    /// Horizon's graphics captions are English sentences that the language table keys by
+    /// themselves, so a caption, description or value that is not in `en_us.json` shows in
+    /// English in every language. Every text the three pages show, with each setting cycled
+    /// through its values (#1927).
+    #[test]
+    fn every_graphics_text_is_in_the_language_table() {
+        let (_, missed) = lang::scoped(lang::Language::load(&[], "de_de"), || {
+            for hdr in [false, true] {
+                let mut s = Settings::default();
+                s.horizon.hdr = hdr;
+                s.horizon.taa = true;
+                for level in [Level::Simple, Level::Advanced, Level::Hdr] {
+                    for _ in 0..8 {
+                        for row in extra_rows(level, &s) {
+                            match row {
+                                Row::Header(name) => {
+                                    lang::get(name);
+                                }
+                                Row::Setting(row) => {
+                                    row.item.label(&s);
+                                    let text = description(row.item, &s, row.text);
+                                    lang::get(text);
+                                    lang::get(row.cost.label());
+                                    if let Some(why) = row.item.blocked(&s) {
+                                        lang::get(why);
+                                    }
+                                }
+                            }
+                        }
+                        for row in extra_rows(level, &s) {
+                            if let Row::Setting(Setting {
+                                item: Item::Horizon(h),
+                                ..
+                            }) = row
+                            {
+                                h.cycle(&mut s, false);
+                            }
+                        }
+                    }
+                }
+            }
+            for button in ["Advanced...", "Simple...", "Done"] {
+                lang::get(button);
+            }
+        });
+        // `labelled` also looks up values that are already words in the language ("An") or
+        // numbers with a unit ("12 chunks", "Auto (8)"); those are not keys, and "FSR 3.1" is
+        // a name.
+        let missed: Vec<_> = missed
+            .into_iter()
+            .filter(|m| !m.starts_with(|c: char| c.is_ascii_digit()) && !m.starts_with("Auto ("))
+            .filter(|m| !["An", "Aus", "FSR 3.1", "key.keyboard.unknown"].contains(&m.as_str()))
+            .collect();
+        assert_eq!(missed, Vec::<String>::new());
+    }
+    /// Leaf Culling, Frame Generation and Shadow Cache came with English captions only (#1927).
+    #[test]
+    fn newer_graphics_settings_are_translated() {
+        let mut s = Settings::default();
+        s.horizon.leaf_culling = LeafCullingMode::Hollow;
+        s.horizon.entity_culling = EntityCullingMode::Asynchronous;
+        for (code, leaf, entity, leaf_text) in [
+            (
+                "de_de",
+                "Laub-Culling: Hohl",
+                "Objekt-Culling: Asynchron",
+                "Lässt Flächen zwischen Blättern weg: schneller, aber Lücken sind durchsichtig.",
+            ),
+            (
+                "pl_pl",
+                "Pomijanie liści: Puste",
+                "Pomijanie bytów: Asynchroniczne",
+                "Pomija ściany między liśćmi: szybciej, ale luki są przezroczyste.",
+            ),
+            (
+                "uk_ua",
+                "Відсікання листя: Порожнє",
+                "Відсік. сутностей: Асинхронно",
+                "Прибирає грані між листям: швидше, але прогалини прозорі.",
+            ),
+            (
+                "zh_cn",
+                "树叶剔除: 镂空",
+                "实体剔除: 异步",
+                "省略树叶之间的面：更快，但缝隙会透视。",
+            ),
+            (
+                "fr_fr",
+                "Occlusion feuillage: Creux",
+                "Occlusion des entités: Asynchrone",
+                "Supprime les faces entre feuilles : plus rapide, mais on voit à travers les trous.",
+            ),
+        ] {
+            let (shown, _) = lang::scoped(lang::Language::load(&[], code), || {
+                let item = |h| Item::Horizon(h);
+                (
+                    item(H::LeafCulling).label(&s).plain(),
+                    item(H::EntityCulling).label(&s).plain(),
+                    lang::get(description(item(H::LeafCulling), &s, "")),
+                )
+            });
+            assert_eq!(
+                shown,
+                (leaf.into(), entity.into(), leaf_text.into()),
+                "{code}"
+            );
+        }
+    }
 }

crates/horizon-client-render/src/hdr.wgsl

@@ -20,6 +20,8 @@ struct Params {
     black: f32,
     // The HUD and menus' brightness as a share of paper white.
     ui: f32,
+    // HDR lighting: what the strongest light multiplies a surface by, 1 for none.
+    scene: f32,
     // Per tier, low to very bright (hdr.rs `Tier`): the share of the headroom
     // its fully lifted pixels get.
     share: vec4<f32>,
@@ -53,7 +55,7 @@ fn shows_world(c: vec3<f32>, w: vec3<f32>) -> bool {
         return true;
     }
     let f = (c.r + c.g + c.b) / max(w.r + w.g + w.b, 1.0 / 255.0);
-    return f <= 1.01 && f > 0.5 && all(abs(c - f * w) <= 0.03 * w + 1.0 / 255.0);
+    return f <= 1.01 && f > 0.02 && all(abs(c - f * w) <= 0.03 * w + 1.0 / 255.0);
 }
 
 // Linear BT.709 to BT.2020 (ITU-R BT.2087), columns first.
@@ -168,8 +170,23 @@ fn calibration_nits(p: vec2<f32>, size: vec2<f32>) -> f32 {
     // lower the brighter, and where in the band how much (hdr_mark). The hand
     // writes its own alpha there (Hdr::hand_light_view): 1, or a light source it holds.
     var lifted = false;
-    if params.world > 0.5 && params.peak > 1.0 && w.a < 0.75
-        && (hand || (!covered && shows_world(c, w.rgb))) {
+    let shows = params.world > 0.5 && params.peak > 1.0
+        && (hand || (!covered && shows_world(c, w.rgb)));
+    // HDR lighting: alpha between 0.76 and 1 is how much of it the surface gets. Vanilla's
+    // light is albedo times lightmap, so this is the lightmap going past 1. It eases into the
+    // peak from 60% of it, so bright textures keep their detail.
+    if shows && w.a >= 0.75 {
+        let top = max(light.r, max(light.g, light.b));
+        let gain = 1.0 + (params.scene - 1.0) * (1.0 - w.a) / 0.24;
+        let v = top * gain;
+        let knee = max(0.6 * params.peak, 1.0);
+        var out = v;
+        if v > knee && params.peak > knee {
+            out = knee + (params.peak - knee) * (1.0 - exp(-(v - knee) / (params.peak - knee)));
+        }
+        light *= select(gain, out / max(top, 1e-4), v > knee);
+    }
+    if shows && w.a < 0.75 {
         let band = u32(clamp(floor((w.a + 0.005) / 0.175), 0.0, 3.0));
         let tier = 3u - band;
         let lift = 1.0 - clamp((w.a - 0.175 * f32(band)) / 0.165, 0.0, 1.0);

crates/horizon-client-render/src/hdr_calibration.rs

@@ -49,7 +49,7 @@ pub struct Calibration {
     values: [f32; 3],
     /// Which values were Auto (peak, paper white): saved as Auto again unless the
     /// player moved them.
-    auto: [Option<f32>; 2],
+    auto: [Option<f32>; 3],
     dragging: bool,
 }
 
@@ -125,11 +125,12 @@ impl Calibration {
         Self {
             step: 0,
             values: [
-                g.hdr_black_level as f32 / 100.0,
+                g.black_level_nits(),
                 g.peak_nits() as f32,
                 g.paper_white_nits() as f32,
             ],
             auto: [
+                (g.hdr_black_level == 0).then_some(g.black_level_nits()),
                 (g.hdr_peak == 0).then_some(g.peak_nits() as f32),
                 (g.hdr_paper_white == 0).then_some(g.paper_white_nits() as f32),
             ],
@@ -146,15 +147,11 @@ impl Calibration {
     fn label(&self) -> Text {
         let v = self.values[self.step];
         let step = self.current();
-        let nits = match step {
+        let value = match step {
             Step::Black => format!("{v:.2}"),
             _ => format!("{v:.0}"),
         };
-        Text::literal(format!(
-            "{}: {}",
-            step.name(),
-            lang::tr("%s nits", &[&nits])
-        ))
+        Text::literal(format!("{}: {}", step.name(), value))
     }
     /// The step, its nits and where the controls start (a share of the height), for
     /// HDR output's test picture.
@@ -284,11 +281,12 @@ impl Calibration {
     /// Writes what the player landed on into Horizon's settings.
     pub fn save(&self, s: &mut Settings) {
         let g = &mut s.horizon;
-        g.hdr_black_level = (self.values[0] * 100.0).round() as u32;
-        let [peak, paper_white] = [1, 2].map(|i| match self.auto[i - 1] {
+        let scale = [100.0, 1.0, 1.0];
+        let [black, peak, paper_white] = [0, 1, 2].map(|i| match self.auto[i] {
             Some(auto) if auto == self.values[i] => 0,
-            _ => self.values[i].round() as u32,
+            _ => (self.values[i] * scale[i]).round() as u32,
         });
+        g.hdr_black_level = black;
         g.hdr_peak = peak;
         g.hdr_paper_white = paper_white;
     }

crates/horizon-client-render/src/hud.rs

@@ -10,6 +10,7 @@ use std::{
 };
 use wgpu::util::DeviceExt;
 
+pub mod cit_glint;
 mod pack_text;
 
 /// A sprite's atlas region, and its size in GUI pixels: the size of the
@@ -247,16 +248,23 @@ fn wrap_border((name, w, h, data): &PackedImage) -> PackedImage {
     }
     (name.clone(), bw, bh, out)
 }
-/// The textures the enabled packs' Custom Item Textures item rules draw, under their
-/// `cit_assets` ids, beyond those already packed; with their flags and whether they animate.
-/// They are item textures, so an animated strip keeps its first frame. None without
-/// `optifine/cit` rules.
+/// The textures the enabled packs' Custom Item Textures rules draw, beyond those already packed:
+/// item rules' textures and their JSON models', armour and elytra rules' textures, under their
+/// `cit_assets` ids, with their flags and whether they animate. An animated strip keeps its
+/// first frame; a still texture is packed whole. None without `optifine/cit` rules.
 fn cit_sprites(
     root: &Path,
     packed: &[PackedImage],
 ) -> Vec<(PackedImage, Option<TextureFlags>, bool)> {
     let have: HashSet<&str> = packed.iter().map(|i| i.0.as_str()).collect();
-    let ids: Vec<String> = crate::cit_assets::item_sprites(&crate::cit::load_rules(root))
+    let rules = crate::cit::load_rules(root);
+    let mut ids = crate::cit_assets::item_sprites(&rules);
+    if !rules.is_empty() {
+        let models = crate::cit_assets::load_models(root, &rules);
+        ids.extend(crate::cit_assets::model_sprites(&models));
+        ids.extend(crate::cit_armor::armor_sprites(&rules));
+    }
+    let ids: Vec<String> = ids
         .into_iter()
         // Vanilla's sprites are packed without their namespace, as `sprite_name` looks them up;
         // Horizon's own (`horizon/white`, the run-time slots) are added after, and stay its own.
@@ -664,25 +672,21 @@ impl HudAtlas {
     /// packs fill a 4096-wide atlas past what GPUs allow (Faithful 64x needs
     /// 32768 rows); vanilla's stitcher fails the reload when its atlases don't
     /// fit, and the packs are then turned off (`Minecraft.clearResourcePacksOnError`).
+    /// A width where the plain shelves (each image after the last) leave too
+    /// much unused is tried again with each image in the first shelf with
+    /// room: a pack of thousands of mixed sizes (server packs with custom
+    /// items) fits where the shelves' ragged ends would not.
     fn layout(images: &[PackedImage], max: u32) -> Result<(u32, Vec<(u32, u32)>, u32)> {
         let mut width = 4096.min(max);
         loop {
-            let mut placements = Vec::with_capacity(images.len());
-            let (mut x, mut y, mut row) = (0u32, 0u32, 0u32);
-            for (_, w, h, _) in images {
-                if x + w + 1 > width {
-                    x = 0;
-                    y += row + 1;
-                    row = 0;
-                }
-                placements.push((x, y));
-                x += w + 1;
-                row = row.max(*h);
-            }
-            let glyph_region = y + row + 1;
             let wide_enough = images.iter().all(|i| i.1 < width);
-            if wide_enough && glyph_region + GLYPH_ROWS <= max {
-                return Ok((width, placements, glyph_region));
+            if wide_enough {
+                for first_fit in [false, true] {
+                    let (placements, glyph_region) = Self::shelves(images, width, first_fit);
+                    if glyph_region + GLYPH_ROWS <= max {
+                        return Ok((width, placements, glyph_region));
+                    }
+                }
             }
             if width >= max {
                 let texels: u64 = images.iter().map(|i| u64::from(i.1) * u64::from(i.2)).sum();
@@ -695,6 +699,33 @@ impl HudAtlas {
             width = (width * 2).min(max);
         }
     }
+    /// `layout`'s shelves at one width: the placements and the first row below
+    /// them. `first_fit` puts an image in the first shelf that is tall enough
+    /// and has room, instead of only the last one.
+    fn shelves(images: &[PackedImage], width: u32, first_fit: bool) -> (Vec<(u32, u32)>, u32) {
+        // Each shelf: its top row, its height (its first image's) and the next free column.
+        let mut shelves: Vec<(u32, u32, u32)> = Vec::new();
+        let mut placements = Vec::with_capacity(images.len());
+        for (_, w, h, _) in images {
+            let open = if first_fit {
+                shelves.iter().position(|s| s.1 >= *h && s.2 + w < width)
+            } else {
+                shelves
+                    .len()
+                    .checked_sub(1)
+                    .filter(|&i| shelves[i].1 >= *h && shelves[i].2 + w < width)
+            };
+            let i = open.unwrap_or_else(|| {
+                let top = shelves.last().map_or(0, |s| s.0 + s.1 + 1);
+                shelves.push((top, *h, 0));
+                shelves.len() - 1
+            });
+            placements.push((shelves[i].2, shelves[i].0));
+            shelves[i].2 += w + 1;
+        }
+        let glyph_region = shelves.last().map_or(1, |s| s.0 + s.1 + 1);
+        (placements, glyph_region)
+    }
     /// Pack the textures under these folders of `textures/`, and for the
     /// `full` atlas the generated sprites and the run-time slots too.
     fn pack(root: &Path, defaults: &Path, folders: &[&str], full: bool) -> Result<Self> {
@@ -1155,6 +1186,9 @@ pub enum Blend {
     /// `RenderPipelines.END_PORTAL` as a GUI fill: the End portal's layers
     /// projected from the screen (`HudBatch::end_portal` sets the textures).
     EndPortal,
+    /// An OptiFine CIT glint layer (`cit_glint`), blended as entry `n` of
+    /// `GlintTextures::blends` says.
+    CitGlint(u8),
 }
 /// What a `Blend::EndPortal` fill samples: the atlas rects (u0, v0, width,
 /// height) of `end_sky.png` and `end_portal.png`, and the `GameTime` uniform.
@@ -1889,7 +1923,11 @@ pub struct HudRenderer {
     depth_pipeline: wgpu::RenderPipeline,
     vignette_pipeline: wgpu::RenderPipeline,
     end_portal_pipeline: wgpu::RenderPipeline,
+    /// The layout of `group`, which the CIT glint pipelines share.
+    layout: wgpu::BindGroupLayout,
     group: wgpu::BindGroup,
+    /// The pack's CIT enchantment glints, when it has any.
+    cit_glint: Option<cit_glint::CitGlintPass>,
     uniform: wgpu::Buffer,
     buffer: wgpu::Buffer,
     capacity: u64,
@@ -2122,7 +2160,9 @@ impl HudRenderer {
             depth_pipeline,
             vignette_pipeline,
             end_portal_pipeline,
+            layout,
             group,
+            cit_glint: None,
             uniform,
             buffer,
             capacity,
@@ -2132,6 +2172,18 @@ impl HudRenderer {
             zoom: 1.0,
         })
     }
+    /// Draw the CIT glint layers of `textures` (the pack's enchantment rules); `None` or no
+    /// textures draws none.
+    pub fn set_cit_glints(
+        &mut self,
+        device: &wgpu::Device,
+        queue: &wgpu::Queue,
+        textures: Option<&cit_glint::GlintTextures>,
+    ) {
+        self.cit_glint = textures.and_then(|t| {
+            cit_glint::CitGlintPass::new(device, queue, self.format, &self.layout, t)
+        });
+    }
     /// Draw the GUI's text with `shader` (`HudAtlas::text_shader`), or natively.
     pub fn set_text_shader(
         &mut self,
@@ -2367,6 +2419,12 @@ impl HudRenderer {
                     Blend::Depth(_) => &self.depth_pipeline,
                     Blend::Vignette => &self.vignette_pipeline,
                     Blend::EndPortal => &self.end_portal_pipeline,
+                    Blend::CitGlint(blend) => {
+                        if let Some(cit) = &self.cit_glint {
+                            cit.draw(&mut pass, *blend, range.clone());
+                        }
+                        continue;
+                    }
                 };
                 match &self.pack_text {
                     Some(pack_text) if *blend == Blend::Alpha => {
@@ -2827,6 +2885,25 @@ mod tests {
         assert_eq!(texel_at(&atlas, rect, 1, 1), [10, 200, 30, 255]);
     }
     #[test]
+    fn a_cit_models_relative_texture_is_packed() {
+        let root = cit_root(
+            "model",
+            &[
+                ("a.properties", "items=stick\nmodel=sword"),
+                (
+                    "sword.json",
+                    r#"{"parent":"item/generated","textures":{"layer0":"./blade"}}"#,
+                ),
+            ],
+        );
+        let cit = root.join("assets/minecraft/optifine/cit");
+        write_strip(&cit.join("blade.png"), 2, 2, &[[40, 50, 60, 255]], None);
+        let atlas = HudAtlas::build(&root).unwrap();
+        let _ = fs::remove_dir_all(&root);
+        let rect = atlas.sprites["horizon_cit:minecraft/optifine/cit/blade"];
+        assert_eq!(texel_at(&atlas, rect, 1, 1), [40, 50, 60, 255]);
+    }
+    #[test]
     fn a_still_cit_texture_is_packed_whole() {
         // Not cut to a square as an unmarked strip would be: armour layers are 2:1.
         let root = cit_root("still", &[("a.properties", "items=stick\ntexture=a")]);
@@ -2862,7 +2939,7 @@ mod tests {
         assert_eq!(animations[0].1.frame_count(), 3);
     }
     #[test]
-    fn a_texture_only_an_armor_rule_names_is_not_packed() {
+    fn an_armor_rules_texture_is_packed_too() {
         let root = cit_root(
             "armor",
             &[(
@@ -2872,11 +2949,15 @@ mod tests {
         );
         let cit = root.join("assets/minecraft/optifine/cit");
         write_strip(&cit.join("a.png"), 64, 32, &[[1, 2, 3, 255]], None);
-        // The rule loads; only its kind keeps the texture out.
-        assert_eq!(crate::cit::load_rules(&root).len(), 1);
+        let rules = crate::cit::load_rules(&root);
+        assert_eq!(rules.len(), 1);
         let atlas = HudAtlas::build(&root).unwrap();
         let _ = fs::remove_dir_all(&root);
-        assert!(!atlas.sprites.keys().any(|k| k.starts_with("horizon_cit:")));
+        // Worn armour draws from the same atlas, under the name the layer looks up.
+        let rect = atlas.sprites["horizon_cit:minecraft/optifine/cit/a"];
+        assert_eq!(rect.texels((atlas.width, atlas.height)), (64, 32));
+        let layer = crate::cit_armor::layer_sprite(&rules[0], "minecraft:iron", false, false);
+        assert!(atlas.sprites.contains_key(&layer.unwrap()));
     }
     #[test]
     fn named_cit_textures_pack_once_and_bad_ones_are_skipped() {
@@ -3104,6 +3185,19 @@ texture=wide",
         assert_inside(&images, width, &placements, free);
     }
     #[test]
+    fn mixed_sizes_fill_the_ends_of_the_shelves() {
+        // 15 images 9000 wide leave 7383 of a 16384 shelf unused each; the
+        // 4000-wide ones (same height) come after them, and on shelves of their
+        // own (4 to a shelf) the atlas is 19 shelves tall: past 16384 rows.
+        // Each in a gap, it is 15.
+        let mut images = sized(15, 9000, 1000);
+        images.extend(sized(15, 4000, 1000));
+        let (width, placements, free) = HudAtlas::layout(&images, 16384).unwrap();
+        assert_eq!(width, 16384);
+        assert!(free + GLYPH_ROWS <= 16384);
+        assert_inside(&images, width, &placements, free);
+    }
+    #[test]
     fn textures_that_cannot_fit_are_an_error_not_a_gpu_panic() {
         let error = HudAtlas::layout(&sized(300, 1024, 1024), MAX_ATLAS_SIZE).unwrap_err();
         assert!(error.to_string().contains("do not fit a 16384x16384 atlas"));

crates/horizon-client-render/src/hud.wgsl

@@ -41,6 +41,35 @@ struct Out {
     if c.a < 0.004 { discard; }
     return c;
 }
+// OptiFine CIT glint layers (hud/cit_glint.rs): every rule's texture in one array, the slot in
+// the vertex colour's red and the layer's intensity in its alpha. Masked by the item's texture
+// as the vanilla glint is, then blended by the pipeline the rule's `blend` asks for.
+struct CitSlot {
+    rgba: vec4<f32>,
+    // x: linear filtering (`blur`).
+    blur: vec4<f32>,
+}
+struct CitSlots {
+    slots: array<CitSlot, 256>,
+}
+@group(1) @binding(0) var cit_tex: texture_2d_array<f32>;
+@group(1) @binding(1) var cit_blur: sampler;
+@group(1) @binding(2) var cit_nearest: sampler;
+@group(1) @binding(3) var<uniform> cit: CitSlots;
+@fragment fn fs_cit_glint(in: Out) -> @location(0) vec4<f32> {
+    let mask = textureSample(atlas, atlas_sampler, in.uv).a;
+    let index = u32(round(in.color.r * 255.0));
+    let slot = cit.slots[index];
+    let blurred = textureSampleLevel(cit_tex, cit_blur, in.glint_uv, index, 0.0);
+    let sharp = textureSampleLevel(cit_tex, cit_nearest, in.glint_uv, index, 0.0);
+    if mask < 0.1 { discard; }
+    // The layer's colour times its intensity (the glint strength option included) in alpha,
+    // cut where vanilla's glint shader cuts, which CIT Resewn draws through.
+    var t = select(sharp, blurred, slot.blur.x > 0.5) * slot.rgba;
+    t.a *= in.color.a;
+    if t.a < 0.1 { discard; }
+    return t;
+}
 @fragment fn fs_crosshair(in: Out) -> @location(0) vec4<f32> {
     let c = textureSample(atlas, atlas_sampler, in.uv) * in.color;
     if c.a == 0.0 { discard; }

crates/horizon-client-render/src/hud/cit_glint.rs

@@ -0,0 +1,563 @@
+//! OptiFine CIT enchantment glints on GUI items (`type=enchantment`, see `crate::cit_glint` for
+//! which layers a stack draws): every rule's texture in one texture array, each layer an extra
+//! pass over the item's quads with its rule's blend. A layer's vertices carry its texture slot
+//! (red) and its intensity (alpha) in their colour; its scrolled UV is worked out on the CPU, as
+//! vanilla's glint's is. Without enchantment rules nothing here is made.
+
+use super::HudVertex;
+use horizon_optifine::cit::{Blend, Factor, Kind, Rule};
+use std::path::Path;
+
+/// Slots the shader's table holds; rules past it draw no layer (and match no stack).
+pub const MAX_SLOTS: usize = 256;
+/// The largest side the shared texture size takes: bigger glints are scaled down to it.
+const MAX_SIDE: u32 = 1024;
+/// The most the texture array takes, in bytes: past it the shared size is halved.
+const MAX_BYTES: u64 = 64 << 20;
+
+/// One slot's constants.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct Slot {
+    /// The rule's `r`, `g`, `b`, `a`.
+    pub rgba: [f32; 4],
+    /// Linear filtering (`blur`), else nearest.
+    pub blur: bool,
+    /// An index into `GlintTextures::blends`.
+    pub blend: u8,
+}
+
+/// The enchantment rules' textures, resized to one size.
+#[derive(Debug, Default)]
+pub struct GlintTextures {
+    pub width: u32,
+    pub height: u32,
+    /// One `width` x `height` RGBA image per slot, slot after slot. Kept after the upload: every
+    /// split-screen player's renderer builds its own array from it.
+    pub pixels: Vec<u8>,
+    /// Per rule (an index into `CitRules::rules`): its slot; `None` for other kinds of rules,
+    /// textures that did not load and rules past `MAX_SLOTS`.
+    pub slot_of: Vec<Option<u8>>,
+    pub slots: Vec<Slot>,
+    /// The blends the slots use, once each: the HUD makes a pipeline per entry.
+    pub blends: Vec<Option<Blend>>,
+}
+
+impl GlintTextures {
+    /// The textures of `rules` under the overlay resource root.
+    pub fn load(root: &Path, rules: &[Rule]) -> Self {
+        let mut images = Vec::new();
+        let mut past = 0;
+        for (i, rule) in rules.iter().enumerate() {
+            let Some(path) = rule.texture.as_deref() else {
+                continue;
+            };
+            if rule.kind != Kind::Enchantment {
+                continue;
+            }
+            if images.len() == MAX_SLOTS {
+                past += 1;
+                continue;
+            }
+            match super::decode(&root.join(path)) {
+                Ok(image) => images.push((i, image)),
+                Err(e) => log::warn!("custom item textures: glint {path} left out: {e}"),
+            }
+        }
+        if past > 0 {
+            log::warn!(
+                "custom item textures: {past} glint rules past the first {MAX_SLOTS} left out"
+            );
+        }
+        Self::new(rules, images, MAX_BYTES)
+    }
+
+    /// `images`: (rule, (width, height, RGBA)), in at most `budget` bytes.
+    fn new(rules: &[Rule], images: Vec<(usize, (u32, u32, Vec<u8>))>, budget: u64) -> Self {
+        let sizes = images.iter().map(|(_, (w, h, _))| (*w, *h));
+        let Some((width, height)) = shared_size(sizes, images.len(), budget) else {
+            return Self::default();
+        };
+        let mut out = Self {
+            width,
+            height,
+            slot_of: vec![None; rules.len()],
+            ..Self::default()
+        };
+        for (rule, (w, h, rgba)) in images {
+            let glint = &rules[rule].glint;
+            out.pixels
+                .extend(resize(&rgba, (w, h), (width, height), glint.blur));
+            let blend = match out.blends.iter().position(|b| *b == glint.blend) {
+                Some(i) => i,
+                None => {
+                    out.blends.push(glint.blend);
+                    out.blends.len() - 1
+                }
+            };
+            out.slot_of[rule] = Some(out.slots.len() as u8);
+            out.slots.push(Slot {
+                rgba: glint.rgba,
+                blur: glint.blur,
+                blend: blend as u8,
+            });
+        }
+        out
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.slots.is_empty()
+    }
+}
+
+/// The size every slot takes: the largest width and height of `sizes`, each at most
+/// `MAX_SIDE`, then halved until `layers` RGBA images of it fit in `budget` bytes.
+fn shared_size(
+    sizes: impl Iterator<Item = (u32, u32)>,
+    layers: usize,
+    budget: u64,
+) -> Option<(u32, u32)> {
+    let (mut w, mut h) = sizes.fold(None, |max: Option<(u32, u32)>, (w, h)| {
+        let (w, h) = (w.clamp(1, MAX_SIDE), h.clamp(1, MAX_SIDE));
+        Some(max.map_or((w, h), |(mw, mh)| (mw.max(w), mh.max(h))))
+    })?;
+    let bytes = |w: u32, h: u32| u64::from(w) * u64::from(h) * 4 * layers as u64;
+    while bytes(w, h) > budget && (w > 1 || h > 1) {
+        (w, h) = ((w / 2).max(1), (h / 2).max(1));
+    }
+    Some((w, h))
+}
+
+/// `rgba` (`from` texels) scaled to `to`: bilinearly for a `blur` glint, as the GPU would have
+/// filtered the texture at its own size, else to the nearest texel. Both wrap at the edges, as
+/// the glint repeats over the item.
+fn resize(rgba: &[u8], from: (u32, u32), to: (u32, u32), smooth: bool) -> Vec<u8> {
+    if from == to {
+        return rgba.to_vec();
+    }
+    let ((w, h), (to_w, to_h)) = (from, to);
+    let texel = |x: i64, y: i64| {
+        let (x, y) = (x.rem_euclid(i64::from(w)), y.rem_euclid(i64::from(h)));
+        let at = (y as usize * w as usize + x as usize) * 4;
+        &rgba[at..at + 4]
+    };
+    // Where texel `i` of `n` samples the source's `size` texels, in source texels.
+    let centre = |i: u32, n: u32, size: u32| (f64::from(i) + 0.5) * f64::from(size) / f64::from(n);
+    let mut out = Vec::with_capacity(to_w as usize * to_h as usize * 4);
+    for y in 0..to_h {
+        let sy = centre(y, to_h, h);
+        for x in 0..to_w {
+            let sx = centre(x, to_w, w);
+            if !smooth {
+                let pick = |i: u32, n: u32, size: u32| {
+                    (u64::from(i) * u64::from(size) / u64::from(n)) as i64
+                };
+                out.extend_from_slice(texel(pick(x, to_w, w), pick(y, to_h, h)));
+                continue;
+            }
+            let (fx, fy) = (sx - 0.5, sy - 0.5);
+            let (x0, y0) = (fx.floor() as i64, fy.floor() as i64);
+            let (tx, ty) = (fx - fx.floor(), fy - fy.floor());
+            let [a, b, c, d] = [
+                texel(x0, y0),
+                texel(x0 + 1, y0),
+                texel(x0, y0 + 1),
+                texel(x0 + 1, y0 + 1),
+            ];
+            let lerp =
+                |p: &[u8], q: &[u8], k: usize| f64::from(p[k]) * (1.0 - tx) + f64::from(q[k]) * tx;
+            out.extend((0..4).map(|k| {
+                let (top, bottom) = (lerp(a, b, k), lerp(c, d, k));
+                (top * (1.0 - ty) + bottom * ty).round() as u8
+            }));
+        }
+    }
+    out
+}
+
+/// CIT Resewn's glint texturing for one layer: `translation(-x, y)`, `rotateZ(rotation)`, then
+/// `scale`, where `x` and `y` run through vanilla's 110000 and 30000 periods of the clock
+/// `millis * speed` (vanilla's own glint runs at `millis * glintSpeed * 8`). `rotation` is in
+/// degrees, as OptiFine's doc has it.
+pub fn layer_uv(model: [f32; 2], millis: f32, speed: f32, rotation: f32, scale: f32) -> [f32; 2] {
+    let clock = f64::from(millis) * f64::from(speed);
+    let x = (clock % 110_000.0 / 110_000.0) as f32;
+    let y = (clock % 30_000.0 / 30_000.0) as f32;
+    let (sin, cos) = rotation.to_radians().sin_cos();
+    let (u, v) = (model[0] * scale, model[1] * scale);
+    [u * cos - v * sin - x, u * sin + v * cos + y]
+}
+
+/// The colour of a layer's vertices: its slot in red, its intensity in alpha.
+pub fn vertex_color(slot: u8, intensity: f32) -> u32 {
+    let alpha = (intensity.clamp(0.0, 1.0) * 255.0).round() as u8;
+    super::rgba(slot, 0, 0, alpha)
+}
+
+fn factor(f: Factor) -> wgpu::BlendFactor {
+    use wgpu::BlendFactor as W;
+    match f {
+        Factor::Zero => W::Zero,
+        Factor::One => W::One,
+        Factor::SrcColor => W::Src,
+        Factor::OneMinusSrcColor => W::OneMinusSrc,
+        Factor::SrcAlpha => W::SrcAlpha,
+        Factor::OneMinusSrcAlpha => W::OneMinusSrcAlpha,
+        Factor::DstAlpha => W::DstAlpha,
+        Factor::OneMinusDstAlpha => W::OneMinusDstAlpha,
+        Factor::DstColor => W::Dst,
+        Factor::OneMinusDstColor => W::OneMinusDst,
+        Factor::SrcAlphaSaturate => W::SrcAlphaSaturated,
+    }
+}
+
+/// `glBlendFuncSeparate` with the rule's factors; `replace` draws unblended.
+pub fn blend_state(blend: Option<Blend>) -> wgpu::BlendState {
+    let Some(b) = blend else {
+        return wgpu::BlendState::REPLACE;
+    };
+    let component = |src, dst| wgpu::BlendComponent {
+        src_factor: factor(src),
+        dst_factor: factor(dst),
+        operation: wgpu::BlendOperation::Add,
+    };
+    wgpu::BlendState {
+        color: component(b.src, b.dst),
+        alpha: component(b.src_alpha, b.dst_alpha),
+    }
+}
+
+/// The GPU side: the texture array and slot table (bind group 1 of `fs_cit_glint`), and one
+/// pipeline per blend.
+pub(super) struct CitGlintPass {
+    group: wgpu::BindGroup,
+    pipelines: Vec<wgpu::RenderPipeline>,
+}
+
+impl CitGlintPass {
+    /// `None` without textures. `hud` is the HUD's bind group layout (group 0).
+    pub(super) fn new(
+        device: &wgpu::Device,
+        queue: &wgpu::Queue,
+        format: wgpu::TextureFormat,
+        hud: &wgpu::BindGroupLayout,
+        textures: &GlintTextures,
+    ) -> Option<Self> {
+        use wgpu::util::DeviceExt;
+        if textures.is_empty() {
+            return None;
+        }
+        // wgpu's OpenGL backend makes 1 layer a 2D texture and 6n a cube map
+        // (`gfx::array_layers`): pad with empty layers, within the GPU's limit. Slots past the
+        // layers kept sample the last one.
+        let gl = device.adapter_info().backend == wgpu::Backend::Gl;
+        let max = device.limits().max_texture_array_layers.max(1);
+        let slots = textures.slots.len() as u32;
+        let mut kept = slots.min(max);
+        while kept > 1 && crate::gfx::array_layers(kept, gl) > max {
+            kept -= 1;
+        }
+        if kept < slots {
+            log::warn!("custom item textures: the GPU holds {kept} of {slots} glint textures");
+        }
+        let layers = crate::gfx::array_layers(kept, gl).min(max);
+        let layer_bytes = textures.width as usize * textures.height as usize * 4;
+        let mut data = std::borrow::Cow::Borrowed(&textures.pixels[..]);
+        if layers != slots {
+            let mut padded = textures.pixels[..layer_bytes * kept as usize].to_vec();
+            padded.resize(layer_bytes * layers as usize, 0);
+            data = std::borrow::Cow::Owned(padded);
+        }
+        let texture = device.create_texture_with_data(
+            queue,
+            &wgpu::TextureDescriptor {
+                label: Some("CIT glints"),
+                size: wgpu::Extent3d {
+                    width: textures.width,
+                    height: textures.height,
+                    depth_or_array_layers: layers,
+                },
+                mip_level_count: 1,
+                sample_count: 1,
+                dimension: wgpu::TextureDimension::D2,
+                format: wgpu::TextureFormat::Rgba8Unorm,
+                usage: wgpu::TextureUsages::TEXTURE_BINDING,
+                view_formats: &[],
+            },
+            wgpu::util::TextureDataOrder::LayerMajor,
+            &data,
+        );
+        let view = texture.create_view(&wgpu::TextureViewDescriptor {
+            dimension: Some(wgpu::TextureViewDimension::D2Array),
+            ..Default::default()
+        });
+        let sampler = |label, filter| {
+            device.create_sampler(&wgpu::SamplerDescriptor {
+                label: Some(label),
+                address_mode_u: wgpu::AddressMode::Repeat,
+                address_mode_v: wgpu::AddressMode::Repeat,
+                mag_filter: filter,
+                min_filter: filter,
+                ..Default::default()
+            })
+        };
+        let linear = sampler("CIT glint blur", wgpu::FilterMode::Linear);
+        let nearest = sampler("CIT glint", wgpu::FilterMode::Nearest);
+        // hud.wgsl's `CitSlot`: rgba, then blur in x.
+        let mut table = vec![[0.0f32; 8]; MAX_SLOTS];
+        for (row, slot) in table.iter_mut().zip(&textures.slots) {
+            row[..4].copy_from_slice(&slot.rgba);
+            row[4] = if slot.blur { 1.0 } else { 0.0 };
+        }
+        let table = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+            label: Some("CIT glint slots"),
+            contents: bytemuck::cast_slice(&table),
+            usage: wgpu::BufferUsages::UNIFORM,
+        });
+        let fragment = wgpu::ShaderStages::FRAGMENT;
+        let filtering = wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering);
+        let entry = |binding, ty| wgpu::BindGroupLayoutEntry {
+            binding,
+            visibility: fragment,
+            ty,
+            count: None,
+        };
+        let layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+            label: Some("CIT glint bindings"),
+            entries: &[
+                entry(
+                    0,
+                    wgpu::BindingType::Texture {
+                        sample_type: wgpu::TextureSampleType::Float { filterable: true },
+                        view_dimension: wgpu::TextureViewDimension::D2Array,
+                        multisampled: false,
+                    },
+                ),
+                entry(1, filtering),
+                entry(2, filtering),
+                entry(
+                    3,
+                    wgpu::BindingType::Buffer {
+                        ty: wgpu::BufferBindingType::Uniform,
+                        has_dynamic_offset: false,
+                        min_binding_size: None,
+                    },
+                ),
+            ],
+        });
+        let group = device.create_bind_group(&wgpu::BindGroupDescriptor {
+            label: Some("CIT glint resources"),
+            layout: &layout,
+            entries: &[
+                wgpu::BindGroupEntry {
+                    binding: 0,
+                    resource: wgpu::BindingResource::TextureView(&view),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 1,
+                    resource: wgpu::BindingResource::Sampler(&linear),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 2,
+                    resource: wgpu::BindingResource::Sampler(&nearest),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 3,
+                    resource: table.as_entire_binding(),
+                },
+            ],
+        });
+        let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
+            label: Some("Horizon HUD (CIT glints)"),
+            source: wgpu::ShaderSource::Wgsl(include_str!("../hud.wgsl").into()),
+        });
+        let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
+            label: Some("CIT glint layout"),
+            bind_group_layouts: &[Some(hud), Some(&layout)],
+            ..Default::default()
+        });
+        let attributes =
+            wgpu::vertex_attr_array![0=>Float32x2,1=>Float32x2,2=>Unorm8x4,3=>Float32,4=>Float32x2];
+        let pipelines = textures
+            .blends
+            .iter()
+            .map(|&blend| {
+                device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+                    label: Some("CIT glint"),
+                    layout: Some(&pipeline_layout),
+                    vertex: wgpu::VertexState {
+                        module: &shader,
+                        entry_point: Some("vs_main"),
+                        compilation_options: Default::default(),
+                        buffers: &[Some(wgpu::VertexBufferLayout {
+                            array_stride: std::mem::size_of::<HudVertex>() as u64,
+                            step_mode: wgpu::VertexStepMode::Vertex,
+                            attributes: &attributes,
+                        })],
+                    },
+                    primitive: Default::default(),
+                    depth_stencil: None,
+                    multisample: Default::default(),
+                    fragment: Some(wgpu::FragmentState {
+                        module: &shader,
+                        entry_point: Some("fs_cit_glint"),
+                        compilation_options: Default::default(),
+                        targets: &[Some(wgpu::ColorTargetState {
+                            format,
+                            blend: Some(blend_state(blend)),
+                            write_mask: wgpu::ColorWrites::ALL,
+                        })],
+                    }),
+                    multiview_mask: None,
+                    cache: None,
+                })
+            })
+            .collect();
+        Some(Self { group, pipelines })
+    }
+
+    /// Draw `vertices` with blend `blend` (an index into `GlintTextures::blends`).
+    pub(super) fn draw(
+        &self,
+        pass: &mut wgpu::RenderPass<'_>,
+        blend: u8,
+        vertices: std::ops::Range<u32>,
+    ) {
+        if let Some(pipeline) = self.pipelines.get(usize::from(blend)) {
+            pass.set_pipeline(pipeline);
+            pass.set_bind_group(1, &self.group, &[]);
+            pass.draw(vertices, 0..1);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use horizon_optifine::Properties;
+    use horizon_optifine::cit::parse_blend;
+
+    fn rule(name: &str, text: &str) -> Rule {
+        let path = format!("assets/minecraft/optifine/cit/{name}.properties");
+        let text = format!("texture=glint\n{text}");
+        Rule::parse(&path, &Properties::parse_equals_first(&text), |_| true).unwrap()
+    }
+
+    #[test]
+    fn slots_share_one_size_and_their_blends() {
+        let rules = [
+            rule("a", "type=enchantment\nr=0.5"),
+            rule("item", "items=stick"),
+            rule("b", "type=enchantment\nblend=multiply\nblur=false"),
+            rule("c", "type=enchantment"),
+        ];
+        // A 1x1 red glint and a 2x2 one: the red texel fills 2x2.
+        let red = vec![255, 0, 0, 255];
+        let quad: Vec<u8> = (0..16).collect();
+        let t = GlintTextures::new(
+            &rules,
+            vec![
+                (0, (1, 1, red)),
+                (2, (2, 2, quad.clone())),
+                (3, (2, 2, quad.clone())),
+            ],
+            MAX_BYTES,
+        );
+        assert_eq!((t.width, t.height), (2, 2));
+        assert_eq!(t.slot_of, [Some(0), None, Some(1), Some(2)]);
+        assert_eq!(&t.pixels[..16], [255, 0, 0, 255].repeat(4));
+        assert_eq!(&t.pixels[16..32], &quad[..]);
+        assert_eq!(
+            t.blends,
+            [
+                parse_blend("add").unwrap(),
+                parse_blend("multiply").unwrap()
+            ]
+        );
+        let blends: Vec<_> = t.slots.iter().map(|s| s.blend).collect();
+        assert_eq!(blends, [0, 1, 0]);
+        assert_eq!(t.slots[0].rgba, [0.5, 1.0, 1.0, 1.0]);
+        assert!(!t.slots[1].blur && t.slots[2].blur);
+        assert!(GlintTextures::new(&rules, Vec::new(), MAX_BYTES).is_empty());
+    }
+
+    #[test]
+    fn big_glints_are_scaled_down_to_the_largest_side() {
+        let rules = [rule("wide", "type=enchantment\nblur=false")];
+        // 2048 x 1, texel x holding x in red and green: every other texel is kept.
+        let wide: Vec<u8> = (0..2048u32)
+            .flat_map(|x| [(x % 256) as u8, (x / 256) as u8, 0, 255])
+            .collect();
+        let t = GlintTextures::new(&rules, vec![(0, (2048, 1, wide))], MAX_BYTES);
+        assert_eq!((t.width, t.height), (1024, 1));
+        for x in [0u32, 1, 300, 1023] {
+            let at = x as usize * 4;
+            let source = 2 * x;
+            let want = [(source % 256) as u8, (source / 256) as u8, 0, 255];
+            assert_eq!(t.pixels[at..at + 4], want, "texel {x}");
+        }
+    }
+
+    #[test]
+    fn the_array_is_halved_until_it_fits() {
+        let sizes = |n: usize| std::iter::repeat_n((1024, 1024), n);
+        // 16 layers of 1024 x 1024 RGBA are 64 MiB; a 17th halves both sides.
+        assert_eq!(shared_size(sizes(16), 16, 64 << 20), Some((1024, 1024)));
+        assert_eq!(shared_size(sizes(17), 17, 64 << 20), Some((512, 512)));
+        // The largest of each side, never past MAX_SIDE.
+        let mixed = [(16, 4096), (64, 32)].into_iter();
+        assert_eq!(shared_size(mixed, 2, 64 << 20), Some((64, 1024)));
+        assert_eq!(shared_size(std::iter::empty(), 0, 64 << 20), None);
+    }
+
+    #[test]
+    fn blurred_glints_grow_smoothly_and_sharp_ones_by_texel() {
+        // Black then white, doubled: the wrapping blend of the two, or each texel twice.
+        let row = [0, 0, 0, 255, 255, 255, 255, 255];
+        let red = |rgba: Vec<u8>| rgba.chunks(4).map(|t| t[0]).collect::<Vec<_>>();
+        assert_eq!(red(resize(&row, (2, 1), (4, 1), true)), [64, 64, 191, 191]);
+        assert_eq!(red(resize(&row, (2, 1), (4, 1), false)), [0, 0, 255, 255]);
+    }
+
+    #[test]
+    fn a_layer_vertex_carries_its_slot_and_intensity() {
+        // Unorm8x4 reads the colour's bytes in memory order: r, g, b, a.
+        assert_eq!(vertex_color(3, 0.5).to_le_bytes(), [3, 0, 0, 128]);
+        assert_eq!(vertex_color(200, 2.0).to_le_bytes(), [200, 0, 0, 255]);
+        assert_eq!(vertex_color(0, -1.0).to_le_bytes(), [0, 0, 0, 0]);
+    }
+
+    #[test]
+    fn a_still_layer_is_scaled_and_turned() {
+        let close =
+            |a: [f32; 2], b: [f32; 2]| (a[0] - b[0]).abs() < 1e-5 && (a[1] - b[1]).abs() < 1e-5;
+        // No speed: no scroll whatever the clock.
+        assert!(close(
+            layer_uv([0.25, 0.5], 12_345.0, 0.0, 0.0, 8.0),
+            [2.0, 4.0]
+        ));
+        // A quarter turn takes (1, 0) to (0, 1).
+        assert!(close(layer_uv([1.0, 0.0], 0.0, 0.0, 90.0, 1.0), [0.0, 1.0]));
+        // 1500 ms at speed 2: 3000 / 110000 back, 3000 / 30000 up.
+        assert!(close(
+            layer_uv([0.0, 0.0], 1500.0, 2.0, 0.0, 8.0),
+            [-3.0 / 110.0, 0.1]
+        ));
+    }
+
+    #[test]
+    fn named_blends_take_their_gl_factors() {
+        let multiply = blend_state(parse_blend("multiply").unwrap());
+        assert_eq!(multiply.color.src_factor, wgpu::BlendFactor::Dst);
+        assert_eq!(
+            multiply.color.dst_factor,
+            wgpu::BlendFactor::OneMinusSrcAlpha
+        );
+        // The alpha factors default to GL_ZERO, GL_ONE: the target's alpha stays.
+        assert_eq!(multiply.alpha.src_factor, wgpu::BlendFactor::Zero);
+        assert_eq!(multiply.alpha.dst_factor, wgpu::BlendFactor::One);
+        assert_eq!(
+            blend_state(parse_blend("replace").unwrap()),
+            wgpu::BlendState::REPLACE
+        );
+    }
+}

crates/horizon-client-render/src/json_folder.rs

@@ -0,0 +1,154 @@
+//! A data folder's files read from the disk once while a load holds them.
+//! Several tables are built from the same folder (the recipes: the crafting
+//! tables, the stations, the recipe book, brewing), and each used to list and
+//! read every file again: on a hard disk or under a virus scanner, each open
+//! costs. The first reader lists and reads the folder; later readers share
+//! those bytes for as long as one of them holds the [`Folder`], then it is
+//! gone (nothing is kept past the load).
+use std::{
+    fs, io,
+    path::{Path, PathBuf},
+    sync::{Arc, Mutex, Weak},
+};
+
+/// One file: its path inside the folder without `.json` (`a/b`, as an id has
+/// it), the file, and its bytes or the error reading it gave.
+pub struct File {
+    pub name: String,
+    pub path: PathBuf,
+    bytes: Result<Box<[u8]>, (io::ErrorKind, String)>,
+}
+impl File {
+    pub fn bytes(&self) -> io::Result<&[u8]> {
+        self.bytes
+            .as_deref()
+            .map_err(|(kind, message)| io::Error::new(*kind, message.clone()))
+    }
+}
+
+/// Every `.json` file under a folder, its subfolders' too, in name order.
+pub struct Folder {
+    pub files: Vec<File>,
+}
+
+static OPEN: Mutex<Vec<(PathBuf, Weak<Folder>)>> = Mutex::new(Vec::new());
+
+fn find(open: &[(PathBuf, Weak<Folder>)], dir: &Path) -> Option<Arc<Folder>> {
+    open.iter()
+        .find(|(d, _)| d == dir)
+        .and_then(|(_, f)| f.upgrade())
+}
+
+/// `dir`'s files if another reader holds them, without reading anything.
+pub fn held(dir: &Path) -> Option<Arc<Folder>> {
+    find(&OPEN.lock().unwrap_or_else(|e| e.into_inner()), dir)
+}
+
+/// The `.json` files under `dir`: shared with any other reader holding them,
+/// else listed and read now. An error when `dir` itself can't be listed.
+pub fn read(dir: &Path) -> io::Result<Arc<Folder>> {
+    if let Some(folder) = held(dir) {
+        return Ok(folder);
+    }
+    let files = list(dir)?
+        .into_iter()
+        .map(|(name, path)| {
+            let bytes = fs::read(&path)
+                .map(Vec::into_boxed_slice)
+                .map_err(|e| (e.kind(), e.to_string()));
+            File { name, path, bytes }
+        })
+        .collect();
+    let folder = Arc::new(Folder { files });
+    let mut open = OPEN.lock().unwrap_or_else(|e| e.into_inner());
+    // Another reader may have read it meanwhile: share one copy.
+    if let Some(theirs) = find(&open, dir) {
+        return Ok(theirs);
+    }
+    open.retain(|(_, f)| f.strong_count() > 0);
+    open.push((dir.to_owned(), Arc::downgrade(&folder)));
+    Ok(folder)
+}
+
+/// The `.json` files under `dir` and its subfolders, in name order: each
+/// one's path inside the folder without the extension (`a/b`) and its file.
+/// An error when `dir` itself can't be listed; a subfolder or an entry that
+/// can't be is warned and skipped, as vanilla's `PathPackResources` keeps
+/// what it found.
+pub fn list(dir: &Path) -> io::Result<Vec<(String, PathBuf)>> {
+    let mut files = Vec::new();
+    let mut stack = vec![fs::read_dir(dir)?];
+    while let Some(entries) = stack.pop() {
+        for entry in entries {
+            let entry = match entry {
+                Ok(entry) => entry,
+                Err(e) => {
+                    log::warn!("Horizon: failed to list an entry of {}: {e}", dir.display());
+                    continue;
+                }
+            };
+            let path = entry.path();
+            if path.is_dir() {
+                match fs::read_dir(&path) {
+                    Ok(list) => stack.push(list),
+                    Err(e) => log::warn!("Horizon: failed to list {}: {e}", path.display()),
+                }
+            } else if path.extension().is_some_and(|e| e == "json") {
+                files.push(path);
+            }
+        }
+    }
+    let mut named: Vec<(String, PathBuf)> = files
+        .into_iter()
+        .map(|path| {
+            let inside = path.strip_prefix(dir).unwrap_or(&path).with_extension("");
+            let name: Vec<_> = inside.iter().map(|c| c.to_string_lossy()).collect();
+            (name.join("/"), path)
+        })
+        .collect();
+    // Vanilla lists resources by id, in a map keyed by it
+    // (`FallbackResourceManager`): `crushing` before `crushing/iron`, where
+    // a path's components put the subfolder's file first.
+    named.sort_by(|a, b| a.0.cmp(&b.0));
+    Ok(named)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn folder(tag: &str) -> PathBuf {
+        let dir =
+            std::env::temp_dir().join(format!("horizon-json-folder-{tag}-{}", std::process::id()));
+        let _ = fs::remove_dir_all(&dir);
+        fs::create_dir_all(dir.join("brewing")).unwrap();
+        fs::write(dir.join("stick.json"), b"{\"a\":1}").unwrap();
+        fs::write(dir.join("brewing/awkward.json"), b"{}").unwrap();
+        fs::write(dir.join("notes.txt"), b"not json").unwrap();
+        dir
+    }
+
+    #[test]
+    fn readers_share_the_bytes_while_one_holds_them_and_read_again_after() {
+        let dir = folder("share");
+        let first = read(&dir).unwrap();
+        let names: Vec<_> = first.files.iter().map(|f| f.name.as_str()).collect();
+        assert_eq!(names, ["brewing/awkward", "stick"]);
+        assert_eq!(first.files[1].bytes().unwrap(), b"{\"a\":1}");
+        // Held: a change on the disk isn't seen, the copy read is shared.
+        fs::write(dir.join("stick.json"), b"{\"a\":2}").unwrap();
+        let second = read(&dir).unwrap();
+        assert!(Arc::ptr_eq(&first, &second));
+        drop((first, second));
+        // Let go: the next reader reads the folder again.
+        assert_eq!(read(&dir).unwrap().files[1].bytes().unwrap(), b"{\"a\":2}");
+        fs::remove_dir_all(&dir).unwrap();
+    }
+
+    #[test]
+    fn a_folder_that_cannot_be_listed_is_an_error() {
+        let dir =
+            std::env::temp_dir().join(format!("horizon-json-folder-none-{}", std::process::id()));
+        assert!(read(&dir).is_err());
+    }
+}

crates/horizon-client-render/src/lib.rs

@@ -11,6 +11,7 @@ pub mod biome;
 pub mod block_edit;
 pub mod block_entities;
 pub mod block_entity_anim;
+pub mod block_entity_cem;
 pub mod block_entity_render;
 pub mod border_render;
 pub mod breaking;
@@ -20,7 +21,9 @@ pub mod chat;
 pub mod chunk;
 pub mod chunk_map;
 pub mod cit;
+pub mod cit_armor;
 pub mod cit_assets;
+pub mod cit_glint;
 pub mod clouds;
 pub mod collisions;
 pub mod command_block;
@@ -46,6 +49,7 @@ pub mod hud_overlays;
 pub mod inventory_effects;
 pub mod java_text;
 pub mod jigsaw_block;
+pub mod json_folder;
 pub mod level_loading;
 pub mod light;
 pub mod lod;

crates/horizon-client-render/src/mesher.rs

@@ -12,7 +12,7 @@ use crate::{
     assets::{Assets, RenderAssets},
     biome::Biomes,
     blocks::{BlockFacts, RenderShape},
-    chunk::{Chunk, MIN_Y},
+    chunk::{Chunk, Light, MIN_Y},
     graphics::LeafCullingMode,
     models::catalog::BakedFace,
 };
@@ -20,7 +20,7 @@ use horizon_assets::model::Direction as ModelDirection;
 use horizon_core::{
     biome::BiomeZoom, geometry::Direction, position::BlockPos, random::position_seed,
 };
-use horizon_optifine::ctm::connect::Face as CtmFace;
+use horizon_optifine::ctm::connect::{Axes as CtmAxes, Face as CtmFace};
 use horizon_world::{
     block_render::FaceVisibility,
     fluid::{FluidKind, FluidState},
@@ -283,7 +283,7 @@ impl SectionMesh {
     pub const BOUNDS_PAD: f32 = 0.5;
 
     /// Retain geometry capacity after an upload, but none of its old contents.
-    pub(crate) fn clear(&mut self) {
+    pub fn clear(&mut self) {
         self.solid.clear();
         self.translucent.clear();
         self.block_entities.clear();
@@ -505,6 +505,10 @@ pub struct MeshFacts {
 }
 pub struct MeshTables {
     info: Vec<Info>,
+    /// `Info::solid` by state, packed apart: the opacity mask of a section
+    /// reads 8,000 states, and a few bytes each stay in cache where `Info`
+    /// does not.
+    solid: Vec<bool>,
     pub visibility: FaceVisibility,
     water_still: u16,
     water_flow: u16,
@@ -673,6 +677,7 @@ impl MeshTables {
             });
         }
         Ok(Self {
+            solid: info.iter().map(|i| i.solid).collect(),
             info,
             visibility,
             water_still: layer("minecraft:block/water_still")?,
@@ -842,43 +847,66 @@ impl Padded {
     }
     fn fill(&mut self, region: &[[Option<&Chunk>; 3]; 3], sy: i32, own: &mut [u32; 4096]) {
         self.blocks.resize(P * P * P, 0);
-        self.blocks.fill(0);
         self.light.resize(P * P * P, 0);
         let (blocks, light) = (&mut self.blocks, &mut self.light);
         let base_y = region[1][1].map_or(MIN_Y, Chunk::min_y) + sy * 16;
-        // The section itself is unpacked in one pass; the border cells of the
-        // neighbouring sections are read one by one.
+        // The section itself is unpacked in one pass and copied row by row;
+        // the border cells of the neighbouring sections are read one by one,
+        // each run of them from a section found once.
         own.fill(0);
         let center = region[1][1].map(|c| &c.sections[sy as usize]);
         if let Some(section) = center {
             section.unpack(own);
         }
+        // The x runs of a padded row by the chunk column they fall in.
+        const RUNS: [(usize, i32, i32); 3] = [(0, -B, 0), (1, 0, 16), (2, 16, 16 + B)];
         for y in -B..16 + B {
             let wy = base_y + y;
             for z in -B..16 + B {
-                for x in -B..16 + B {
-                    let chunk = region[((z + 16) >> 4) as usize][((x + 16) >> 4) as usize];
-                    let i = pi(x, y, z);
-                    if let Some(c) = chunk {
-                        blocks[i] =
-                            if (0..16).contains(&x) && (0..16).contains(&y) && (0..16).contains(&z)
-                            {
-                                own[(y << 8 | z << 4 | x) as usize]
-                            } else {
-                                c.get(x & 15, wy, z & 15)
-                            };
-                        light[i] = c.light(x & 15, wy, z & 15);
-                    } else if let Some(c) = region[1][1] {
-                        // A neighbour not loaded continues this chunk's edge
-                        // column. As lit air, the outermost chunks' water drew
-                        // a wall toward it (fluids show both sides), a light
-                        // sheet in the water where far terrain carries on.
-                        // Vanilla draws no chunk without its neighbours.
-                        let (ex, ez) = (x.clamp(0, 15), z.clamp(0, 15));
-                        blocks[i] = c.get(ex, wy, ez);
-                        light[i] = c.light(ex, wy, ez);
+                let row = pi(-B, y, z);
+                let rz = ((z + 16) >> 4) as usize;
+                for (rx, x0, x1) in RUNS {
+                    let (start, end) = (row + (x0 + B) as usize, row + (x1 + B) as usize);
+                    let (blocks, light) = (&mut blocks[start..end], &mut light[start..end]);
+                    let Some(c) = region[rz][rx] else {
+                        match region[1][1] {
+                            // A neighbour not loaded continues this chunk's edge
+                            // column. As lit air, the outermost chunks' water drew
+                            // a wall toward it (fluids show both sides), a light
+                            // sheet in the water where far terrain carries on.
+                            // Vanilla draws no chunk without its neighbours.
+                            Some(c) => {
+                                let ez = z.clamp(0, 15);
+                                for (k, x) in (x0..x1).enumerate() {
+                                    let ex = x.clamp(0, 15);
+                                    blocks[k] = c.get(ex, wy, ez);
+                                    light[k] = c.light(ex, wy, ez);
+                                }
+                            }
+                            None => {
+                                blocks.fill(0);
+                                light.fill(0xF0);
+                            }
+                        }
+                        continue;
+                    };
+                    // `Chunk::get` and `Chunk::light` with the section found once.
+                    let s = (wy - c.min_y()) >> 4;
+                    let Some(section) = c.sections.get(s as usize).filter(|_| s >= 0) else {
+                        blocks.fill(0);
+                        light.fill(if s < 0 { 0 } else { 0xF0 });
+                        continue;
+                    };
+                    let at = crate::chunk::index(x0, wy, z);
+                    if rx == 1 && rz == 1 && (0..16).contains(&y) {
+                        let own_row = (y << 8 | z << 4) as usize;
+                        blocks.copy_from_slice(&own[own_row..own_row + 16]);
                     } else {
-                        light[i] = 0xF0;
+                        section.blocks.get_run(at, blocks);
+                    }
+                    match &section.light {
+                        Light::Uniform(v) => light.fill(*v),
+                        Light::Full(all) => light.copy_from_slice(&all[at..at + light.len()]),
                     }
                 }
             }
@@ -889,11 +917,33 @@ impl Padded {
 /// geometry still owned by the renderer, and total about 150 KiB per worker
 /// (the leaf mask adds 8,000 cells, depths and a queue).
 #[derive(Default)]
-pub(crate) struct MeshScratch {
+pub struct MeshScratch {
     padded: Padded,
     own: Option<Box<[u32; 4096]>>,
     visibility: Vec<usize>,
     leaf: leaf_culling::LeafMask,
+    /// Per padded row (`pi(-B, y, z) / P`), bit `x + B` set where the block
+    /// is `isSolidRender`.
+    opaque: Vec<u32>,
+}
+/// Fills `rows` with the padded section's opacity, one bit per block (`MeshScratch::opaque`).
+fn opaque_rows(pad: &Padded, solid: &[bool], rows: &mut Vec<u32>) {
+    rows.clear();
+    rows.extend(pad.blocks.as_chunks::<P>().0.iter().map(|row| {
+        row.iter().enumerate().fold(0u32, |bits, (x, &id)| {
+            bits | u32::from(solid[id as usize]) << x
+        })
+    }));
+}
+/// Whether the block at `(x, y, z)` (section-local) and its six neighbours
+/// are all `isSolidRender`: none of its faces can show.
+#[inline]
+fn hidden(rows: &[u32], x: i32, y: i32, z: i32) -> bool {
+    let row = |y: i32, z: i32| rows[((y + B) as usize) * P + (z + B) as usize];
+    let r = row(y, z);
+    let around =
+        r & r << 1 & r >> 1 & row(y - 1, z) & row(y + 1, z) & row(y, z - 1) & row(y, z + 1);
+    around >> (x + B) & 1 != 0
 }
 #[cfg(test)]
 mod leaf_culling_tests;
@@ -990,6 +1040,12 @@ enum Resolver {
 /// layer plus the blend radius around it, and the blended colours per column.
 struct Layer {
     zoomed: Vec<u16>,
+    /// Each resolver's colour of every cell of `zoomed`, filled on first use:
+    /// a cell is in the blend square of up to `(2r+1)^2` columns.
+    cells: [Vec<u32>; 4],
+    /// `BiomeZoom::corner_jitter` of the quart cells `zoomed` reaches, by
+    /// their offset from the first: each is shared by up to 16 cells of the layer.
+    jitter: Vec<Option<[[f64; 3]; 8]>>,
     colors: [[u32; 256]; 4],
 }
 /// `ClientLevel.calculateBlockTint` behind a per-layer `BlockTintCache`: each
@@ -1041,6 +1097,16 @@ impl<'a> Tints<'a> {
         [x, y, z]: [i32; 3],
     ) -> u16 {
         let q = zoom.quart_at_block(BlockPos::new(cx * 16 + x, base_y + y, cz * 16 + z));
+        Self::quart_biome(region, plains, [cx, cz], q)
+    }
+    /// The biome of quart cell `q` in the loaded chunks around chunk `(cx, cz)`, plains where
+    /// there is none.
+    fn quart_biome(
+        region: &[[Option<&Chunk>; 3]; 3],
+        plains: u16,
+        [cx, cz]: [i32; 2],
+        q: [i32; 3],
+    ) -> u16 {
         let (rx, rz) = ((q[0] >> 2) - cx + 1, (q[2] >> 2) - cz + 1);
         if (0..3).contains(&rx) && (0..3).contains(&rz) {
             region[rz as usize][rx as usize].map_or(plains, |c| {
@@ -1057,6 +1123,8 @@ impl<'a> Tints<'a> {
         let layer = self.layers[y as usize].get_or_insert_with(|| {
             Box::new(Layer {
                 zoomed: vec![NO_BIOME; dim * dim],
+                cells: Default::default(),
+                jitter: Vec::new(),
                 colors: [[UNSET; 256]; 4],
             })
         });
@@ -1065,21 +1133,45 @@ impl<'a> Tints<'a> {
         if cached != UNSET {
             return cached;
         }
-        let [cx, cz, _] = self.origin;
-        let (bx, bz) = (cx * 16, cz * 16);
+        let [cx, cz, base_y] = self.origin;
+        let (bx, by, bz) = (cx * 16, base_y + y, cz * 16);
         let (mut red, mut green, mut blue) = (0, 0, 0);
+        let cells = &mut layer.cells[resolver as usize];
+        if cells.is_empty() {
+            cells.resize(dim * dim, UNSET);
+        }
         for dz in -r..=r {
             for dx in -r..=r {
                 let cell = ((z + dz + r) as usize) * dim + (x + dx + r) as usize;
+                let known = cells[cell];
+                if known != UNSET {
+                    red += known >> 16 & 255;
+                    green += known >> 8 & 255;
+                    blue += known & 255;
+                    continue;
+                }
                 let mut biome = layer.zoomed[cell];
                 if biome == NO_BIOME {
-                    biome = Self::biome_id(
-                        &self.zoom,
-                        self.region,
-                        self.plains,
-                        self.origin,
-                        [x + dx, y, z + dz],
-                    );
+                    // BiomeManager.getBiome over the loaded chunks (plains
+                    // where there is none): `quart_at_block`, its cell's
+                    // corner jitter mixed once per layer.
+                    let block = BlockPos::new(bx + x + dx, by, bz + z + dz);
+                    let base = [block.x, block.y, block.z].map(|v| v.wrapping_sub(2) >> 2);
+                    let first = [bx - r, bz - r].map(|v| v.wrapping_sub(2) >> 2);
+                    let span = dim / 4 + 2;
+                    let at = (base[2] - first[1]) as usize * span + (base[0] - first[0]) as usize;
+                    if layer.jitter.is_empty() {
+                        layer.jitter.resize(span * span, None);
+                    }
+                    let jitter =
+                        layer.jitter[at].get_or_insert_with(|| self.zoom.corner_jitter(base));
+                    let corner = BiomeZoom::select_corner(block, jitter);
+                    let q = [
+                        base[0].wrapping_add((corner >> 2 & 1) as i32),
+                        base[1].wrapping_add((corner >> 1 & 1) as i32),
+                        base[2].wrapping_add((corner & 1) as i32),
+                    ];
+                    biome = Self::quart_biome(self.region, self.plains, [cx, cz], q);
                     layer.zoomed[cell] = biome;
                 }
                 let c = match resolver {
@@ -1091,6 +1183,7 @@ impl<'a> Tints<'a> {
                     Resolver::Dry => self.biomes.get(biome).dry_foliage,
                     Resolver::Water => self.biomes.get(biome).water,
                 };
+                cells[cell] = c;
                 red += c >> 16 & 255;
                 green += c >> 8 & 255;
                 blue += c & 255;
@@ -1144,7 +1237,9 @@ impl Mesher<'_> {
             &mut MeshScratch::default(),
         )
     }
-    pub(crate) fn mesh_reusing(
+    /// The meshing workers' path: `out`'s buffers and `scratch` are reused
+    /// rather than allocated per section.
+    pub fn mesh_reusing(
         &mut self,
         region: &[[Option<&Chunk>; 3]; 3],
         sy: i32,
@@ -1161,6 +1256,8 @@ impl Mesher<'_> {
         scratch.padded.fill(region, sy, own);
         let pad = &scratch.padded;
         out.visibility = visibility_reusing(pad, &self.tables.info, &mut scratch.visibility);
+        opaque_rows(pad, &self.tables.solid, &mut scratch.opaque);
+        let opaque = &scratch.opaque;
         let base_y = center.min_y() + sy * 16;
         if self.leaf_culling.is_interior() {
             scratch
@@ -1193,12 +1290,7 @@ impl Mesher<'_> {
                         out.lights
                             .push(([center.x * 16 + x, base_y + y, center.z * 16 + z], id));
                     }
-                    if state.solid
-                        && Direction::ALL.iter().all(|d| {
-                            let [dx, dy, dz] = d.normal();
-                            info[pad.blocks[pi(x + dx, y + dy, z + dz)] as usize].solid
-                        })
-                    {
+                    if hidden(opaque, x, y, z) {
                         continue;
                     }
                     if state.fluid.kind() != FluidKind::Empty {
@@ -1377,6 +1469,14 @@ impl Mesher<'_> {
                 [world.x, world.y, world.z],
                 |[dx, dy, dz]| pad.blocks[pi(pos[0] + dx, pos[1] + dy, pos[2] + dz)],
                 || Some(tints.biome(pos[0], pos[1], pos[2])),
+                // A pane's tiles are drawn with the cube's UVs (below), so that is its texture.
+                || {
+                    if state.pane {
+                        Some(CtmAxes::cube(CtmFace::ALL[q.facing as usize]))
+                    } else {
+                        CtmAxes::texture(&q.positions, &q.uv)
+                    }
+                },
                 |overlay| {
                     if let Some(slot) = overlays.get_mut(count) {
                         *slot = Some(overlay);

crates/horizon-client-render/src/mesher/sides.rs

@@ -103,6 +103,22 @@ impl Sides {
         }
     }
 
+    /// A sort with these parts' `ends` and `planes`, for tests.
+    #[cfg(test)]
+    pub(crate) fn from_parts(
+        ends: [u32; 14],
+        grouped: bool,
+        split: bool,
+        planes: [f32; 7],
+    ) -> Self {
+        Self {
+            ends,
+            grouped,
+            split,
+            planes,
+        }
+    }
+
     /// The number of solid quads the buckets hold.
     pub fn quads(&self) -> u32 {
         self.ends[13]
@@ -128,6 +144,26 @@ impl Sides {
         self.runs(seen, part, draw);
     }
 
+    /// How many quads `part` draws facing every way (`every`).
+    pub fn part_quads(&self, part: Part) -> u32 {
+        let mut quads = 0;
+        self.every(part, |_, count| quads += count);
+        quads
+    }
+
+    /// The facts `visible_from` reads, for the GPU to find the same runs
+    /// (gpu_lists.wgsl): the parts' ends, the planes' bits,
+    /// then 1 when grouped plus 2 when split.
+    pub fn gpu_row(&self) -> [u32; 22] {
+        let mut row = [0; 22];
+        row[..14].copy_from_slice(&self.ends);
+        for (to, plane) in row[14..21].iter_mut().zip(self.planes) {
+            *to = plane.to_bits();
+        }
+        row[21] = u32::from(self.grouped) | u32::from(self.split) << 1;
+        row
+    }
+
     /// The runs of `part`'s quads facing every way.
     pub fn every(&self, part: Part, draw: impl FnMut(u32, u32)) {
         self.runs(|_| true, part, draw);
@@ -210,6 +246,29 @@ pub fn sort(solid: &mut Vec<TerrainVertex>) -> Sides {
 
 /// `sort`, with all the opaque parts first when `grouped`.
 fn sort_parts(solid: &mut Vec<TerrainVertex>, grouped: bool) -> Sides {
+    SORT_SCRATCH.with_borrow_mut(|scratch| sort_with(solid, grouped, scratch))
+}
+
+/// `sort`'s buffers, kept by each meshing thread: a section's quads went
+/// through fresh vectors, and the sorted copy replaced the mesh's own
+/// (recycled) buffer.
+#[derive(Default)]
+struct SortScratch {
+    slots: Vec<u8>,
+    keys: Vec<u64>,
+    sorted: Vec<[TerrainVertex; 4]>,
+}
+thread_local! {
+    static SORT_SCRATCH: std::cell::RefCell<SortScratch> = Default::default();
+}
+
+/// `f32::total_cmp`'s order as an unsigned integer's.
+fn total_order_key(v: f32) -> u32 {
+    let bits = v.to_bits() as i32;
+    (bits ^ (((bits >> 31) as u32) >> 1) as i32) as u32 ^ 0x8000_0000
+}
+
+fn sort_with(solid: &mut Vec<TerrainVertex>, grouped: bool, scratch: &mut SortScratch) -> Sides {
     let (quads, rest) = solid.as_chunks::<4>();
     debug_assert!(rest.is_empty(), "solid vertices come in quads");
     let cutout = |q: &[TerrainVertex; 4]| q[0].layer & OPAQUE_LAYER == 0;
@@ -218,15 +277,14 @@ fn sort_parts(solid: &mut Vec<TerrainVertex>, grouped: bool) -> Sides {
         true => b + 7 * usize::from(cutout),
         false => b * 2 + usize::from(cutout),
     };
-    let slots: Vec<u8> = quads
-        .iter()
-        .map(|q| position(bucket(q), cutout(q)) as u8)
-        .collect();
+    let slots = &mut scratch.slots;
+    slots.clear();
+    slots.extend(quads.iter().map(|q| position(bucket(q), cutout(q)) as u8));
     let has_cutout = quads.iter().any(cutout);
     let mut counts = [0u32; 7];
     let mut slot_counts = [0u32; 14];
     let mut planes = [0f32; 7];
-    for (quad, &part) in quads.iter().zip(&slots) {
+    for (quad, &part) in quads.iter().zip(slots.iter()) {
         slot_counts[usize::from(part)] += 1;
         let b = slot(grouped, usize::from(part)).0;
         if let Bucket::Side(axis, positive) = BUCKETS[b] {
@@ -246,33 +304,34 @@ fn sort_parts(solid: &mut Vec<TerrainVertex>, grouped: bool) -> Sides {
         *end = total;
     }
     if has_cutout || counts.iter().filter(|&&c| c > 0).count() > 1 {
-        let mut next: [u32; 14] = std::array::from_fn(|s| slot_ends[s] - slot_counts[s]);
-        let mut sorted = vec![quads[0]; quads.len()];
-        for (quad, &part) in quads.iter().zip(&slots) {
-            let at = &mut next[usize::from(part)];
-            sorted[*at as usize] = *quad;
-            *at += 1;
-        }
-        if has_cutout {
-            let mut start = 0;
-            for (s, &end) in slot_ends.iter().enumerate() {
-                let end = end as usize;
-                let slice = &mut sorted[start..end];
-                if let Bucket::Side(axis, positive) = BUCKETS[slot(grouped, s).0] {
-                    slice.sort_by(|a, b| {
-                        let a = a[0].pos[axis];
-                        let b = b[0].pos[axis];
-                        if positive {
-                            b.total_cmp(&a)
-                        } else {
-                            a.total_cmp(&b)
+        // One integer key per quad: its part, then (cutout meshes, side
+        // buckets) its plane from the outside in, then its index, which keeps
+        // the order of equal quads as a stable sort does.
+        let keys = &mut scratch.keys;
+        keys.clear();
+        keys.extend(
+            quads
+                .iter()
+                .zip(slots.iter())
+                .enumerate()
+                .map(|(i, (quad, &part))| {
+                    let plane = match BUCKETS[slot(grouped, usize::from(part)).0] {
+                        Bucket::Side(axis, positive) if has_cutout => {
+                            let key = total_order_key(quad[0].pos[axis]);
+                            if positive { !key } else { key }
                         }
-                    });
-                }
-                start = end;
-            }
-        }
-        *solid = sorted.into_flattened();
+                        _ => 0,
+                    };
+                    u64::from(part) << 56 | u64::from(plane) << 24 | i as u64
+                }),
+        );
+        debug_assert!(quads.len() < 1 << 24);
+        keys.sort_unstable();
+        let sorted = &mut scratch.sorted;
+        sorted.clear();
+        sorted.extend(keys.iter().map(|&k| quads[(k & 0xFF_FFFF) as usize]));
+        solid.clear();
+        solid.extend_from_slice(sorted.as_flattened());
     }
     Sides {
         ends: slot_ends,
@@ -286,6 +345,74 @@ fn sort_parts(solid: &mut Vec<TerrainVertex>, grouped: bool) -> Sides {
 mod tests {
     use super::*;
 
+    /// The sort as it was before the integer keys: quads moved to their
+    /// parts in order, then a stable sort by plane in each side bucket.
+    fn reference(solid: &[TerrainVertex], grouped: bool) -> Vec<TerrainVertex> {
+        let quads = solid.as_chunks::<4>().0;
+        let has_cutout = quads.iter().any(|q| q[0].layer & OPAQUE_LAYER == 0);
+        let mut sorted = Vec::new();
+        for n in 0..14 {
+            let (b, cutout) = slot(grouped, n);
+            let mut part: Vec<[TerrainVertex; 4]> = quads
+                .iter()
+                .filter(|q| bucket(q) == b && (q[0].layer & OPAQUE_LAYER == 0) == cutout)
+                .copied()
+                .collect();
+            if let (Bucket::Side(axis, positive), true) = (BUCKETS[b], has_cutout) {
+                part.sort_by(|a, b| {
+                    let (a, b) = (a[0].pos[axis], b[0].pos[axis]);
+                    if positive {
+                        b.total_cmp(&a)
+                    } else {
+                        a.total_cmp(&b)
+                    }
+                });
+            }
+            sorted.extend(part);
+        }
+        sorted.into_flattened()
+    }
+
+    #[test]
+    fn integer_keys_sort_as_the_stable_sort_did() {
+        let mut state = 0x2545_F491_4F6C_DD1Du64;
+        let mut next = move || {
+            state ^= state << 13;
+            state ^= state >> 7;
+            state ^= state << 17;
+            state
+        };
+        for round in 0..100 {
+            let grouped = round % 2 == 1;
+            let mut solid = Vec::new();
+            for _ in 0..(next() % 300) {
+                let origin = [0, 1, 2].map(|_| (next() % 34) as f32 / 2.0 - 0.5);
+                // Some negative and signed-zero planes too.
+                let origin = if next() % 9 == 0 {
+                    origin.map(|v| -v)
+                } else {
+                    origin
+                };
+                let layer = if round % 3 == 0 {
+                    OPAQUE_LAYER
+                } else {
+                    (next() % 2) as u16 * OPAQUE_LAYER
+                };
+                let faces = cube(origin, layer);
+                let face = (next() % 6) as usize;
+                solid.extend_from_slice(&faces[face * 4..face * 4 + 4]);
+            }
+            let expected = reference(&solid, grouped);
+            let sides = sort_parts(&mut solid, grouped);
+            assert_eq!(
+                bytemuck::cast_slice::<_, u8>(&solid),
+                bytemuck::cast_slice::<_, u8>(&expected),
+                "round {round}"
+            );
+            assert_eq!(sides.quads() as usize * 4, solid.len());
+        }
+    }
+
     fn quad(corners: [[f32; 3]; 4], layer: u16) -> [TerrainVertex; 4] {
         corners.map(|p| TerrainVertex::new(p, [0.0; 2], layer, 0, 0))
     }

crates/horizon-client-render/src/native_emissive.rs

@@ -28,10 +28,18 @@ pub fn load(root: &Path, sprites: &mut Sprites) {
     }
 }
 
+/// A connected-texture tile's sprite name without `.png`: tiles outside `textures/` are named by
+/// their resource path (`Sprites::insert_file`, which only they use), block sprites by an id.
+fn tile_file(name: &str) -> Option<&str> {
+    name.strip_prefix("assets/")?;
+    name.strip_suffix(".png")
+}
+
 /// OptiFine's emissive overlays of the block sprites already loaded (what the terrain draws;
 /// items draw from the HUD atlas): for each
-/// `<ns>:block/<name>` whose `<name><suffix>.png` sits beside it, the overlay is loaded too and
-/// paired with it, first by name, at most [`MAX`] - [`NATIVE`] (native mods keep their share of
+/// `<ns>:block/<name>`, or connected-texture tile `assets/<ns>/.../<name>.png`, whose
+/// `<name><suffix>.png` sits beside it, the overlay is loaded too and paired with it, blocks
+/// first, then tiles, each by name, at most [`MAX`] - [`NATIVE`] (native mods keep their share of
 /// the table). A pack without such files adds nothing.
 pub fn load_optifine(root: &Path, sprites: &mut Sprites) -> Vec<(String, String)> {
     let suffix = horizon_optifine::emissive::suffix(root);
@@ -41,21 +49,34 @@ pub fn load_optifine(root: &Path, sprites: &mut Sprites) -> Vec<(String, String)
     for layer in sprites.layers.values() {
         *sharing.entry(*layer).or_default() += 1;
     }
-    let bases: Vec<String> = sprites
+    let mut bases: Vec<String> = sprites
         .layers
         .iter()
         .filter(|(name, layer)| {
             sharing[layer] == 1
-                && name
+                && (name
                     .split_once(':')
                     .is_some_and(|(_, p)| p.starts_with("block/") && !p.ends_with(&suffix))
+                    || tile_file(name).is_some_and(|stem| !stem.ends_with(&suffix)))
         })
         .map(|(name, _)| name.clone())
         .collect();
+    // Blocks before tiles: a pack's many tiles must not crowd vanilla blocks' overlays out.
+    bases.sort_by_key(|name| (tile_file(name).is_some(), name.clone()));
     let mut pairs = Vec::new();
     for base in bases {
-        let overlay = format!("{base}{suffix}");
-        let file = crate::atlas_sources::texture_path(root, &overlay, "textures");
+        // A tile is named by its file, a block sprite by its id.
+        let (overlay, file) = match tile_file(&base) {
+            Some(stem) => {
+                let overlay = format!("{stem}{suffix}.png");
+                (overlay.clone(), root.join(overlay))
+            }
+            None => {
+                let overlay = format!("{base}{suffix}");
+                let file = crate::atlas_sources::texture_path(root, &overlay, "textures");
+                (overlay, file)
+            }
+        };
         if !std::fs::metadata(&file).is_ok_and(|m| m.is_file()) {
             continue;
         }
@@ -71,7 +92,12 @@ pub fn load_optifine(root: &Path, sprites: &mut Sprites) -> Vec<(String, String)
             continue;
         }
         // A file that doesn't load would glow as the missing texture: no pair instead.
-        match sprites.try_insert(root, &overlay) {
+        let loaded = if overlay.starts_with("assets/") {
+            sprites.insert_file(root, &overlay)
+        } else {
+            sprites.try_insert(root, &overlay)
+        };
+        match loaded {
             Ok(_) => pairs.push((base, overlay)),
             Err(e) => log::warn!("Horizon: emissive overlay {overlay} skipped: {e}"),
         }
@@ -192,13 +218,40 @@ mod tests {
         let props = root.join("assets/minecraft/optifine/emissive.properties");
         std::fs::create_dir_all(props.parent().unwrap()).unwrap();
         std::fs::write(&props, "suffix.emissive=_glow").unwrap();
+        // Connected-texture tiles pair with the overlay beside them.
+        let tiles = root.join("assets/minecraft/optifine/ctm/lamp");
+        png(&tiles.join("0.png"), 230);
+        png(&tiles.join("0_glow.png"), 240);
+        png(&tiles.join("1.png"), 250);
+        // A tile outside `ctm/` (`tiles=~/glass/2`) is a tile all the same.
+        png(&root.join("assets/minecraft/optifine/glass/2.png"), 245);
+        png(
+            &root.join("assets/minecraft/optifine/glass/2_glow.png"),
+            246,
+        );
+        for tile in ["ctm/lamp/0", "ctm/lamp/1", "glass/2"] {
+            sprites
+                .insert_file(&root, &format!("assets/minecraft/optifine/{tile}.png"))
+                .unwrap();
+        }
         let pairs = load_optifine(&root, &mut sprites);
         assert_eq!(
             pairs,
-            [(
-                "minecraft:block/deepslate".into(),
-                "minecraft:block/deepslate_glow".into()
-            )]
+            // Blocks first, then tiles.
+            [
+                (
+                    "minecraft:block/deepslate".into(),
+                    "minecraft:block/deepslate_glow".into()
+                ),
+                (
+                    "assets/minecraft/optifine/ctm/lamp/0.png".into(),
+                    "assets/minecraft/optifine/ctm/lamp/0_glow.png".into()
+                ),
+                (
+                    "assets/minecraft/optifine/glass/2.png".into(),
+                    "assets/minecraft/optifine/glass/2_glow.png".into()
+                ),
+            ]
         );
         std::fs::remove_dir_all(&root).unwrap();
     }

crates/horizon-client-render/src/options_ui.rs

@@ -5345,6 +5345,61 @@ mod tests {
         assert!(ui.resource_error.is_none());
     }
 
+    /// The texts of an options page, as laid out in `code`'s language, and the keys it lacked.
+    fn page_texts(code: &str, pages: &[Page]) -> (Vec<String>, Vec<String>) {
+        let s = Settings::default();
+        lang::scoped(lang::Language::load(&[], code), || {
+            let mut texts = Vec::new();
+            for page in pages {
+                let mut ui = OptionsUi::default();
+                ui.show(*page);
+                for w in ui.layout(&s, 480.0, 4000.0).0 {
+                    match w.kind {
+                        WKind::Button { label: t, .. }
+                        | WKind::Slider { label: t, .. }
+                        | WKind::Text { text: t, .. } => texts.push(t.plain()),
+                        _ => {}
+                    }
+                }
+            }
+            texts
+        })
+    }
+
+    /// Horizon's own options pages said "Splitscreen...", "Hide block-break particles" and
+    /// "Hotbar: Previous Slot" in every language (#1927).
+    #[test]
+    fn horizon_option_pages_follow_the_language() {
+        let (texts, missed) = page_texts("de_de", &[Page::Horizon, Page::Extras, Page::PadBinds]);
+        for want in [
+            "Splitscreen …",
+            "Partikel",
+            "Blockpartikel weg: Aus",
+            "Weicher Chat: Aus",
+            "Nachrichtenmarkierung: An",
+            "Kanäle für UI-Töne: Aus",
+            "Schnellzugriffsleiste: Vorheriger Platz",
+            "Schnellzugriffsleiste: Nächster Platz",
+        ] {
+            assert!(texts.iter().any(|t| t == want), "{want:?} not in {texts:?}");
+        }
+        // Every key these pages ask for is in the table; vanilla's own keys (`options.*`,
+        // `key.*`: dotted ids without spaces) come from the prepared resources, which this
+        // language does not have.
+        let missed: Vec<_> = missed
+            .into_iter()
+            .filter(|k| k.starts_with("horizon.") || k.contains(' ') || !k.contains('.'))
+            .collect();
+        assert_eq!(missed, Vec::<String>::new());
+        let (texts, _) = page_texts("pl_pl", &[Page::Extras, Page::PadBinds]);
+        for want in [
+            "Ukryj cząstki bloków: Wył.",
+            "Pasek szybkiego wyboru: poprzednie pole",
+        ] {
+            assert!(texts.iter().any(|t| t == want), "{want:?} not in {texts:?}");
+        }
+    }
+
     #[test]
     fn classic_mods_page_toggles_mods_and_keeps_dev_and_invalid_entries_inactive() {
         let atlas = atlas();

crates/horizon-client-render/src/particles.rs

@@ -4093,6 +4093,47 @@ impl ParticleEngine {
         }
     }
 
+    /// The particles that `entries` name, as lights: where each is this frame, its entry's colour
+    /// as RGB and reach, and its alpha as the intensity.
+    pub fn lights(
+        &self,
+        entries: &[horizon_shader_api::manifest::ParticleLight],
+        partial: f32,
+    ) -> Vec<([f64; 3], u32, f32, f32)> {
+        let shining: Vec<(ParticleType, u32, f32)> = entries
+            .iter()
+            .flat_map(|e| {
+                let [r, g, b] = e.color.map(|c| (c.clamp(0.0, 1.0) * 255.0) as u32);
+                e.particles.iter().filter_map(move |name| {
+                    let name = if name.contains(':') {
+                        name.clone()
+                    } else {
+                        format!("minecraft:{name}")
+                    };
+                    Some((
+                        ParticleType::from_name(&name)?,
+                        r << 16 | g << 8 | b,
+                        e.reach,
+                    ))
+                })
+            })
+            .collect();
+        if shining.is_empty() {
+            return Vec::new();
+        }
+        let f = f64::from(partial);
+        self.particles
+            .iter()
+            .filter(|p| p.rgba[3] > 0.0)
+            .filter_map(|p| {
+                let (_, rgb, reach) = shining.iter().find(|(ty, ..)| *ty == p.ty)?;
+                let at =
+                    std::array::from_fn(|i| p.previous[i] + (p.position[i] - p.previous[i]) * f);
+                Some((at, *rgb, *reach, p.rgba[3].clamp(0.0, 1.0)))
+            })
+            .collect()
+    }
+
     /// Camera-facing quads (`QuadParticleRenderState.renderRotatedQuad`).
     pub fn render(
         &self,

crates/horizon-client-render/src/screen_draw.rs

@@ -133,6 +133,21 @@ pub fn text(out: &mut Vec<Draw>, text: Text, x: i32, y: i32, color: i32, shadow:
         });
     }
 }
+/// `graphics.text` on text the caller already styled, drawn as it is: a `§`
+/// in it stays a character, as `FormattedCharSequence.forward`
+/// (`StringDecomposer.iterate`, not `iterateFormatted`) draws it. An edit box
+/// builds its own sequence that way, so a `§` in its value shows.
+pub fn text_as_typed(out: &mut Vec<Draw>, text: Text, x: i32, y: i32, color: i32, shadow: bool) {
+    if (color as u32) >> 24 != 0 {
+        out.push(Draw::Text {
+            text,
+            x,
+            y,
+            color,
+            shadow,
+        });
+    }
+}
 
 /// `StringDecomposer.iterateFormatted`: the drawn characters of `contents`,
 /// with their index in it and their style; legacy `§` codes restyle what
@@ -186,6 +201,11 @@ impl Measure<'_> {
     pub fn width(&self, t: &Text) -> i32 {
         self.0.width_text(&t.resolve_legacy()) as i32
     }
+    /// `Font.width(FormattedCharSequence)` of a sequence drawn as it is: a
+    /// `§` in the text counts as the glyph it is drawn as.
+    pub fn width_drawn(&self, t: &Text) -> i32 {
+        self.0.width_drawn(t) as i32
+    }
     pub fn width_str(&self, s: &str) -> i32 {
         self.0.width(s) as i32
     }
@@ -864,8 +884,8 @@ impl TextField {
                 displayed.clone()
             };
             let t = styled(half, self.display);
-            let w = m.width(&t);
-            text(out, t, draw_x, ty, color, self.text_shadow);
+            let w = m.width_drawn(&t);
+            text_as_typed(out, t, draw_x, ty, color, self.text_shadow);
             draw_x += w + 1;
         }
         let insert = self.cursor < len || len >= self.max_length;
@@ -878,7 +898,7 @@ impl TextField {
         }
         if !displayed.is_empty() && on_screen && (rel_cursor as usize) < shown_len {
             let t = styled(sub(&displayed, rel_cursor as usize, shown_len), self.cursor);
-            text(out, t, draw_x, ty, color, self.text_shadow);
+            text_as_typed(out, t, draw_x, ty, color, self.text_shadow);
         }
         if let Some(hint) = &self.hint
             && displayed.is_empty()

crates/horizon-client-render/src/spans.rs

@@ -46,6 +46,30 @@ pub fn time<T>(name: &'static str, f: impl FnOnce() -> T) -> T {
     SPANS.with(|s| s.borrow_mut().push(Span { name, ms, cpu_ms }));
     out
 }
+/// Consecutive steps of one function timed as spans: each [`Laps::lap`] records the time since
+/// the previous one (or since [`laps`]) under its name. Nothing is read while spans are off.
+pub struct Laps(Option<(Instant, Option<Duration>)>);
+/// Start timing the steps of a function (see [`Laps`]).
+#[inline]
+pub fn laps() -> Laps {
+    Laps(enabled().then(|| (Instant::now(), thread_cpu())))
+}
+impl Laps {
+    /// Record the step that just ended under `name`, and start the next.
+    #[inline]
+    pub fn lap(&mut self, name: &'static str) {
+        let Some((started, cpu)) = &mut self.0 else {
+            return;
+        };
+        let (now, now_cpu) = (Instant::now(), thread_cpu());
+        let ms = (now - *started).as_secs_f32() * 1000.0;
+        let cpu_ms = now_cpu
+            .zip(*cpu)
+            .map_or(ms, |(end, start)| (end - start).as_secs_f32() * 1000.0);
+        SPANS.with(|s| s.borrow_mut().push(Span { name, ms, cpu_ms }));
+        (*started, *cpu) = (now, now_cpu);
+    }
+}
 /// The CPU time this thread has used, where the platform tells it: a tick
 /// with more wall time than CPU time waited (for a lock, or for a core on a
 /// busy machine).
@@ -92,6 +116,161 @@ pub fn describe(spans: &[Span]) -> String {
     list.join(", ")
 }
 
+/// The start's timeline: `HORIZON_STARTUP_TRACE=FILE` writes every named step of
+/// the start (resource tables, the renderer, the title, a world's open, a
+/// server's join, a dimension change) on whichever thread ran it, one Chrome
+/// trace event per line (`tools/startup_trace.py` reads it; wrapped in `[...]`,
+/// Perfetto opens it). Times are microseconds since the process started. Off,
+/// a step costs one relaxed load.
+pub mod startup {
+    use std::{
+        io::Write as _,
+        sync::{
+            Mutex, OnceLock,
+            atomic::{AtomicBool, AtomicU32, Ordering},
+        },
+        time::Instant,
+    };
+
+    static ON: AtomicBool = AtomicBool::new(false);
+    static SINK: OnceLock<Option<Mutex<std::fs::File>>> = OnceLock::new();
+    static ORIGIN: OnceLock<Instant> = OnceLock::new();
+    static NEXT_THREAD: AtomicU32 = AtomicU32::new(1);
+    thread_local! {
+        /// This thread's trace id, given (with its name) on its first event.
+        static THREAD: std::cell::Cell<u32> = const { std::cell::Cell::new(0) };
+    }
+
+    /// Opens the trace named by `HORIZON_STARTUP_TRACE`, timed from `origin`
+    /// (the process's start). Call once, first thing.
+    pub fn init(origin: Instant) {
+        ORIGIN.get_or_init(|| origin);
+        let sink = SINK.get_or_init(|| {
+            let path = std::env::var_os("HORIZON_STARTUP_TRACE")?;
+            std::fs::File::create(&path).ok().map(Mutex::new)
+        });
+        ON.store(sink.is_some(), Ordering::Relaxed);
+    }
+
+    /// Whether a trace is being written.
+    #[inline]
+    pub fn on() -> bool {
+        ON.load(Ordering::Relaxed)
+    }
+
+    fn micros(at: Instant) -> u128 {
+        ORIGIN.get().map_or(0, |origin| {
+            at.saturating_duration_since(*origin).as_micros()
+        })
+    }
+
+    fn write(event: std::fmt::Arguments) {
+        let Some(Some(sink)) = SINK.get() else {
+            return;
+        };
+        let tid = THREAD.with(|id| {
+            if id.get() == 0 {
+                id.set(NEXT_THREAD.fetch_add(1, Ordering::Relaxed));
+                let name = std::thread::current()
+                    .name()
+                    .unwrap_or("unnamed")
+                    .replace(['"', '\\'], "_");
+                let mut file = sink.lock().unwrap_or_else(std::sync::PoisonError::into_inner);
+                let _ = writeln!(
+                    file,
+                    r#"{{"ph":"M","name":"thread_name","pid":1,"tid":{},"args":{{"name":"{name}"}}}}"#,
+                    id.get()
+                );
+            }
+            id.get()
+        });
+        let mut file = sink
+            .lock()
+            .unwrap_or_else(std::sync::PoisonError::into_inner);
+        let _ = writeln!(file, r#"{{"pid":1,"tid":{tid},{event}}}"#);
+    }
+
+    /// A step running until it is dropped.
+    #[must_use = "the step ends when this is dropped"]
+    pub struct Step {
+        name: &'static str,
+        started: Instant,
+    }
+    impl Drop for Step {
+        fn drop(&mut self) {
+            let end = Instant::now();
+            write(format_args!(
+                r#""ph":"X","name":"{}","ts":{},"dur":{}"#,
+                self.name,
+                micros(self.started),
+                end.saturating_duration_since(self.started).as_micros()
+            ));
+        }
+    }
+
+    /// Starts a step named `name` (a literal: no quotes or backslashes).
+    #[inline]
+    pub fn step(name: &'static str) -> Option<Step> {
+        on().then(|| Step {
+            name,
+            started: Instant::now(),
+        })
+    }
+
+    /// Runs `f` as a step named `name`.
+    #[inline]
+    pub fn time<T>(name: &'static str, f: impl FnOnce() -> T) -> T {
+        let _step = step(name);
+        f()
+    }
+
+    /// A moment of the start: the title drawn, the world in view.
+    #[inline]
+    pub fn mark(name: &'static str) {
+        if on() {
+            write(format_args!(
+                r#""ph":"i","s":"g","name":"{name}","ts":{}"#,
+                micros(Instant::now())
+            ));
+        }
+    }
+
+    /// The first time `name` happens, as a mark. `once` is the caller's flag.
+    #[inline]
+    pub fn mark_once(once: &AtomicBool, name: &'static str) {
+        if on() && !once.swap(true, Ordering::Relaxed) {
+            mark(name);
+        }
+    }
+
+    /// Set while a world opens, a server is joined or the dimension changes,
+    /// until the view first fills ([`view_filled`]).
+    static FILLING: AtomicBool = AtomicBool::new(false);
+
+    /// A world starts loading: the next full view is marked.
+    pub fn arm(name: &'static str) {
+        if on() {
+            mark(name);
+            FILLING.store(true, Ordering::Relaxed);
+        }
+    }
+
+    /// Called each frame in a world: marks `world.view_full` the first frame
+    /// after [`arm`] where nothing waits to load, generate, light, mesh or
+    /// upload and the resident columns cover perf_bench's share of the view
+    /// (0.8 pi r^2: corners are never loaded).
+    #[inline]
+    pub fn view_filled(resident: usize, pending: usize, radius: u32) {
+        if FILLING.load(Ordering::Relaxed)
+            && pending == 0
+            && resident as f64 >= 0.8 * std::f64::consts::PI * f64::from(radius * radius)
+            && FILLING.swap(false, Ordering::Relaxed)
+        {
+            mark("world.view_full");
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::Span;
@@ -138,6 +317,25 @@ mod tests {
         assert!(super::take().is_empty());
     }
 
+    /// Laps record the steps between them while spans are on, and nothing while off.
+    #[test]
+    fn laps_time_consecutive_steps() {
+        let _ = super::take();
+        let mut off = super::laps();
+        off.lap("unseen");
+        super::enable(true);
+        let mut laps = super::laps();
+        std::thread::sleep(std::time::Duration::from_millis(2));
+        laps.lap("first");
+        laps.lap("second");
+        super::enable(false);
+        off.lap("still unseen");
+        let spans = super::take();
+        let names: Vec<_> = spans.iter().map(|s| s.name).collect();
+        assert_eq!(names, ["first", "second"]);
+        assert!(spans[0].ms >= 2.0);
+    }
+
     /// The thread's CPU clock moves with work done on it, not with time
     /// spent asleep.
     #[cfg(any(unix, all(windows, target_arch = "x86_64")))]

crates/horizon-client-render/src/sprites.rs

@@ -413,6 +413,119 @@ impl Sprites {
         };
         self.register(root, resource, decoded)
     }
+    /// The tiles of the texture `name` (`ns:path`) cut into a `columns` x `rows` grid, row by
+    /// row from the top left: a Fusion connecting texture's sheet. Each tile is its own layer
+    /// (named `fusion/<ns>/<path>#<tile>`); a fully transparent one is `None`, as Fusion skips
+    /// empty tiles. Tiles are square, as wide as a column. An animated sheet's frames are whole
+    /// grids one below the other, or with `per_tile` each cell is a column of its tile's frames.
+    /// The sheet's own layer, if models already show it, shows its first tile from then on.
+    pub fn insert_tiles(
+        &mut self,
+        root: &Path,
+        name: &str,
+        (columns, rows): (u32, u32),
+        per_tile: bool,
+    ) -> Result<Vec<Option<u32>>> {
+        let path = crate::atlas_sources::texture_path(root, name, "textures");
+        let metadata = match fs::read_to_string(path.with_extension("png.mcmeta")) {
+            Ok(text) => Some(serde_json::from_str::<
+                BTreeMap<String, Box<serde_json::value::RawValue>>,
+            >(&text)?),
+            Err(error) if error.kind() == std::io::ErrorKind::NotFound => None,
+            Err(error) => return Err(error.into()),
+        };
+        let animation = metadata
+            .as_ref()
+            .and_then(|m| m.get("animation"))
+            .map(|v| v.get().to_owned());
+        // The sheet's `texture` section is each tile's.
+        let texture = texture_section(metadata.as_ref());
+        let strategy = texture
+            .as_ref()
+            .and_then(|t| t["mipmap_strategy"].as_str())
+            .and_then(crate::mipmap::Strategy::parse)
+            .unwrap_or_default();
+        let alpha_cutoff_bias = texture
+            .as_ref()
+            .and_then(|t| t["alpha_cutoff_bias"].as_f64())
+            .unwrap_or(0.0) as f32;
+        let (width, height, pixels) = read_rgba(&path)?;
+        let side = width / columns.max(1);
+        // How far down the next frame of a tile is, and the next row of tiles.
+        let (frame_step, row_step) = match per_tile {
+            true => (side, height / rows.max(1)),
+            false => (rows * side, side),
+        };
+        let frames = match per_tile {
+            true => row_step / side.max(1),
+            false => height / frame_step.max(1),
+        };
+        let whole = match per_tile {
+            true => height % rows.max(1) == 0 && row_step % side.max(1) == 0,
+            false => height % frame_step.max(1) == 0,
+        };
+        if side == 0 || frames == 0 || width % columns.max(1) != 0 || !whole {
+            return Err(format!("{name} isn't a {columns} x {rows} grid of square tiles").into());
+        }
+        let tiles = (0..columns * rows)
+            .map(|tile| {
+                let frames: Vec<Vec<u8>> = (0..frames)
+                    .map(|f| {
+                        let (x, y) = (
+                            tile % columns * side,
+                            tile / columns * row_step + f * frame_step,
+                        );
+                        (y..y + side)
+                            .flat_map(|row| {
+                                let start = ((row * width + x) * 4) as usize;
+                                pixels[start..start + side as usize * 4].iter().copied()
+                            })
+                            .collect()
+                    })
+                    .collect();
+                let alphas = || frames.iter().flat_map(|f| f.iter().skip(3).step_by(4));
+                if alphas().all(|&a| a == 0) {
+                    return Ok(None);
+                }
+                let decoded = crate::sprite_cache::Decoded {
+                    side,
+                    animation: animation.clone().filter(|_| frames.len() > 1),
+                    strategy,
+                    alpha_cutoff_bias,
+                    has_transparent: alphas().any(|&a| a == 0),
+                    opaque: alphas().all(|&a| a == 255),
+                    translucent: alphas().any(|&a| a != 0 && a != 255),
+                    frames,
+                };
+                let tile_name = format!("fusion/{}#{tile}", name.replace(':', "/"));
+                self.register(root, &tile_name, decoded).map(Some)
+            })
+            .collect::<Result<Vec<_>>>()?;
+        // Where Fusion doesn't draw the sheet (items, other models), the lone tile rather than
+        // the whole sheet squeezed square, whose size would set every layer's.
+        if let (Some(&own), Some(&first)) = (self.layers.get(name), tiles.iter().flatten().next()) {
+            self.show_as(own, first);
+        }
+        Ok(tiles)
+    }
+    /// Layer `layer` shows what `source` does, and is no longer the layer of its old pixels.
+    fn show_as(&mut self, layer: u32, source: u32) {
+        self.still.retain(|_, l| *l != layer);
+        let (l, s) = (layer as usize, source as usize);
+        self.native[l] = self.native[s].clone();
+        self.opaque[l] = self.opaque[s];
+        self.translucent[l] = self.translucent[s];
+        self.mips[l] = self.mips[s];
+        self.pbr[l] = self.pbr[s].clone();
+        self.animations.retain(|a| a.layer != layer);
+        if let Some(animation) = self.animations.iter().find(|a| a.layer == source) {
+            let animation = SpriteAnimation {
+                layer,
+                ..animation.clone()
+            };
+            self.animations.push(animation);
+        }
+    }
     /// Read and decode one texture and its `.mcmeta`.
     fn decode(root: &Path, name: &str) -> Result<crate::sprite_cache::Decoded> {
         if !name.contains(':') {
@@ -762,6 +875,75 @@ mod tests {
         fs::remove_dir_all(&root).unwrap();
     }
     #[test]
+    fn tile_sheets_cut_into_a_layer_per_tile() {
+        let root =
+            std::env::temp_dir().join(format!("horizon-sprite-tiles-{}", std::process::id()));
+        let file = root.join("assets/minecraft/textures/block/sheet.png");
+        fs::create_dir_all(file.parent().unwrap()).unwrap();
+        // 3 columns of 2 x 2 tiles over 4 rows of pixels: the pixel at (x, y) has red x, green
+        // y; the middle column is transparent, and the top-right tile half see-through.
+        let (w, h) = (6u32, 4u32);
+        let pixels: Vec<u8> = (0..w * h)
+            .flat_map(|i| {
+                let (x, y) = (i % w, i / w);
+                let alpha = match x / 2 {
+                    1 => 0,
+                    2 if y < 2 => 128,
+                    _ => 255,
+                };
+                [x as u8, y as u8, 0, alpha]
+            })
+            .collect();
+        let mut encoder = png::Encoder::new(File::create(&file).unwrap(), w, h);
+        encoder.set_color(png::ColorType::Rgba);
+        encoder.set_depth(png::BitDepth::Eight);
+        encoder
+            .write_header()
+            .unwrap()
+            .write_image_data(&pixels)
+            .unwrap();
+        // Red and green of each pixel in a layer's frame.
+        let texels = |sprites: &Sprites, layer: u32, frame: usize| -> Vec<(u8, u8)> {
+            sprites.native[layer as usize].1[frame]
+                .chunks(4)
+                .map(|p| (p[0], p[1]))
+                .collect()
+        };
+        let mut sprites = Sprites::default();
+        let name = "minecraft:block/sheet";
+        let own = sprites.insert(&root, name).unwrap();
+        // Still, as a 3 x 2 grid: the empty middle column draws nothing.
+        let tiles = sprites.insert_tiles(&root, name, (3, 2), false).unwrap();
+        // The sheet's own layer now shows the top-left tile, at a tile's size.
+        assert_eq!(texels(&sprites, own, 0), [(0, 0), (1, 0), (0, 1), (1, 1)]);
+        assert_eq!(
+            tiles.iter().map(Option::is_some).collect::<Vec<_>>(),
+            [true, false, true, true, false, true]
+        );
+        let bottom_left = tiles[3].unwrap();
+        assert_eq!(
+            texels(&sprites, bottom_left, 0),
+            [(0, 2), (1, 2), (0, 3), (1, 3)]
+        );
+        assert!(sprites.translucent[tiles[2].unwrap() as usize]);
+        assert!(sprites.opaque[bottom_left as usize]);
+        // Animated, as one row of tiles: two frames, the grid's top and then its bottom half;
+        // per tile, each cell is the column of a tile's frames, which here is the same.
+        fs::write(file.with_extension("png.mcmeta"), r#"{"animation":{}}"#).unwrap();
+        for per_tile in [false, true] {
+            let mut sprites = Sprites::default();
+            let tiles = sprites.insert_tiles(&root, name, (3, 1), per_tile).unwrap();
+            let first = tiles[0].unwrap();
+            assert_eq!(texels(&sprites, first, 0), [(0, 0), (1, 0), (0, 1), (1, 1)]);
+            assert_eq!(texels(&sprites, first, 1), [(0, 2), (1, 2), (0, 3), (1, 3)]);
+            assert_eq!(sprites.animations.len(), 2, "two non-empty tiles");
+        }
+        // Not a grid of square tiles.
+        assert!(sprites.insert_tiles(&root, name, (4, 1), false).is_err());
+        assert!(sprites.insert_tiles(&root, name, (3, 3), false).is_err());
+        fs::remove_dir_all(&root).unwrap();
+    }
+    #[test]
     fn custom_item_texture_ids_load_with_their_animation() {
         let root = std::env::temp_dir().join(format!("horizon-sprite-cit-{}", std::process::id()));
         let file = root.join("assets/minecraft/optifine/cit/a.png");

crates/horizon-client-render/src/streaming.rs

@@ -1131,6 +1131,13 @@ impl Streaming {
         world
             .block_entities
             .load_chunk(std::mem::take(&mut chunk.block_entities));
+        if let Some(extras) = &chunk.saved {
+            for (pos, attachments) in &extras.block_entity_attachments {
+                world
+                    .block_entities
+                    .restore_attachments(*pos, attachments.clone());
+            }
+        }
         world
             .block_names
             .extend(std::mem::take(&mut chunk.block_names));

crates/horizon-client-render/src/telemetry.rs

@@ -20,9 +20,6 @@ const MIN_SECONDS: f32 = 60.0;
 const CRASH_DETAILS: [&str; 3] = ["Horizon Version", "Graphics Adapter", "Render Settings"];
 
 static STARTED: OnceLock<Instant> = OnceLock::new();
-/// When the menu bundle became ready, so the time to the title screen measures
-/// the menu and not the world bundle loaded behind it.
-static UI_READY_MS: AtomicU32 = AtomicU32::new(u32::MAX);
 static CORE_READY_MS: AtomicU32 = AtomicU32::new(u32::MAX);
 static REST_READY_MS: AtomicU32 = AtomicU32::new(u32::MAX);
 /// The GPU, once the renderer has its adapter: name, maker, kind, driver, backend, its own memory.
@@ -46,14 +43,6 @@ pub fn mark_start() {
     STARTED.get_or_init(Instant::now);
 }
 
-/// The menu bundle is ready: the title screen can draw. The first writer wins.
-pub fn mark_ui_ready() {
-    if let Some(started) = STARTED.get() {
-        let ms = started.elapsed().as_millis() as u32;
-        let _ = UI_READY_MS.compare_exchange(u32::MAX, ms, Ordering::Relaxed, Ordering::Relaxed);
-    }
-}
-
 pub fn mark_core_ready() {
     mark_ready(&CORE_READY_MS);
 }
@@ -241,17 +230,18 @@ impl Session {
     pub fn title_shown(&mut self) {
         if !self.title_measured {
             self.title_measured = true;
-            let ui_ms = UI_READY_MS.load(Ordering::Relaxed);
-            self.to_title_ms = if ui_ms != u32::MAX {
-                Some(ui_ms)
-            } else {
-                STARTED.get().map(|s| s.elapsed().as_millis() as u32)
-            };
+            crate::spans::startup::mark("title.shown");
+            // The frame itself: the menu bundle can be ready seconds before
+            // the renderer that draws it (pipelines compiling on a slow driver).
+            self.to_title_ms = STARTED.get().map(|s| s.elapsed().as_millis() as u32);
         }
     }
 
     /// A world starts loading.
     pub fn world_opening(&mut self) {
+        if self.opening.is_none() {
+            crate::spans::startup::arm("world.opening");
+        }
         self.opening.get_or_insert_with(Instant::now);
     }
 
@@ -262,10 +252,11 @@ impl Session {
 
     /// A frame drawn while playing (not in menus or loading).
     pub fn frame(&mut self, ms: f32) {
-        if let Some(opening) = self.opening.take()
-            && self.to_world_ms.is_none()
-        {
-            self.to_world_ms = Some(opening.elapsed().as_millis() as u32);
+        if let Some(opening) = self.opening.take() {
+            crate::spans::startup::mark("world.first_frame");
+            if self.to_world_ms.is_none() {
+                self.to_world_ms = Some(opening.elapsed().as_millis() as u32);
+            }
         }
         self.frames.record(ms);
         self.played_ms += ms;

crates/horizon-client-render/src/terrain.wgsl

@@ -37,6 +37,9 @@ struct Globals {
     // HDR output's tier windows (hdr.rs `Hdr::windows`): x..w low to very bright,
     // [0] where the lift starts, [1] where it is full.
     hdr_windows: array<vec4<f32>, 2>,
+    // HDR lighting: x how strongly the sky lights the world now (`Sky::sky_light_factor`),
+    // y what the sky and fog get: the same, but none under water.
+    hdr_light: vec4<f32>,
 }
 @group(0) @binding(0) var<uniform> globals: Globals;
 @group(0) @binding(1) var sprites: texture_2d_array<f32>;
@@ -171,6 +174,8 @@ struct TerrainOut {
     // How the face shines in HDR output (mesher.rs's `EMISSION_BITS`): 0 not
     // at all, 1 to 4 the tier with its bright parts, 5 to 8 the tier all over.
     @location(5) @interpolate(flat) emission: u32,
+    // HDR lighting: block and sky light, as levels 0 to 15.
+    @location(11) scene: vec2<f32>,
     @location(6) @interpolate(flat) fade: u32,
     // A distant tile's tile-relative position, for its fade (`faded`).
     @location(7) local: vec3<f32>,
@@ -361,6 +366,22 @@ fn left_out() -> TerrainOut {
     return terrain_vertex(position, terrain_uv(uv, origin.w), layer, color, light, origin.xyz,
         origin.w);
 }
+// HDR lighting: how far a surface's light carries it above paper white, 0 to 1. Only the
+// strongest light does, so dark stays as dark as in SDR; sky light by how the face meets the sun.
+fn hdr_scene(block: f32, sky: f32, facing: f32) -> f32 {
+    let b = smoothstep(11.0, 15.0, block);
+    let s = smoothstep(11.0, 15.0, sky) * globals.hdr_light.x * facing;
+    return max(b, s);
+}
+// The frame's alpha for it, between 1 (none) and the light sources' marks below 0.75.
+fn hdr_scene_alpha(scene: f32) -> f32 {
+    return 1.0 - 0.24 * scene;
+}
+// The face's normal, from the fragment's derivatives, for how it faces the sun.
+var<private> hdr_normal: vec3<f32>;
+fn hdr_facing() -> f32 {
+    return mix(0.45, 1.0, max(dot(hdr_normal, globals.sun.xyz), 0.0));
+}
 fn terrain_vertex(position: vec3<f32>, uv: vec2<f32>, layer: u32, color: vec4<f32>,
     light: vec2<u32>, origin: vec3<f32>, w: f32) -> TerrainOut {
     let pos = position + origin;
@@ -384,6 +405,7 @@ fn terrain_vertex(position: vec3<f32>, uv: vec2<f32>, layer: u32, color: vec4<f3
     }
     let block = max(f32(light.y), dynamic_block_light(pos));
     out.color = vec4(color.rgb, 1.0) * sample_lightmap(f32(light.x) / 16.0, block / 16.0);
+    out.scene = vec2(block / 16.0, f32(light.x) / 16.0);
     if globals.colored_count.x > 0u {
         out.color = vec4(min(out.color.rgb + color.rgb * native_colored_light(pos), vec3(1.0)), out.color.a);
     }
@@ -426,6 +448,7 @@ fn hdr_mark(tier: u32, y: f32) -> f32 {
 }
 // `fs_solid` for the opaque pass (`opaque_quad`): no fade, no cutout, no discard.
 @fragment fn fs_opaque(in: TerrainOut) -> @location(0) vec4<f32> {
+    hdr_normal = normalize(cross(dpdy(in.local), dpdx(in.local)));
     let texel = sprite(in.uv, in.layer & 0x7fffu);
     var color = texel * in.color;
     color = mix(globals.fog_color * vec4(1.0, 1.0, 1.0, color.a), color, in.visibility);
@@ -440,6 +463,7 @@ fn hdr_mark(tier: u32, y: f32) -> f32 {
 fn solid_color(in: TerrainOut) -> vec4<f32> {
     let dx = dpdx(in.local);
     let dy = dpdy(in.local);
+    hdr_normal = normalize(cross(dy, dx));
     if faded(in.fade, in.local, dx, dy) { discard; }
     // Bit 15 of the layer marks opaque leaves (forceOpaque): no alpha cutout.
     let texel = sprite(in.uv, in.layer & 0x7fffu);
@@ -456,15 +480,24 @@ fn solid_finish(in: TerrainOut, texel: vec4<f32>, color: vec4<f32>) -> vec4<f32>
     // texel's own brightness, so its light level and face shading don't change
     // it. Only pixels as bright as their sprite's threshold may: its bright
     // parts, or all of it. Nothing else reads the frame's alpha.
-    var emissive = 1.0;
+    // Fog turns a far surface into the fog's colour: it takes the fog's light with it, or a
+    // fully fogged mountain would stand out from the fog behind it.
+    let fogged = max(linear_fog(in.spherical, globals.fog.x, globals.fog.y),
+        linear_fog(in.cylindrical, globals.fog.z, globals.fog.w)) * globals.fog_color.a;
+    var emissive = hdr_scene_alpha(mix(hdr_scene(in.scene.x, in.scene.y, hdr_facing()),
+        globals.hdr_light.y, fogged));
     if in.emission > 0u {
+        // A light source's own face shines as one or stays as drawn, without the lighting.
+        emissive = 1.0;
         let whole = in.emission > 4u;
         let tier = select(in.emission, in.emission - 4u, whole);
         let l = in.layer & 0x7fffu;
         let t = textureLoad(emission_thresholds, vec2(i32(l % SPRITE_SPLIT), i32(l / SPRITE_SPLIT)), 0);
         let y = brightness(texel.rgb);
-        if y >= select(t.r, t.g, whole) {
-            emissive = hdr_mark(tier, y);
+        // All over means all over: the sprite's range is one frame's, and an animated sprite's
+        // other frames dip below it. Fog hides a light source as it hides everything else.
+        if whole || y >= t.r {
+            emissive = hdr_mark(tier, y * (1.0 - fogged));
         }
     }
     if in.emissive_layer != 0xffffffffu {
@@ -612,7 +645,8 @@ fn sky_along_ray(d: vec3<f32>) -> vec3<f32> {
     return color;
 }
 @fragment fn fs_sky(in: SkyOut) -> @location(0) vec4<f32> {
-    return vec4(sky_along_ray(view_ray(in.ndc)), 1.0);
+    // `hdr_scene_alpha`, spelled out: this part of the file also goes into shader packs' skies.
+    return vec4(sky_along_ray(view_ray(in.ndc)), 1.0 - 0.24 * globals.hdr_light.y);
 }
 // The first-person hand's depth clear inside the world pass: `vs_sky`'s triangle lies at the
 // far plane, written over the whole depth target with no colour.

crates/horizon-client-render/src/ui.rs

@@ -384,19 +384,42 @@ pub fn scrolling_text_at(
     y: f32,
     now_ms: i64,
     color: u32,
+) {
+    // `acceptScrollingWithDefaultCenter`: `centerX = (left + right) / 2`.
+    let center_x = left + ((right - left) / 2.0).floor();
+    scrolling_text_around_at(
+        batch, atlas, text, center_x, left, right, top, bottom, y, now_ms, color,
+    );
+}
+
+/// [`scrolling_text_at`] around an explicit `center_x`
+/// (`ActiveTextCollector.acceptScrolling`, which `SpriteIconButton.TextAndIcon`
+/// calls with the button's middle): a label that fits is centred on `center_x`
+/// moved as far as it must to stay between `left` and `right`
+/// (`Mth.clamp(centerX, left + lineWidth / 2, right - lineWidth / 2)`), so
+/// beside an icon it ends where the icon's room begins. A wider one is drawn
+/// from the left and slid inside the box.
+#[allow(clippy::too_many_arguments)]
+pub fn scrolling_text_around_at(
+    batch: &mut HudBatch,
+    atlas: &HudAtlas,
+    text: &Text,
+    center_x: f32,
+    left: f32,
+    right: f32,
+    top: f32,
+    bottom: f32,
+    y: f32,
+    now_ms: i64,
+    color: u32,
 ) {
     let text = text.resolved();
     let width = atlas.font.width_text(&text);
     let room = right - left;
     if width <= room {
-        batch.text_styled(
-            atlas,
-            &text,
-            centered_left(left, room, width),
-            y,
-            color,
-            true,
-        );
+        let half = (width / 2.0).floor();
+        let text_x = center_x.max(left + half).min(right - half);
+        batch.text_styled(atlas, &text, text_x - half, y, color, true);
         return;
     }
     // Scissored to the widget: what does not fit is read as the label
@@ -440,6 +463,37 @@ pub fn scrolling_text(
     );
 }
 
+/// `MenuTabBar.MenuTabButton.renderLabel` for the tab at `x, y`: its label
+/// inside the tab less 1 px on each side, from the tab's top when selected
+/// and 3 px lower when not (`acceptScrollingWithDefaultCenter`, so one wider
+/// than the tab slides instead of running into the next tab). White, gray
+/// for an inactive tab (`WithInactiveMessage`).
+pub fn menu_tab_label(
+    batch: &mut HudBatch,
+    atlas: &HudAtlas,
+    label: &Text,
+    (x, y, width, height): (f32, f32, f32, f32),
+    selected: bool,
+    active: bool,
+    now_ms: i64,
+) {
+    let top = y + if selected { 0.0 } else { 3.0 };
+    let bottom = y + height;
+    scrolling_text_at(
+        batch,
+        atlas,
+        label,
+        x + 1.0,
+        x + width - 1.0,
+        top,
+        bottom,
+        // defaultScrollingHelper: `(top + bottom - lineHeight) / 2 + 1`.
+        ((top + bottom - 9.0) / 2.0).floor() + 1.0,
+        now_ms,
+        if active { u32::MAX } else { 0xFFA0_A0A0 },
+    );
+}
+
 /// Button (AbstractButton): nine-slice sprite plus the centred label.
 pub fn button(
     batch: &mut HudBatch,
@@ -1642,6 +1696,51 @@ mod tests {
         );
     }
 
+    /// `MenuTabButton.renderLabel` on a 24 px tab: centred on the tab, its
+    /// text top at `(0 + 24 - 9) / 2 + 1 = 8` when selected and at
+    /// `(3 + 24 - 9) / 2 + 1 = 10` when not; white on an active tab, selected
+    /// or not, `0xA0A0A0` on an inactive one (`WithInactiveMessage`). The
+    /// Statistics tabs drew every label at 8 and an active unselected one gray.
+    #[test]
+    fn a_tab_label_sits_lower_on_an_unselected_tab_and_is_gray_only_when_inactive() {
+        let atlas = atlas();
+        let label = Text::literal("Items");
+        let half = (atlas.font.width_text(&label.resolved()) / 2.0).floor();
+        // A 124 px tab at x = 100: `(left + right) / 2 = (101 + 223) / 2 = 162`.
+        let left = 162.0 - half;
+        for (selected, active, y, color) in [
+            (true, true, 8.0, u32::MAX),
+            (false, true, 10.0, u32::MAX),
+            (false, false, 10.0, 0xFFA0_A0A0),
+        ] {
+            let mut tab = HudBatch::new([640, 480]);
+            menu_tab_label(
+                &mut tab,
+                &atlas,
+                &label,
+                (100.0, 0.0, 124.0, 24.0),
+                selected,
+                active,
+                0,
+            );
+            let mut want = HudBatch::new([640, 480]);
+            want.text_styled(&atlas, &label.resolved(), left, y, color, true);
+            let glyphs = |b: &HudBatch| -> Vec<([u32; 2], u32)> {
+                b.vertices
+                    .iter()
+                    .filter(|v| v.text == 1)
+                    .map(|v| ([v.pos[0].to_bits(), v.pos[1].to_bits()], v.color))
+                    .collect()
+            };
+            assert!(!glyphs(&want).is_empty());
+            assert_eq!(
+                glyphs(&tab),
+                glyphs(&want),
+                "selected {selected}, active {active}"
+            );
+        }
+    }
+
     #[test]
     fn slider_track_is_outlined_only_while_dragged() {
         let (track, handle) = slider_sprites(true, true, false);

crates/horizon-client-render/src/world.rs

@@ -52,6 +52,8 @@ impl DirtySections {
     }
 }
 pub struct World {
+    /// Server-owned mod data attached to this dimension.
+    pub attachments: horizon_world::attachments::Attachments,
     /// The level's build range and skylight (its dimension type); its
     /// chunks hold `shape.column()`.
     pub shape: LevelShape,
@@ -200,6 +202,7 @@ impl World {
             loaded_entities: Vec::new(),
             loaded_chunks: Vec::new(),
             modified: FxHashSet::default(),
+            attachments: Default::default(),
             block_entities: Default::default(),
             chest_openers: FxHashMap::default(),
             block_names: FxHashMap::default(),

crates/horizon-client/assets/horizon/lang/de_de.json

@@ -95,6 +95,7 @@
   "UI Brightness": "GUI-Helligkeit",
   "Battery Mode": "Akkumodus",
   "Graphics API": "Grafik-API",
+  "Translucent Batching": "Transparenz-Batching",
   "Performance Overlay": "Leistungsanzeige",
   "Full Detail Distance": "Detailweite",
   "On": "An",
@@ -142,14 +143,12 @@
   "This feature is not yet available in Horizon.": "Diese Funktion ist in Horizon noch nicht verfügbar.",
   "Your display or system doesn't offer HDR output.": "Dein Bildschirm oder System unterstützt keine HDR-Ausgabe.",
   "Turn HDR on to use it.": "Schalte HDR ein, um es zu nutzen.",
+  "Your GPU or graphics API doesn't support it.": "Deine GPU oder Grafik-API unterstützt das nicht.",
   "%s chunks": "%s Chunks",
   "%s per frame": "%s pro Bild",
   "%s MiB/frame": "%s MiB/Bild",
   "%s KiB/frame": "%s KiB/Bild",
-  "%s nits": "%s Nits",
   "Auto (%s)": "Auto (%s)",
-  "Auto (%s nits)": "Auto (%s Nits)",
-  "%.2f nits": "%.2f Nits",
   "Full-detail terrain range. LOD Distance can extend local worlds farther.": "Gelände mit vollen Details. Die LOD-Entfernung reicht weiter.",
   "Coarse distant terrain in local worlds. Integrated GPUs stop at 128 chunks.": "Grobes fernes Gelände in lokalen Welten. Integrierte GPUs: max. 128.",
   "Reduced draws far terrain coarser: faster on this integrated GPU.": "Reduziert: fernes Gelände gröber, schneller auf dieser GPU.",
@@ -167,7 +166,6 @@
   "How far mobs, crops and machines keep working. CPU time.": "Wie weit Kreaturen, Pflanzen und Maschinen weiterarbeiten. Kostet CPU-Zeit.",
   "How far away mobs and items are drawn, as a share of normal.": "Zeichenweite für Kreaturen und Gegenstände, anteilig zur Norm.",
   "Skips terrain hidden behind closed sections. Off costs a lot.": "Überspringt Gelände hinter geschlossenen Abschnitten. Aus kostet viel.",
-  "Hides models behind opaque blocks. Entities update. Off with custom packs.": "Versteckt Modelle hinter Blöcken. Bei eigenen Paketen ausschalten.",
   "Meshed sections uploaded per frame. Lower is smoother while loading.": "Mesh-Abschnitte pro Bild. Weniger: flüssigeres Laden.",
   "Soft shadows in corners. Costs chunk building time only.": "Weiche Schatten in Ecken. Kostet nur Zeit beim Chunk-Aufbau.",
   "Smaller copies of block textures for distant terrain: less shimmer.": "Kleinere Textur-Kopien für fernes Gelände: weniger Flimmern.",
@@ -201,6 +199,7 @@
   "60 FPS cap (30 in menus or unfocused), half the workers: less power.": "60 FPS (30 im Menü/ohne Fokus), halb so viele Worker: spart Strom.",
   "Threads that generate, light and mesh chunks. Next start.": "Threads für Erzeugung, Licht und Mesh der Chunks. Nach Neustart.",
   "Vulkan, then DirectX 12 (Windows) or OpenGL (Linux) where it fails. Next start.": "Vulkan, sonst DirectX 12 (Windows) oder OpenGL (Linux). Nach Neustart.",
+  "Water and glass in one buffer: fewer draw calls, a bit more VRAM. Next start.": "Wasser und Glas in einem Puffer: weniger Draw-Calls, etwas mehr VRAM. Nach Neustart.",
   "Mesh data sent to the GPU per frame. Lower is smoother while loading.": "Pro Bild an die GPU gesendete Mesh-Daten. Weniger ist flüssiger beim Laden.",
   "Frame rate and frame times over the game, with a graph.": "Bildrate und Bildzeiten über dem Spiel, mit Diagramm.",
   "horizon.multiplayer.finding_friend": "Die Welt deines Freundes wird gesucht …",
@@ -289,5 +288,53 @@
   "horizon.multiplayer.not_signed_in": "Dieser Server läuft im Online-Modus. Melde dich im Horizon-Launcher mit deinem Microsoft-Konto an, um ihm beizutreten.",
   "horizon.multiplayer.invalid_address": "Ungültige Serveradresse: %s",
   "horizon.multiplayer.connected_friend_direct": "Direkt mit deinem Freund verbunden …",
-  "horizon.multiplayer.connected_friend_relay": "Über das Relay mit deinem Freund verbunden …"
+  "horizon.multiplayer.connected_friend_relay": "Über das Relay mit deinem Freund verbunden …",
+  "Culling": "Culling",
+  "Hides models behind opaque blocks. Async checks off-thread; entities tick.": "Versteckt Modelle hinter Blöcken. Prüfung im Hintergrund; Objekte laufen weiter.",
+  "Leaf Culling": "Laub-Culling",
+  "Every leaf face. Vanilla's fancy leaves.": "Jede Blattfläche, wie Minecraft sie bei schönen Blättern zeichnet.",
+  "Distant Plant Dither": "Pflanzen-Dithering",
+  "Keeps fine plants in high-res packs from fading far away.": "Verhindert, dass feine Pflanzen in hochauflösenden Paketen in der Ferne verblassen.",
+  "Screenshot Quality": "Screenshot-Qualität",
+  "F2 screenshots at this many times the game's resolution. Higher takes longer.": "F2-Screenshots in diesem Vielfachen der Spielauflösung. Höher dauert länger.",
+  "Frame Generation": "Bildgenerierung",
+  "Shows a made-up frame between each two real ones: smoother, a little more lag.": "Zeigt zwischen zwei echten Bildern ein errechnetes: flüssiger, etwas mehr Verzögerung.",
+  "Shadow Cache": "Schatten-Cache",
+  "Reuses the pack shadow map when sun, view and world match. Off by default.": "Verwendet die Schattenkarte des Pakets erneut, wenn Sonne, Blick und Welt gleich bleiben. Standardmäßig aus.",
+  "Synchronous": "Synchron",
+  "Asynchronous": "Asynchron",
+  "Solid": "Massiv",
+  "Solid Aggressive": "Massiv, aggressiv",
+  "Hollow": "Hohl",
+  "Leaves fully inside a canopy draw solid: fewer see-through layers.": "Blätter mitten im Blätterdach werden massiv gezeichnet: weniger durchsichtige Schichten.",
+  "Leaves with one open side draw solid too: faster, chunkier edges.": "Auch Blätter mit einer offenen Seite werden massiv gezeichnet: schneller, gröbere Kanten.",
+  "Drops faces between leaves: faster, but gaps look through.": "Lässt Flächen zwischen Blättern weg: schneller, aber Lücken sind durchsichtig.",
+  "Hotbar: Previous Slot": "Schnellzugriffsleiste: Vorheriger Platz",
+  "Hotbar: Next Slot": "Schnellzugriffsleiste: Nächster Platz",
+  "horizon.agent.connected.one": "Verbunden: 1 Agentenverbindung",
+  "horizon.agent.connected.many": "Verbunden: %s Agentenverbindungen",
+  "horizon.agent.connected.one_ago": "Verbunden: 1 Agentenverbindung, letzter Befehl vor %s s",
+  "horizon.agent.connected.many_ago": "Verbunden: %s Agentenverbindungen, letzter Befehl vor %s s",
+  "horizon.agent.waiting": "Wartet auf einen Agenten.",
+  "horizon.agent.off": "Aus: Agenten können dieses Spiel nicht erreichen.",
+  "horizon.agent.session_opened": "Für diese Sitzung von dem Programm geöffnet, das das Spiel gestartet hat.",
+  "horizon.agent.socket": "Socket: %s (Verbindungsdaten kopieren für den vollständigen Pfad)",
+  "horizon.agent.local_only": "Nur lokal: Agenten auf diesem Computer, nie über das Netzwerk.",
+  "horizon.extras.chat_animation": "Weicher Chat",
+  "horizon.extras.chat_animation.tooltip": "Eine neue Chatzeile gleitet von links herein und blendet dabei ein, statt sofort ganz zu erscheinen.",
+  "horizon.extras.chat_indicator": "Nachrichtenmarkierung",
+  "horizon.extras.chat_indicator.tooltip": "Der farbige Balken links neben einer Chatzeile.",
+  "horizon.extras.header.chat": "Chat",
+  "horizon.extras.header.particles": "Partikel",
+  "horizon.extras.header.sound": "Ton",
+  "horizon.extras.hide_block_particles": "Blockpartikel weg",
+  "horizon.extras.hide_block_particles.tooltip": "Blendet die Trümmerpartikel aus, die aus einem zerstörten Block sprühen und von dem abbröckeln, den du abbaust. Andere Partikel bleiben.",
+  "horizon.extras.splitscreen": "Splitscreen",
+  "horizon.extras.splitscreen.tooltip": "In einer Welt kann ein weiterer Controller als neuer Spieler beitreten: A drücken, wenn gefragt, dann Profil und Spielort wählen.",
+  "horizon.extras.ui_sound_reserve": "Kanäle für UI-Töne",
+  "horizon.extras.ui_sound_reserve.tooltip": "Weltgeräusche lassen 16 der 247 Tonkanäle frei, damit eine Flut davon (eine große Explosion) Menü-Klicks nicht verstummen lässt.",
+  "horizon.pages.open.split_setup": "Splitscreen …",
+  "horizon.pages.split_settings": "Splitscreen-Einstellungen",
+  "horizon.pages.split_setup": "Splitscreen",
+  "horizon.pages.split_setup.tooltip": "Spieler an diesem Computer: Controller können deiner Welt beitreten."
 }

crates/horizon-client/assets/horizon/lang/en_us.json

@@ -152,10 +152,7 @@
   "%s per frame": "%s per frame",
   "%s MiB/frame": "%s MiB/frame",
   "%s KiB/frame": "%s KiB/frame",
-  "%s nits": "%s nits",
   "Auto (%s)": "Auto (%s)",
-  "Auto (%s nits)": "Auto (%s nits)",
-  "%.2f nits": "%.2f nits",
   "Full-detail terrain range. LOD Distance can extend local worlds farther.": "Full-detail terrain range. LOD Distance can extend local worlds farther.",
   "Coarse distant terrain in local worlds. Integrated GPUs stop at 128 chunks.": "Coarse distant terrain in local worlds. Integrated GPUs stop at 128 chunks.",
   "Reduced draws far terrain coarser: faster on this integrated GPU.": "Reduced draws far terrain coarser: faster on this integrated GPU.",
@@ -173,7 +170,6 @@
   "How far mobs, crops and machines keep working. CPU time.": "How far mobs, crops and machines keep working. CPU time.",
   "How far away mobs and items are drawn, as a share of normal.": "How far away mobs and items are drawn, as a share of normal.",
   "Skips terrain hidden behind closed sections. Off costs a lot.": "Skips terrain hidden behind closed sections. Off costs a lot.",
-  "Hides models behind opaque blocks. Entities update. Off with custom packs.": "Hides models behind opaque blocks. Entities update. Off with custom packs.",
   "Meshed sections uploaded per frame. Lower is smoother while loading.": "Meshed sections uploaded per frame. Lower is smoother while loading.",
   "Soft shadows in corners. Costs chunk building time only.": "Soft shadows in corners. Costs chunk building time only.",
   "Smaller copies of block textures for distant terrain: less shimmer.": "Smaller copies of block textures for distant terrain: less shimmer.",
@@ -309,5 +305,36 @@
   "horizon.osk.close": "Close",
   "horizon.extras.chat_animation.tooltip": "A new chat line slides in from the left while it fades in, instead of appearing whole.",
   "horizon.extras.chat_indicator.tooltip": "The coloured bar at the left of a chat line.",
-  "horizon.extras.splitscreen.tooltip": "In a world, another controller can join as a new player: press A when it asks, then pick a profile and where to play."
+  "horizon.extras.splitscreen.tooltip": "In a world, another controller can join as a new player: press A when it asks, then pick a profile and where to play.",
+  "Culling": "Culling",
+  "Hides models behind opaque blocks. Async checks off-thread; entities tick.": "Hides models behind opaque blocks. Async checks off-thread; entities tick.",
+  "Leaf Culling": "Leaf Culling",
+  "Every leaf face. Vanilla's fancy leaves.": "Every leaf face. Vanilla's fancy leaves.",
+  "Distant Plant Dither": "Distant Plant Dither",
+  "Keeps fine plants in high-res packs from fading far away.": "Keeps fine plants in high-res packs from fading far away.",
+  "Screenshot Quality": "Screenshot Quality",
+  "F2 screenshots at this many times the game's resolution. Higher takes longer.": "F2 screenshots at this many times the game's resolution. Higher takes longer.",
+  "Frame Generation": "Frame Generation",
+  "Shows a made-up frame between each two real ones: smoother, a little more lag.": "Shows a made-up frame between each two real ones: smoother, a little more lag.",
+  "Shadow Cache": "Shadow Cache",
+  "Reuses the pack shadow map when sun, view and world match. Off by default.": "Reuses the pack shadow map when sun, view and world match. Off by default.",
+  "Synchronous": "Synchronous",
+  "Asynchronous": "Asynchronous",
+  "Solid": "Solid",
+  "Solid Aggressive": "Solid Aggressive",
+  "Hollow": "Hollow",
+  "Leaves fully inside a canopy draw solid: fewer see-through layers.": "Leaves fully inside a canopy draw solid: fewer see-through layers.",
+  "Leaves with one open side draw solid too: faster, chunkier edges.": "Leaves with one open side draw solid too: faster, chunkier edges.",
+  "Drops faces between leaves: faster, but gaps look through.": "Drops faces between leaves: faster, but gaps look through.",
+  "Hotbar: Previous Slot": "Hotbar: Previous Slot",
+  "Hotbar: Next Slot": "Hotbar: Next Slot",
+  "horizon.agent.connected.one": "Connected: 1 agent connection",
+  "horizon.agent.connected.many": "Connected: %s agent connections",
+  "horizon.agent.connected.one_ago": "Connected: 1 agent connection, last command %s s ago",
+  "horizon.agent.connected.many_ago": "Connected: %s agent connections, last command %s s ago",
+  "horizon.agent.waiting": "Waiting for an agent.",
+  "horizon.agent.off": "Off: agents can't reach this game.",
+  "horizon.agent.session_opened": "Opened for this session by the program that started the game.",
+  "horizon.agent.socket": "Socket: %s (copy the details for its full path)",
+  "horizon.agent.local_only": "Local only: agents on this computer, never the network."
 }

crates/horizon-client/assets/horizon/lang/es_es.json

@@ -140,10 +140,7 @@
   "%s per frame": "%s por fotograma",
   "%s MiB/frame": "%s MiB/fotograma",
   "%s KiB/frame": "%s KiB/fotograma",
-  "%s nits": "%s nits",
   "Auto (%s)": "Automático (%s)",
-  "Auto (%s nits)": "Automático (%s nits)",
-  "%.2f nits": "%.2f nits",
   "Full-detail terrain range. LOD Distance can extend local worlds farther.": "Alcance del terreno con todo el detalle. La distancia LOD puede extender más los mundos locales.",
   "Coarse distant terrain in local worlds. Integrated GPUs stop at 128 chunks.": "Terreno lejano de baja resolución en mundos locales. Las GPU integradas se limitan a 128 chunks.",
   "Reduced draws far terrain coarser: faster on this integrated GPU.": "Reducido dibuja el terreno lejano con menos detalle: más rápido en esta GPU integrada.",
@@ -161,7 +158,6 @@
   "How far mobs, crops and machines keep working. CPU time.": "Hasta dónde siguen funcionando mobs, cultivos y máquinas. Tiempo de CPU.",
   "How far away mobs and items are drawn, as a share of normal.": "A qué distancia se dibujan mobs y objetos, como proporción de lo normal.",
   "Skips terrain hidden behind closed sections. Off costs a lot.": "Omite el terreno oculto tras secciones cerradas. Desactivarlo cuesta mucho.",
-  "Hides models behind opaque blocks. Entities update. Off with custom packs.": "Oculta modelos tras bloques opacos. Las entidades se actualizan. Desactivado con paquetes personalizados.",
   "Meshed sections uploaded per frame. Lower is smoother while loading.": "Secciones malladas subidas por fotograma. Menos es más fluido durante la carga.",
   "Soft shadows in corners. Costs chunk building time only.": "Sombras suaves en las esquinas. Solo cuesta tiempo de construcción de chunks.",
   "Smaller copies of block textures for distant terrain: less shimmer.": "Copias más pequeñas de las texturas de bloques para el terreno lejano: menos parpadeo.",

crates/horizon-client/assets/horizon/lang/fr_fr.json

@@ -95,6 +95,7 @@
   "UI Brightness": "Luminosité UI",
   "Battery Mode": "Mode batterie",
   "Graphics API": "API graphique",
+  "Translucent Batching": "Regroupement translucide",
   "Performance Overlay": "Infos de perfs",
   "Full Detail Distance": "Dist. détail",
   "On": "Oui",
@@ -142,14 +143,12 @@
   "This feature is not yet available in Horizon.": "Cette fonction n'est pas encore disponible dans Horizon.",
   "Your display or system doesn't offer HDR output.": "Votre écran ou votre système ne propose pas de sortie HDR.",
   "Turn HDR on to use it.": "Activez le HDR pour l'utiliser.",
+  "Your GPU or graphics API doesn't support it.": "Votre GPU ou votre API graphique ne le prend pas en charge.",
   "%s chunks": "%s chunks",
   "%s per frame": "%s par image",
   "%s MiB/frame": "%s MiB/image",
   "%s KiB/frame": "%s KiB/image",
-  "%s nits": "%s nits",
   "Auto (%s)": "Auto (%s)",
-  "Auto (%s nits)": "Auto (%s nits)",
-  "%.2f nits": "%.2f nits",
   "Full-detail terrain range. LOD Distance can extend local worlds farther.": "Terrain en détail complet. La distance LOD va plus loin.",
   "Coarse distant terrain in local worlds. Integrated GPUs stop at 128 chunks.": "Terrain lointain simplifié, mondes locaux. GPU intégrés : 128 max.",
   "Reduced draws far terrain coarser: faster on this integrated GPU.": "Réduit : terrain lointain simplifié, plus rapide sur ce GPU.",
@@ -167,7 +166,6 @@
   "How far mobs, crops and machines keep working. CPU time.": "Portée d'activité des créatures, cultures, machines. Coût : CPU.",
   "How far away mobs and items are drawn, as a share of normal.": "Distance des créatures et objets, en part de la normale.",
   "Skips terrain hidden behind closed sections. Off costs a lot.": "Ignore le terrain caché. Désactiver coûte cher.",
-  "Hides models behind opaque blocks. Entities update. Off with custom packs.": "Masque les modèles derrière les blocs. Éteindre avec packs.",
   "Meshed sections uploaded per frame. Lower is smoother while loading.": "Sections maillées par image. Moins : chargement plus fluide.",
   "Soft shadows in corners. Costs chunk building time only.": "Ombres douces dans les coins. Coût : construction des chunks.",
   "Smaller copies of block textures for distant terrain: less shimmer.": "Textures réduites au loin : moins de scintillement.",
@@ -201,6 +199,7 @@
   "60 FPS cap (30 in menus or unfocused), half the workers: less power.": "60 FPS max (30 en menu/sans focus), moitié de threads : économie.",
   "Threads that generate, light and mesh chunks. Next start.": "Threads de génération, lumière et maillage. Au redémarrage.",
   "Vulkan, then DirectX 12 (Windows) or OpenGL (Linux) where it fails. Next start.": "Vulkan, sinon DirectX 12 (Windows) ou OpenGL (Linux). Au redémarrage.",
+  "Water and glass in one buffer: fewer draw calls, a bit more VRAM. Next start.": "Eau et verre dans un seul tampon : moins d'appels de dessin, un peu plus de VRAM. Au redémarrage.",
   "Mesh data sent to the GPU per frame. Lower is smoother while loading.": "Données de maillage vers le GPU par image. Moins : plus fluide.",
   "Frame rate and frame times over the game, with a graph.": "Fréquence et temps d'image par-dessus le jeu, avec un graphique.",
   "horizon.multiplayer.finding_friend": "Recherche du monde de votre ami...",
@@ -289,5 +288,53 @@
   "horizon.multiplayer.not_signed_in": "Ce serveur est en mode en ligne. Connectez-vous avec votre compte Microsoft dans le lanceur Horizon pour le rejoindre.",
   "horizon.multiplayer.invalid_address": "Adresse de serveur invalide : %s",
   "horizon.multiplayer.connected_friend_direct": "Connecté directement à votre ami...",
-  "horizon.multiplayer.connected_friend_relay": "Connecté à votre ami via le relais..."
+  "horizon.multiplayer.connected_friend_relay": "Connecté à votre ami via le relais...",
+  "Culling": "Occlusion",
+  "Hides models behind opaque blocks. Async checks off-thread; entities tick.": "Masque les modèles derrière les blocs opaques. Vérification en arrière-plan ; les entités continuent.",
+  "Leaf Culling": "Occlusion feuillage",
+  "Every leaf face. Vanilla's fancy leaves.": "Toutes les faces de feuillage, comme les feuilles détaillées de Minecraft.",
+  "Distant Plant Dither": "Tramage des plantes",
+  "Keeps fine plants in high-res packs from fading far away.": "Empêche les plantes fines des packs haute résolution de s'estomper au loin.",
+  "Screenshot Quality": "Qualité des captures",
+  "F2 screenshots at this many times the game's resolution. Higher takes longer.": "Captures F2 à ce multiple de la résolution du jeu. Plus c'est haut, plus c'est long.",
+  "Frame Generation": "Génération d'images",
+  "Shows a made-up frame between each two real ones: smoother, a little more lag.": "Insère une image calculée entre deux vraies : plus fluide, un peu plus de latence.",
+  "Shadow Cache": "Cache des ombres",
+  "Reuses the pack shadow map when sun, view and world match. Off by default.": "Réutilise la carte d'ombres du pack si soleil, vue et monde sont identiques. Désactivé par défaut.",
+  "Synchronous": "Synchrone",
+  "Asynchronous": "Asynchrone",
+  "Solid": "Opaque",
+  "Solid Aggressive": "Opaque agressif",
+  "Hollow": "Creux",
+  "Leaves fully inside a canopy draw solid: fewer see-through layers.": "Les feuilles au cœur d'un feuillage sont opaques : moins de couches transparentes.",
+  "Leaves with one open side draw solid too: faster, chunkier edges.": "Les feuilles avec un côté ouvert sont aussi opaques : plus rapide, bords plus grossiers.",
+  "Drops faces between leaves: faster, but gaps look through.": "Supprime les faces entre feuilles : plus rapide, mais on voit à travers les trous.",
+  "Hotbar: Previous Slot": "Barre d'action : case précédente",
+  "Hotbar: Next Slot": "Barre d'action : case suivante",
+  "horizon.agent.connected.one": "Connecté : 1 connexion d'agent",
+  "horizon.agent.connected.many": "Connecté : %s connexions d'agent",
+  "horizon.agent.connected.one_ago": "Connecté : 1 connexion d'agent, dernière commande il y a %s s",
+  "horizon.agent.connected.many_ago": "Connecté : %s connexions d'agent, dernière commande il y a %s s",
+  "horizon.agent.waiting": "En attente d'un agent.",
+  "horizon.agent.off": "Désactivé : les agents ne peuvent pas joindre ce jeu.",
+  "horizon.agent.session_opened": "Ouvert pour cette session par le programme qui a lancé le jeu.",
+  "horizon.agent.socket": "Socket : %s (copiez les détails pour le chemin complet)",
+  "horizon.agent.local_only": "Local uniquement : agents sur cet ordinateur, jamais via le réseau.",
+  "horizon.extras.chat_animation": "Chat fluide",
+  "horizon.extras.chat_animation.tooltip": "Une nouvelle ligne de chat glisse depuis la gauche en apparaissant progressivement, au lieu d'apparaître d'un coup.",
+  "horizon.extras.chat_indicator": "Marqueur de message",
+  "horizon.extras.chat_indicator.tooltip": "La barre colorée à gauche d'une ligne de chat.",
+  "horizon.extras.header.chat": "Chat",
+  "horizon.extras.header.particles": "Particules",
+  "horizon.extras.header.sound": "Son",
+  "horizon.extras.hide_block_particles": "Masquer particules",
+  "horizon.extras.hide_block_particles.tooltip": "Masque les débris qui jaillissent d'un bloc cassé et s'effritent de celui que vous minez. Les autres particules restent.",
+  "horizon.extras.splitscreen": "Écran partagé",
+  "horizon.extras.splitscreen.tooltip": "Dans un monde, une autre manette peut rejoindre en tant que nouveau joueur : appuyez sur A quand c'est demandé, puis choisissez un profil et où jouer.",
+  "horizon.extras.ui_sound_reserve": "Canaux pour sons UI",
+  "horizon.extras.ui_sound_reserve.tooltip": "Les sons du monde laissent 16 des 247 canaux sonores libres, pour qu'un déluge de sons (une grosse explosion) ne couvre pas les clics de menu.",
+  "horizon.pages.open.split_setup": "Écran partagé...",
+  "horizon.pages.split_settings": "Options de l'écran partagé",
+  "horizon.pages.split_setup": "Écran partagé",
+  "horizon.pages.split_setup.tooltip": "Joueurs sur cet ordinateur : des manettes peuvent rejoindre votre monde."
 }

crates/horizon-client/assets/horizon/lang/pl_pl.json

@@ -95,6 +95,7 @@
   "UI Brightness": "Jasność interfejsu",
   "Battery Mode": "Tryb baterii",
   "Graphics API": "API grafiki",
+  "Translucent Batching": "Grupowanie półprzezroczystych",
   "Performance Overlay": "Nakładka wydajności",
   "Full Detail Distance": "Zasięg detali",
   "On": "Wł.",
@@ -142,14 +143,12 @@
   "This feature is not yet available in Horizon.": "Ta funkcja nie jest jeszcze dostępna w Horizon.",
   "Your display or system doesn't offer HDR output.": "Twój wyświetlacz lub system nie obsługuje wyjścia HDR.",
   "Turn HDR on to use it.": "Włącz HDR, aby tego użyć.",
+  "Your GPU or graphics API doesn't support it.": "Twoje GPU lub API graficzne tego nie obsługuje.",
   "%s chunks": "%s chunków",
   "%s per frame": "%s na klatkę",
   "%s MiB/frame": "%s MiB/klatka",
   "%s KiB/frame": "%s KiB/klatka",
-  "%s nits": "%s nitów",
   "Auto (%s)": "Auto (%s)",
-  "Auto (%s nits)": "Auto (%s nitów)",
-  "%.2f nits": "%.2f nitów",
   "Full-detail terrain range. LOD Distance can extend local worlds farther.": "Zasięg terenu w pełnych szczegółach. Zasięg LOD sięga dalej.",
   "Coarse distant terrain in local worlds. Integrated GPUs stop at 128 chunks.": "Uproszczony odległy teren w światach lokalnych. Zintegr. GPU: do 128.",
   "Reduced draws far terrain coarser: faster on this integrated GPU.": "Ograniczone: odległy teren rysowany prościej, szybciej na tym GPU.",
@@ -167,7 +166,6 @@
   "How far mobs, crops and machines keep working. CPU time.": "Jak daleko stworzenia, uprawy i maszyny nadal działają. Czas procesora.",
   "How far away mobs and items are drawn, as a share of normal.": "Odległość rysowania stworzeń i przedmiotów, jako ułamek normy.",
   "Skips terrain hidden behind closed sections. Off costs a lot.": "Pomija teren ukryty za zamkniętymi sekcjami. Wyłączone dużo kosztuje.",
-  "Hides models behind opaque blocks. Entities update. Off with custom packs.": "Ukrywa modele za pełnymi blokami. Wył. przy własnych paczkach.",
   "Meshed sections uploaded per frame. Lower is smoother while loading.": "Liczba sekcji siatki wysyłanych na klatkę. Mniej to płynniej podczas ładowania.",
   "Soft shadows in corners. Costs chunk building time only.": "Miękkie cienie w narożnikach. Kosztuje tylko czas budowania chunków.",
   "Smaller copies of block textures for distant terrain: less shimmer.": "Mniejsze kopie tekstur bloków dla odległego terenu: mniej migotania.",
@@ -201,6 +199,7 @@
   "60 FPS cap (30 in menus or unfocused), half the workers: less power.": "Limit 60 FPS (30 w menu/bez fokusu), połowa wątków: mniej energii.",
   "Threads that generate, light and mesh chunks. Next start.": "Wątki generujące, oświetlające i meshujące chunki. Po restarcie.",
   "Vulkan, then DirectX 12 (Windows) or OpenGL (Linux) where it fails. Next start.": "Vulkan, awaryjnie DirectX 12 (Windows) / OpenGL (Linux). Po restarcie.",
+  "Water and glass in one buffer: fewer draw calls, a bit more VRAM. Next start.": "Woda i szkło w jednym buforze: mniej wywołań rysowania, trochę więcej VRAM. Po restarcie.",
   "Mesh data sent to the GPU per frame. Lower is smoother while loading.": "Dane siatki wysyłane do GPU na klatkę. Mniej to płynniej podczas ładowania.",
   "Frame rate and frame times over the game, with a graph.": "Liczba klatek i czasy klatek nad grą, z wykresem.",
   "horizon.multiplayer.finding_friend": "Szukanie świata znajomego…",
@@ -289,5 +288,53 @@
   "horizon.osk.delete": "Usuń",
   "horizon.osk.type": "Wpisz",
   "horizon.osk.symbols": "Symbole",
-  "horizon.osk.close": "Zamknij"
+  "horizon.osk.close": "Zamknij",
+  "Culling": "Pomijanie",
+  "Hides models behind opaque blocks. Async checks off-thread; entities tick.": "Ukrywa modele za pełnymi blokami. Sprawdzanie w tle; byty nadal się aktualizują.",
+  "Leaf Culling": "Pomijanie liści",
+  "Every leaf face. Vanilla's fancy leaves.": "Każda ściana liści, tak jak rysuje je Minecraft.",
+  "Distant Plant Dither": "Dithering roślin",
+  "Keeps fine plants in high-res packs from fading far away.": "Zapobiega zanikaniu drobnych roślin w paczkach wysokiej rozdzielczości w oddali.",
+  "Screenshot Quality": "Jakość zrzutów ekranu",
+  "F2 screenshots at this many times the game's resolution. Higher takes longer.": "Zrzuty F2 w tylokrotności rozdzielczości gry. Więcej trwa dłużej.",
+  "Frame Generation": "Generowanie klatek",
+  "Shows a made-up frame between each two real ones: smoother, a little more lag.": "Pokazuje wygenerowaną klatkę między każdymi dwiema prawdziwymi: płynniej, trochę większe opóźnienie.",
+  "Shadow Cache": "Pamięć cieni",
+  "Reuses the pack shadow map when sun, view and world match. Off by default.": "Używa ponownie mapy cieni paczki, gdy słońce, widok i świat się zgadzają. Domyślnie wyłączone.",
+  "Synchronous": "Synchroniczne",
+  "Asynchronous": "Asynchroniczne",
+  "Solid": "Pełne",
+  "Solid Aggressive": "Pełne, agresywnie",
+  "Hollow": "Puste",
+  "Leaves fully inside a canopy draw solid: fewer see-through layers.": "Liście w środku korony rysują się jako pełne: mniej przezroczystych warstw.",
+  "Leaves with one open side draw solid too: faster, chunkier edges.": "Liście z jedną otwartą stroną też rysują się jako pełne: szybciej, grubsze krawędzie.",
+  "Drops faces between leaves: faster, but gaps look through.": "Pomija ściany między liśćmi: szybciej, ale luki są przezroczyste.",
+  "Hotbar: Previous Slot": "Pasek szybkiego wyboru: poprzednie pole",
+  "Hotbar: Next Slot": "Pasek szybkiego wyboru: następne pole",
+  "horizon.agent.connected.one": "Połączono: 1 połączenie agenta",
+  "horizon.agent.connected.many": "Połączenia agenta: %s",
+  "horizon.agent.connected.one_ago": "Połączono: 1 połączenie agenta, ostatnie polecenie %s s temu",
+  "horizon.agent.connected.many_ago": "Połączenia agenta: %s, ostatnie polecenie %s s temu",
+  "horizon.agent.waiting": "Czeka na agenta.",
+  "horizon.agent.off": "Wyłączone: agenci nie mają dostępu do tej gry.",
+  "horizon.agent.session_opened": "Otwarte na tę sesję przez program, który uruchomił grę.",
+  "horizon.agent.socket": "Gniazdo: %s (skopiuj dane, aby poznać pełną ścieżkę)",
+  "horizon.agent.local_only": "Tylko lokalnie: agenci na tym komputerze, nigdy przez sieć.",
+  "horizon.extras.chat_animation": "Płynny czat",
+  "horizon.extras.chat_animation.tooltip": "Nowa linia czatu wsuwa się z lewej i pojawia stopniowo, zamiast wyświetlać się od razu w całości.",
+  "horizon.extras.chat_indicator": "Znacznik wiadomości",
+  "horizon.extras.chat_indicator.tooltip": "Kolorowy pasek po lewej stronie linii czatu.",
+  "horizon.extras.header.chat": "Czat",
+  "horizon.extras.header.particles": "Cząsteczki",
+  "horizon.extras.header.sound": "Dźwięk",
+  "horizon.extras.hide_block_particles": "Ukryj cząstki bloków",
+  "horizon.extras.hide_block_particles.tooltip": "Ukrywa cząsteczki odłamków, które tryskają ze zniszczonego bloku i kruszą się z tego, który kopiesz. Inne cząsteczki zostają.",
+  "horizon.extras.splitscreen": "Podzielony ekran",
+  "horizon.extras.splitscreen.tooltip": "W świecie może dołączyć kolejny kontroler jako nowy gracz: naciśnij A, gdy zapyta, potem wybierz profil i miejsce gry.",
+  "horizon.extras.ui_sound_reserve": "Kanały dla dźwięków UI",
+  "horizon.extras.ui_sound_reserve.tooltip": "Dźwięki świata zostawiają wolnych 16 z 247 kanałów, by ich nawał (duży wybuch) nie wyciszył kliknięć w menu.",
+  "horizon.pages.open.split_setup": "Podzielony ekran…",
+  "horizon.pages.split_settings": "Ustawienia podzielonego ekranu",
+  "horizon.pages.split_setup": "Podzielony ekran",
+  "horizon.pages.split_setup.tooltip": "Gracze na tym komputerze: kontrolery mogą dołączyć do twojego świata."
 }

crates/horizon-client/assets/horizon/lang/ru_ru.json

@@ -139,10 +139,7 @@
   "%s per frame": "%s за кадр",
   "%s MiB/frame": "%s МиБ/кадр",
   "%s KiB/frame": "%s КиБ/кадр",
-  "%s nits": "%s нит",
   "Auto (%s)": "Авто (%s)",
-  "Auto (%s nits)": "Авто (%s нит)",
-  "%.2f nits": "%.2f нит",
   "Full-detail terrain range. LOD Distance can extend local worlds farther.": "Дальность прорисованного рельефа в деталях. Дистанция LOD может продлить её для локальных миров.",
   "Coarse distant terrain in local worlds. Integrated GPUs stop at 128 chunks.": "Грубый дальний рельеф в локальных мирах. На встроенной графике — не дальше 128 чанков.",
   "Reduced draws far terrain coarser: faster on this integrated GPU.": "«Снижено» рисует дальний рельеф грубее: на этой встроенной видеокарте быстрее.",
@@ -160,7 +157,6 @@
   "How far mobs, crops and machines keep working. CPU time.": "Как далеко мобы, посевы и механизмы продолжают работать. Нагрузка на процессор.",
   "How far away mobs and items are drawn, as a share of normal.": "С какой дистанции рисуются мобы и предметы, в долях от обычной.",
   "Skips terrain hidden behind closed sections. Off costs a lot.": "Пропускает рельеф, скрытый за закрытыми секциями. Выключено — дорого.",
-  "Hides models behind opaque blocks. Entities update. Off with custom packs.": "Прячет модели за непрозрачными блоками. Сущности тикают. Выключать со своими наборами.",
   "Meshed sections uploaded per frame. Lower is smoother while loading.": "Секций меша за кадр. Меньше — плавнее во время загрузки.",
   "Soft shadows in corners. Costs chunk building time only.": "Мягкие тени по углам. Замедляет только построение чанков.",
   "Smaller copies of block textures for distant terrain: less shimmer.": "Уменьшенные копии текстур блоков для дали: меньше мерцания.",

crates/horizon-client/assets/horizon/lang/tr_tr.json

@@ -140,10 +140,7 @@
   "%s per frame": "Kare başına %s",
   "%s MiB/frame": "Kare başına %s MiB",
   "%s KiB/frame": "Kare başına %s KiB",
-  "%s nits": "%s nit",
   "Auto (%s)": "Otomatik (%s)",
-  "Auto (%s nits)": "Otomatik (%s nit)",
-  "%.2f nits": "%.2f nit",
   "Full-detail terrain range. LOD Distance can extend local worlds farther.": "Arazinin tam ayrıntıyla görüntülendiği mesafe. LOD Mesafesi, yerel dünyalarda bu mesafeyi daha da artırabilir.",
   "Coarse distant terrain in local worlds. Integrated GPUs stop at 128 chunks.": "Yerel dünyalarda uzaktaki arazileri daha düşük ayrıntıyla görüntüler. Tümleşik GPU'larda sınır 128 parçadır.",
   "Reduced draws far terrain coarser: faster on this integrated GPU.": "Düşük ayarı, uzak arazileri daha düşük ayrıntıyla görüntüler. Bu tümleşik GPU'da daha yüksek performans sağlar.",
@@ -161,7 +158,6 @@
   "How far mobs, crops and machines keep working. CPU time.": "Yaratıkların, ekinlerin ve makinelerin ne kadar uzaktan çalışmaya devam edeceğini belirler. İşlemci gücü kullanır.",
   "How far away mobs and items are drawn, as a share of normal.": "Yaratıkların ve eşyaların ne kadar uzaktan görüntüleneceğini, normal mesafeye oranla belirler.",
   "Skips terrain hidden behind closed sections. Off costs a lot.": "Kapalı alanların arkasında kalan arazilerin çizilmesini önler. Kapalı olması ciddi performans kaybına neden olur.",
-  "Hides models behind opaque blocks. Entities update. Off with custom packs.": "Opak blokların arkasında kalan modelleri gizler. Varlıkların güncellemeleri devam eder. Özel paketler kullanırken kapatın.",
   "Meshed sections uploaded per frame. Lower is smoother while loading.": "Her karede GPU'ya yüklenen oluşturulmuş bölüm sayısı. Daha düşük değerler yükleme sırasında daha akıcı bir deneyim sağlar.",
   "Soft shadows in corners. Costs chunk building time only.": "Köşelerde yumuşak gölgeler oluşturur. Yalnızca parça oluşturma süresini etkiler.",
   "Smaller copies of block textures for distant terrain: less shimmer.": "Uzak arazilerde blok dokularının daha küçük kopyalarını kullanır. Titreşimli görüntüyü azaltır.",

crates/horizon-client/assets/horizon/lang/uk_ua.json

@@ -95,6 +95,7 @@
   "UI Brightness": "Яскравість UI",
   "Battery Mode": "Режим батареї",
   "Graphics API": "API графіки",
+  "Translucent Batching": "Групування напівпрозорого",
   "Performance Overlay": "Накладка швидкодії",
   "Full Detail Distance": "Дальність деталей",
   "On": "Увімк.",
@@ -142,14 +143,12 @@
   "This feature is not yet available in Horizon.": "Ця функція ще недоступна в Horizon.",
   "Your display or system doesn't offer HDR output.": "Ваш дисплей або система не підтримує вивід HDR.",
   "Turn HDR on to use it.": "Увімкніть HDR, щоб користуватися цим.",
+  "Your GPU or graphics API doesn't support it.": "Ваш GPU або графічний API цього не підтримує.",
   "%s chunks": "%s чанків",
   "%s per frame": "%s на кадр",
   "%s MiB/frame": "%s MiB/кадр",
   "%s KiB/frame": "%s KiB/кадр",
-  "%s nits": "%s ніт",
   "Auto (%s)": "Авто (%s)",
-  "Auto (%s nits)": "Авто (%s ніт)",
-  "%.2f nits": "%.2f ніт",
   "Full-detail terrain range. LOD Distance can extend local worlds farther.": "Дальність повних деталей. Дальність LOD сягає далі.",
   "Coarse distant terrain in local worlds. Integrated GPUs stop at 128 chunks.": "Спрощена далека місцевість локальних світів. Інтегр. GPU: до 128.",
   "Reduced draws far terrain coarser: faster on this integrated GPU.": "Знижена: далека місцевість простіша, швидше на цьому GPU.",
@@ -167,7 +166,6 @@
   "How far mobs, crops and machines keep working. CPU time.": "Як далеко працюють моби, посіви й механізми. Витрачає CPU.",
   "How far away mobs and items are drawn, as a share of normal.": "Відстань малювання мобів і предметів, у частці від норми.",
   "Skips terrain hidden behind closed sections. Off costs a lot.": "Пропускає приховану місцевість. Вимкнення коштує дорого.",
-  "Hides models behind opaque blocks. Entities update. Off with custom packs.": "Ховає моделі за блоками. Вимкніть із власними пакетами.",
   "Meshed sections uploaded per frame. Lower is smoother while loading.": "Секцій сітки за кадр. Менше — плавніше під час завантаження.",
   "Soft shadows in corners. Costs chunk building time only.": "М’які тіні в кутах. Витрачає лише час на побудову чанків.",
   "Smaller copies of block textures for distant terrain: less shimmer.": "Менші копії текстур блоків для віддаленої місцевості: менше мерехтіння.",
@@ -201,6 +199,7 @@
   "60 FPS cap (30 in menus or unfocused), half the workers: less power.": "60 FPS (30 у меню/без фокуса), половина потоків: економія.",
   "Threads that generate, light and mesh chunks. Next start.": "Потоки генерації, світла й сітки чанків. Після перезапуску.",
   "Vulkan, then DirectX 12 (Windows) or OpenGL (Linux) where it fails. Next start.": "Vulkan, інакше DirectX 12 (Windows)/OpenGL (Linux). Після рестарту.",
+  "Water and glass in one buffer: fewer draw calls, a bit more VRAM. Next start.": "Вода і скло в одному буфері: менше викликів малювання, трохи більше VRAM. Після перезапуску.",
   "Mesh data sent to the GPU per frame. Lower is smoother while loading.": "Дані сітки до GPU за кадр. Менше — плавніше завантаження.",
   "Frame rate and frame times over the game, with a graph.": "Частота та час кадрів поверх гри, з графіком.",
   "horizon.multiplayer.finding_friend": "Шукаємо світ друга…",
@@ -289,5 +288,53 @@
   "horizon.osk.delete": "Видалити",
   "horizon.osk.type": "Ввести",
   "horizon.osk.symbols": "Символи",
-  "horizon.osk.close": "Закрити"
+  "horizon.osk.close": "Закрити",
+  "Culling": "Відсікання",
+  "Hides models behind opaque blocks. Async checks off-thread; entities tick.": "Ховає моделі за непрозорими блоками. Перевірка у фоні; сутності оновлюються.",
+  "Leaf Culling": "Відсікання листя",
+  "Every leaf face. Vanilla's fancy leaves.": "Кожна грань листя, як це робить Minecraft у гарній графіці.",
+  "Distant Plant Dither": "Дизеринг рослин",
+  "Keeps fine plants in high-res packs from fading far away.": "Не дає дрібним рослинам у пакетах високої роздільності зникати здалеку.",
+  "Screenshot Quality": "Якість знімків екрана",
+  "F2 screenshots at this many times the game's resolution. Higher takes longer.": "Знімки F2 у стільки разів більшій роздільності, ніж гра. Більше значить довше.",
+  "Frame Generation": "Генерація кадрів",
+  "Shows a made-up frame between each two real ones: smoother, a little more lag.": "Показує згенерований кадр між кожними двома справжніми: плавніше, трохи більша затримка.",
+  "Shadow Cache": "Кеш тіней",
+  "Reuses the pack shadow map when sun, view and world match. Off by default.": "Повторно використовує карту тіней пакета, коли сонце, вигляд і світ збігаються. Типово вимкнено.",
+  "Synchronous": "Синхронно",
+  "Asynchronous": "Асинхронно",
+  "Solid": "Суцільне",
+  "Solid Aggressive": "Суцільне, агресивно",
+  "Hollow": "Порожнє",
+  "Leaves fully inside a canopy draw solid: fewer see-through layers.": "Листя всередині крони малюється суцільним: менше прозорих шарів.",
+  "Leaves with one open side draw solid too: faster, chunkier edges.": "Листя з одним відкритим боком теж малюється суцільним: швидше, грубіші краї.",
+  "Drops faces between leaves: faster, but gaps look through.": "Прибирає грані між листям: швидше, але прогалини прозорі.",
+  "Hotbar: Previous Slot": "Панель швидкого доступу: попередній слот",
+  "Hotbar: Next Slot": "Панель швидкого доступу: наступний слот",
+  "horizon.agent.connected.one": "Підключено: 1 з’єднання агента",
+  "horizon.agent.connected.many": "Підключено з’єднань агента: %s",
+  "horizon.agent.connected.one_ago": "Підключено: 1 з’єднання агента, остання команда %s с тому",
+  "horizon.agent.connected.many_ago": "Підключено з’єднань агента: %s, остання команда %s с тому",
+  "horizon.agent.waiting": "Очікування агента.",
+  "horizon.agent.off": "Вимкнено: агенти не можуть дістатися цієї гри.",
+  "horizon.agent.session_opened": "Відкрито на цей сеанс програмою, що запустила гру.",
+  "horizon.agent.socket": "Сокет: %s (скопіюйте дані, щоб побачити повний шлях)",
+  "horizon.agent.local_only": "Лише локально: агенти на цьому комп’ютері, ніколи через мережу.",
+  "horizon.extras.chat_animation": "Плавний чат",
+  "horizon.extras.chat_animation.tooltip": "Новий рядок чату виїжджає зліва, поступово з’являючись, замість того щоб з’явитися одразу.",
+  "horizon.extras.chat_indicator": "Позначка повідомлення",
+  "horizon.extras.chat_indicator.tooltip": "Кольорова смужка ліворуч від рядка чату.",
+  "horizon.extras.header.chat": "Чат",
+  "horizon.extras.header.particles": "Частинки",
+  "horizon.extras.header.sound": "Звук",
+  "horizon.extras.hide_block_particles": "Без частинок блоків",
+  "horizon.extras.hide_block_particles.tooltip": "Ховає частинки уламків, що розлітаються зі зламаного блока та осипаються з того, який ви ламаєте. Інші частинки залишаються.",
+  "horizon.extras.splitscreen": "Розділений екран",
+  "horizon.extras.splitscreen.tooltip": "У світі може долучитися ще один геймпад як новий гравець: натисніть A, коли запитає, потім виберіть профіль і де грати.",
+  "horizon.extras.ui_sound_reserve": "Канали для звуків UI",
+  "horizon.extras.ui_sound_reserve.tooltip": "Звуки у світі залишають вільними 16 із 247 звукових каналів, щоб їхній потік (великий вибух) не заглушив кліки в меню.",
+  "horizon.pages.open.split_setup": "Розділений екран…",
+  "horizon.pages.split_settings": "Налаштування розділеного екрана",
+  "horizon.pages.split_setup": "Розділений екран",
+  "horizon.pages.split_setup.tooltip": "Гравці на цьому комп’ютері: геймпади можуть долучитися до вашого світу."
 }

crates/horizon-client/assets/horizon/lang/zh_cn.json

@@ -89,6 +89,7 @@
   "UI Brightness": "界面亮度",
   "Battery Mode": "电池模式",
   "Graphics API": "图形 API",
+  "Translucent Batching": "半透明批处理",
   "Performance Overlay": "性能叠加层",
   "Full Detail Distance": "全细节距离",
   "On": "开",
@@ -136,14 +137,12 @@
   "This feature is not yet available in Horizon.": "此功能在 Horizon 中尚不可用。",
   "Your display or system doesn't offer HDR output.": "你的显示器或系统不支持 HDR 输出。",
   "Turn HDR on to use it.": "开启 HDR 后才能使用。",
+  "Your GPU or graphics API doesn't support it.": "你的 GPU 或图形 API 不支持此功能。",
   "%s chunks": "%s 个区块",
   "%s per frame": "每帧 %s",
   "%s MiB/frame": "每帧 %s MiB",
   "%s KiB/frame": "每帧 %s KiB",
-  "%s nits": "%s 尼特",
   "Auto (%s)": "自动（%s）",
-  "Auto (%s nits)": "自动（%s 尼特）",
-  "%.2f nits": "%.2f 尼特",
   "Full-detail terrain range. LOD Distance can extend local worlds farther.": "完整细节的地形范围。LOD 距离可以让本地世界延伸得更远。",
   "Coarse distant terrain in local worlds. Integrated GPUs stop at 128 chunks.": "本地世界的远景粗略地形。集成显卡最多 128 个区块。",
   "Reduced draws far terrain coarser: faster on this integrated GPU.": "“精简”把远景画得更粗略：在这块集成显卡上更快。",
@@ -161,7 +160,6 @@
   "How far mobs, crops and machines keep working. CPU time.": "生物、农作物和机器持续工作的距离。占用 CPU 时间。",
   "How far away mobs and items are drawn, as a share of normal.": "生物和物品的绘制距离，按正常值的比例。",
   "Skips terrain hidden behind closed sections. Off costs a lot.": "跳过被封闭区块遮挡的地形。关闭的开销很大。",
-  "Hides models behind opaque blocks. Entities update. Off with custom packs.": "隐藏不透明方块后面的模型。实体仍会更新。自定义资源包时应关闭。",
   "Meshed sections uploaded per frame. Lower is smoother while loading.": "每帧上传的网格化区块数。越低加载时越流畅。",
   "Soft shadows in corners. Costs chunk building time only.": "角落里的柔和阴影。只占用区块构建时间。",
   "Smaller copies of block textures for distant terrain: less shimmer.": "为远处地形生成更小的方块纹理副本：减少闪烁。",
@@ -195,6 +193,7 @@
   "60 FPS cap (30 in menus or unfocused), half the workers: less power.": "限制 60 FPS（菜单或失焦时 30），工作线程减半：更省电。",
   "Threads that generate, light and mesh chunks. Next start.": "负责生成、光照与网格化区块的线程数。下次启动生效。",
   "Vulkan, then DirectX 12 (Windows) or OpenGL (Linux) where it fails. Next start.": "优先 Vulkan，失败时用 DirectX 12（Windows）或 OpenGL（Linux）。下次启动生效。",
+  "Water and glass in one buffer: fewer draw calls, a bit more VRAM. Next start.": "水和玻璃放在同一个缓冲区：绘制调用更少，显存略多。下次启动生效。",
   "Mesh data sent to the GPU per frame. Lower is smoother while loading.": "每帧发送给 GPU 的网格数据。越低加载时越流畅。",
   "Frame rate and frame times over the game, with a graph.": "游戏运行时的帧率与帧时间，附带图表。",
   "horizon.multiplayer.finding_friend": "正在查找好友的世界…",
@@ -306,5 +305,36 @@
   "horizon.osk.close": "关闭",
   "horizon.extras.chat_animation.tooltip": "新聊天行从左侧滑入并淡入，而不是整行直接出现。",
   "horizon.extras.chat_indicator.tooltip": "聊天行左侧的彩色竖条。",
-  "horizon.extras.splitscreen.tooltip": "在世界中，另一个手柄可以以新玩家身份加入：提示时按 A，然后选择档案和游玩位置。"
+  "horizon.extras.splitscreen.tooltip": "在世界中，另一个手柄可以以新玩家身份加入：提示时按 A，然后选择档案和游玩位置。",
+  "Culling": "剔除",
+  "Hides models behind opaque blocks. Async checks off-thread; entities tick.": "隐藏不透明方块后面的模型。检测在后台线程进行，实体仍会更新。",
+  "Leaf Culling": "树叶剔除",
+  "Every leaf face. Vanilla's fancy leaves.": "绘制每个树叶面，与原版的华丽树叶一致。",
+  "Distant Plant Dither": "远处植物抖动",
+  "Keeps fine plants in high-res packs from fading far away.": "避免高分辨率资源包中的细小植物在远处逐渐消失。",
+  "Screenshot Quality": "截图质量",
+  "F2 screenshots at this many times the game's resolution. Higher takes longer.": "F2 截图的分辨率为游戏分辨率的这个倍数。越高耗时越长。",
+  "Frame Generation": "帧生成",
+  "Shows a made-up frame between each two real ones: smoother, a little more lag.": "在每两个真实帧之间插入一个生成帧：更流畅，延迟略增。",
+  "Shadow Cache": "阴影缓存",
+  "Reuses the pack shadow map when sun, view and world match. Off by default.": "太阳、视角和世界不变时重复使用资源包的阴影贴图。默认关闭。",
+  "Synchronous": "同步",
+  "Asynchronous": "异步",
+  "Solid": "实心",
+  "Solid Aggressive": "激进实心",
+  "Hollow": "镂空",
+  "Leaves fully inside a canopy draw solid: fewer see-through layers.": "树冠内部的树叶绘制为实心：透明层更少。",
+  "Leaves with one open side draw solid too: faster, chunkier edges.": "只有一面外露的树叶也绘制为实心：更快，边缘更粗糙。",
+  "Drops faces between leaves: faster, but gaps look through.": "省略树叶之间的面：更快，但缝隙会透视。",
+  "Hotbar: Previous Slot": "快捷栏：上一个栏位",
+  "Hotbar: Next Slot": "快捷栏：下一个栏位",
+  "horizon.agent.connected.one": "已连接：1 个代理连接",
+  "horizon.agent.connected.many": "已连接：%s 个代理连接",
+  "horizon.agent.connected.one_ago": "已连接：1 个代理连接，上次命令在 %s 秒前",
+  "horizon.agent.connected.many_ago": "已连接：%s 个代理连接，上次命令在 %s 秒前",
+  "horizon.agent.waiting": "正在等待代理。",
+  "horizon.agent.off": "关闭：代理无法访问此游戏。",
+  "horizon.agent.session_opened": "由启动游戏的程序为本次会话开启。",
+  "horizon.agent.socket": "套接字：%s（复制详细信息以获取完整路径）",
+  "horizon.agent.local_only": "仅限本机：此电脑上的代理可用，网络不可用。"
 }

crates/horizon-client/examples/chunk_load_bench.rs

@@ -5,13 +5,16 @@
 //!
 //!     cargo run --release -p horizon-client --example chunk_load_bench -- \
 //!         .local/horizon-client/26.3 [--seed 1234] [--center CX CZ] [--radius 8]
-//!         [--threads N] [--rounds 3]
+//!         [--threads N] [--rounds 3] [--mesh-threads N] [--json out.json]
 //!
 //! The default centre is the village of `tools/perf_bench.py`. The generation
 //! figure is wall time with N workers (the game's own pool); the mesh figure is
-//! this thread's CPU time in `Mesher::mesh`, the best of `--rounds`, so other
-//! work on the machine changes it less. The checksum of the meshes shows that an
-//! A/B pair of builds made the same ones.
+//! this thread's CPU time in the workers' path (`Mesher::mesh_reusing` with a
+//! recycled mesh and scratch, then `sort_solid`), each section's best of
+//! `--rounds`, so other work on the machine changes it less; then the wall time
+//! of `--mesh-threads` threads meshing them all at once. The checksum of the
+//! meshes (vertices and visibility) shows that an A/B pair of builds made the
+//! same ones.
 extern crate horizon_client_lib as horizon_client;
 use horizon_client::{
     assets::Assets,
@@ -20,7 +23,7 @@ use horizon_client::{
     chunk::HEIGHT,
     graphics::LeafCullingMode,
     light::LightTables,
-    mesher::{MeshTables, Mesher, Region, borrow},
+    mesher::{MeshScratch, MeshTables, Mesher, Region, SectionMesh, TerrainVertex, borrow},
     models,
     spans::thread_cpu,
     streaming::{Streaming, WorkerContext},
@@ -32,7 +35,10 @@ use horizon_world::registry::BlockStateId;
 use std::{
     hash::{DefaultHasher, Hash, Hasher},
     path::PathBuf,
-    sync::Arc,
+    sync::{
+        Arc,
+        atomic::{AtomicUsize, Ordering},
+    },
     thread,
     time::{Duration, Instant},
 };
@@ -131,43 +137,176 @@ fn main() -> Result<(), Error> {
         })
         .flat_map(|region| (0..HEIGHT / 16).map(move |sy| (region.clone(), sy)))
         .collect();
-    let mut best = Duration::MAX;
-    let (mut vertices, mut checksum) = (0, 0);
-    for _ in 0..rounds.max(1) {
-        let mut mesher = Mesher {
-            nether_shading: false,
-            shader_pack_lighting: false,
-            zoom: BiomeZoom::new(obfuscate_seed(seed)),
-            blend_radius: 2,
-            smooth_lighting: true,
-            cutout_leaves: true,
-            translucent_layers: &[],
-            leaf_culling: LeafCullingMode::Off,
-            assets: &context.assets,
-            render: &context.render,
-            tables: &context.tables,
-            biomes: &context.biomes,
-            visibility: context.tables.visibility.clone(),
-        };
-        vertices = 0;
-        let mut hash = DefaultHasher::new();
-        let mut spent = Duration::ZERO;
-        for (region, sy) in &regions {
-            let started = thread_cpu().ok_or("no thread CPU clock here")?;
-            let mesh = mesher.mesh(&borrow(region), *sy);
-            spent += thread_cpu().ok_or("no thread CPU clock here")? - started;
-            vertices += mesh.solid.len() + mesh.translucent.len();
-            bytemuck::cast_slice::<_, u8>(&mesh.solid).hash(&mut hash);
-            bytemuck::cast_slice::<_, u8>(&mesh.translucent).hash(&mut hash);
-        }
-        checksum = hash.finish();
-        best = best.min(spent);
-    }
+    let one = mesh_rounds(&context, seed, &regions, rounds)?;
+    let mut sorted = one.per_section.clone();
+    sorted.sort_unstable();
+    let pct = |p: f64| {
+        let i = ((sorted.len() as f64 - 1.0) * p).round() as usize;
+        sorted.get(i).map_or(0.0, |d| d.as_secs_f64() * 1e6)
+    };
+    let total: Duration = one.per_section.iter().sum();
+    let filled: Vec<Duration> = one
+        .per_section
+        .iter()
+        .zip(&one.vertices_per_section)
+        .filter(|&(_, &v)| v > 0)
+        .map(|(d, _)| *d)
+        .collect();
+    let filled_total: Duration = filled.iter().sum();
+    let bytes = one.vertices * std::mem::size_of::<TerrainVertex>();
     println!(
-        "meshed {} sections ({vertices} vertices, checksum {checksum:016x}) in {:.1} ms of CPU ({:.1} us per section)",
+        "meshed {} sections ({} with geometry, {} vertices, {:.1} MB of vertices, checksum {:016x}) in {:.1} ms of CPU ({:.1} us per section)",
         regions.len(),
-        best.as_secs_f64() * 1e3,
-        best.as_secs_f64() * 1e6 / regions.len().max(1) as f64
+        filled.len(),
+        one.vertices,
+        bytes as f64 / 1e6,
+        one.checksum,
+        total.as_secs_f64() * 1e3,
+        total.as_secs_f64() * 1e6 / regions.len().max(1) as f64
     );
+    println!(
+        "per section (best of {rounds} rounds, us): p50 {:.1} p90 {:.1} p99 {:.1} max {:.1}; with geometry: mean {:.1}; {:.0} sections/s per core",
+        pct(0.5),
+        pct(0.9),
+        pct(0.99),
+        pct(1.0),
+        filled_total.as_secs_f64() * 1e6 / filled.len().max(1) as f64,
+        regions.len() as f64 / total.as_secs_f64().max(1e-9),
+    );
+    // Every worker meshing at once: the throughput a world being explored gets,
+    // memory bandwidth and the allocator included.
+    let mesh_threads: usize = flag(&args, "--mesh-threads", threads);
+    let parallel = mesh_parallel(&context, seed, &regions, mesh_threads)?;
+    println!(
+        "{mesh_threads} threads meshed {} sections in {:.1} ms of wall time: {:.0} sections/s",
+        regions.len(),
+        parallel.as_secs_f64() * 1e3,
+        regions.len() as f64 / parallel.as_secs_f64().max(1e-9)
+    );
+    if let Some(path) = args
+        .iter()
+        .position(|a| a == "--json")
+        .and_then(|i| args.get(i + 1))
+    {
+        let json = format!(
+            concat!(
+                "{{\"sections\":{},\"filled\":{},\"vertices\":{},\"vertex_bytes\":{},",
+                "\"checksum\":\"{:016x}\",\"cpu_ms\":{:.3},\"p50_us\":{:.2},\"p90_us\":{:.2},",
+                "\"p99_us\":{:.2},\"max_us\":{:.2},\"filled_mean_us\":{:.2},",
+                "\"mesh_threads\":{},\"parallel_per_s\":{:.1}}}\n"
+            ),
+            regions.len(),
+            filled.len(),
+            one.vertices,
+            bytes,
+            one.checksum,
+            total.as_secs_f64() * 1e3,
+            pct(0.5),
+            pct(0.9),
+            pct(0.99),
+            pct(1.0),
+            filled_total.as_secs_f64() * 1e6 / filled.len().max(1) as f64,
+            mesh_threads,
+            regions.len() as f64 / parallel.as_secs_f64().max(1e-9),
+        );
+        std::fs::write(path, json)?;
+    }
     Ok(())
 }
+
+fn mesher<'a>(context: &'a WorkerContext, seed: i64) -> Mesher<'a> {
+    Mesher {
+        nether_shading: false,
+        shader_pack_lighting: false,
+        zoom: BiomeZoom::new(obfuscate_seed(seed)),
+        blend_radius: 2,
+        smooth_lighting: true,
+        cutout_leaves: true,
+        translucent_layers: &[],
+        leaf_culling: LeafCullingMode::Off,
+        assets: &context.assets,
+        render: &context.render,
+        tables: &context.tables,
+        biomes: &context.biomes,
+        visibility: context.tables.visibility.clone(),
+    }
+}
+
+struct Rounds {
+    /// Each section's CPU time, the least of the rounds.
+    per_section: Vec<Duration>,
+    vertices_per_section: Vec<usize>,
+    vertices: usize,
+    checksum: u64,
+}
+
+/// Meshes every section `rounds` times on this thread the way a worker does:
+/// one mesher (its face cache kept), one scratch, the mesh buffers recycled,
+/// and the solid quads sorted by side.
+fn mesh_rounds(
+    context: &WorkerContext,
+    seed: i64,
+    regions: &[(Region, i32)],
+    rounds: usize,
+) -> Result<Rounds, Error> {
+    let mut mesher = mesher(context, seed);
+    let mut scratch = MeshScratch::default();
+    let mut recycled = SectionMesh::default();
+    let mut per_section = vec![Duration::MAX; regions.len()];
+    let mut vertices_per_section = vec![0; regions.len()];
+    let mut checksum = 0;
+    for _ in 0..rounds.max(1) {
+        let mut hash = DefaultHasher::new();
+        for (i, (region, sy)) in regions.iter().enumerate() {
+            let started = thread_cpu().ok_or("no thread CPU clock here")?;
+            let mut mesh = mesher.mesh_reusing(&borrow(region), *sy, recycled, &mut scratch);
+            mesh.sort_solid();
+            let spent = thread_cpu().ok_or("no thread CPU clock here")? - started;
+            per_section[i] = per_section[i].min(spent);
+            vertices_per_section[i] = mesh.solid.len() + mesh.translucent.len();
+            bytemuck::cast_slice::<_, u8>(&mesh.solid).hash(&mut hash);
+            bytemuck::cast_slice::<_, u8>(&mesh.translucent).hash(&mut hash);
+            mesh.visibility.hash(&mut hash);
+            recycled = mesh;
+        }
+        checksum = hash.finish();
+    }
+    let vertices = vertices_per_section.iter().sum();
+    Ok(Rounds {
+        per_section,
+        vertices_per_section,
+        vertices,
+        checksum,
+    })
+}
+
+/// Wall time for `threads` workers to mesh every section once between them.
+fn mesh_parallel(
+    context: &WorkerContext,
+    seed: i64,
+    regions: &[(Region, i32)],
+    threads: usize,
+) -> Result<Duration, Error> {
+    let next = AtomicUsize::new(0);
+    let started = Instant::now();
+    thread::scope(|scope| {
+        for _ in 0..threads.max(1) {
+            scope.spawn(|| {
+                let mut mesher = mesher(context, seed);
+                let mut scratch = MeshScratch::default();
+                let mut recycled = SectionMesh::default();
+                loop {
+                    let i = next.fetch_add(1, Ordering::Relaxed);
+                    let Some((region, sy)) = regions.get(i) else {
+                        break;
+                    };
+                    let mut mesh =
+                        mesher.mesh_reusing(&borrow(region), *sy, recycled, &mut scratch);
+                    mesh.sort_solid();
+                    recycled = mesh;
+                }
+            });
+        }
+    });
+    Ok(started.elapsed())
+}

crates/horizon-client/examples/probe/scene_motion_probe.rs

@@ -536,6 +536,9 @@ pub fn main() -> Result<()> {
                     let flying = op["value"].as_bool().unwrap();
                     world.player.may_fly = op["may_fly"].as_bool().unwrap_or(flying);
                     world.player.flying = flying;
+                    if let Some(speed) = op.get("speed") {
+                        world.player.flying_speed = single(speed);
+                    }
                 }
                 "trigger" => world.player.jump_trigger_time = op["value"].as_i64().unwrap() as i32,
                 "delay" => world.player.no_jump_delay = op["value"].as_i64().unwrap() as i32,

crates/horizon-client/src/arrows.rs

@@ -403,6 +403,18 @@ pub fn clip_block_stop(
     collision: &BlockCollisionRegistry<'_>,
     from: Vec3,
     movement: Vec3,
+) -> Option<(Vec3, BlockPos, [i32; 3])> {
+    let (location, block, normal) = clip_block_hit(world, facts, collision, from, movement)?;
+    Some((back_off(location, movement), block, normal))
+}
+/// The clip of `clip_block_stop` before the back-off: the hit location (what a
+/// `BlockHitResult` carries), the block and the normal of the face.
+pub fn clip_block_hit(
+    world: &World,
+    facts: &BlockFacts,
+    collision: &BlockCollisionRegistry<'_>,
+    from: Vec3,
+    movement: Vec3,
 ) -> Option<(Vec3, BlockPos, [i32; 3])> {
     let to = Vec3::new(
         from.x + movement.x,
@@ -426,11 +438,7 @@ pub fn clip_block_stop(
     })
     .ok()
     .flatten()?;
-    Some((
-        back_off(hit.location, movement),
-        hit.block,
-        hit.direction.normal(),
-    ))
+    Some((hit.location, hit.block, hit.direction.normal()))
 }
 /// `AbstractArrow.onHitBlock`'s back-off: vanilla scales `(double) 0.05f` by
 /// `Math.signum` per axis, whose value at zero is zero (not Rust's -1.0).

crates/horizon-client/src/bin/horizon-ctl/commands.rs

@@ -214,6 +214,9 @@ pub const COMMANDS: &[Cmd] = &[
         mcp: true, local: true),
     cmd!("status", Session, "status", "game, renderer and streaming state (the scripting socket's original summary)",
         "Also what F3 shows: the overlay flags, the renderer, chunk streaming and memory.", ["horizon-ctl status"], &[], mcp: true, local: false),
+    cmd!("hello", Session, "hello", "the control protocol's version, the game's release and the command groups it serves",
+        "Replies protocol (MAJOR.MINOR.PATCH of the control protocol, docs/api/stability.md), release (the game's version, the string MCP serverInfo carries too) and features (the command groups the game answers, so a script can test for one before calling it).",
+        ["horizon-ctl hello"], &[], mcp: true, local: false),
     cmd!("worlds", Session, "worlds", "the saved worlds, newest first: folder, name, mode, last played, version",
         "folder is what open, world-rename, world-backup and world-delete take.", ["horizon-ctl worlds"], &[], mcp: true, local: false),
     cmd!("world-rename", Session, "world-rename FOLDER NAME", "rename a world, as Edit World does (its folder stays)",
@@ -444,7 +447,7 @@ pub const COMMANDS: &[Cmd] = &[
         "Add it to an MCP client as a stdio server: command horizon-ctl, args [\"mcp\"] (with --socket PATH first if needed). The screenshot tool returns the image.",
         ["horizon-ctl mcp"], &[], mcp: false, local: true),
     cmd!("bench", Scripting, "bench SECONDS", "reset frame stats, wait, reply with the summary", "", ["horizon-ctl bench 10"], &[p("seconds", Ty::Num, "how long to measure")], mcp: true, local: false),
-    cmd!("stats", Scripting, "stats [reset]", "frame-time summary since the last reset", "", ["horizon-ctl stats"], &[opt("reset", Ty::Bool, "start counting again")], mcp: true, local: false),
+    cmd!("stats", Scripting, "stats [reset] [raw]", "frame-time summary since the last reset", "", ["horizon-ctl stats"], &[opt("reset", Ty::Bool, "start counting again"), opt("raw", Ty::Bool, "every frame time too (frame_ms, cpu_ms, gpu_ms)")], mcp: true, local: false),
     cmd!("gpu-passes", Scripting, "gpu-passes [on|off]", "time Horizon's own render passes on the GPU, shown in F3 and in stats and bench", "", ["horizon-ctl gpu-passes on"], &[opt("mode", Ty::Enum(&["on", "off"]), "on or off; without it, only reports")], mcp: false, local: false),
     cmd!("fly", Scripting, "fly X1 Y1 Z1 X2 Y2 Z2 SECONDS [PITCH [raw]]", "fly the camera along a line, then reply with the frame summary",
         "The reply's tick_ms and tick_ms_max are the world's smoothed tick time over the flight (the server thread's when single player runs on one). With raw, the reply also lists every frame time in milliseconds (frame_ms).",

crates/horizon-client/src/client_lib.rs

@@ -10,17 +10,17 @@ pub mod block_contact;
 pub use horizon_client_render::{
     assets, atlas_sources, audio, auth, ban_notice, bidi, biome, block_edit, block_entities,
     block_entity_anim, block_entity_render, border_render, breaking, brewing, camera, chat, chunk,
-    chunk_map, cit, cit_assets, clouds, collisions, command_block, containers, crash, datapack,
-    dynamic_light, effects, environment, extras, fast_hash, fog, font, gfx, graphics,
-    graphics_style, graphics_ui, hdr_calibration, hud, hud_layout, hud_overlays, inventory_effects,
-    java_text, jigsaw_block, level_loading, light, lod, logging, menu_blur, mesher, minimap,
-    mipmap, mod_list, model_library, models, multiline_edit, native_emissive, options_file,
-    options_fixes, options_ui, overlay, pack_screen, packs, par, particles, poi_sections,
-    post_chain, potent_sulfur, preedit, providers, screen_draw, screen_effects, sculk,
-    section_mask, settings, shader_options, shader_pack_list, signs, skins, sound_engine,
-    sound_events, sound_preview, spans, split_layout, split_profiles, sprites, streaming,
-    structure_block, tab_list, telemetry, test_block, test_instance_block, testgen, title_edition,
-    trims, ui, vault, weather, widgets, world, worldborder, zip,
+    chunk_map, cit, cit_armor, cit_assets, cit_glint, clouds, collisions, command_block,
+    containers, crash, datapack, dynamic_light, effects, environment, extras, fast_hash, fog, font,
+    gfx, graphics, graphics_style, graphics_ui, hdr_calibration, hud, hud_layout, hud_overlays,
+    inventory_effects, java_text, jigsaw_block, json_folder, level_loading, light, lod, logging,
+    menu_blur, mesher, minimap, mipmap, mod_list, model_library, models, multiline_edit,
+    native_emissive, options_file, options_fixes, options_ui, overlay, pack_screen, packs, par,
+    particles, poi_sections, post_chain, potent_sulfur, preedit, providers, screen_draw,
+    screen_effects, sculk, section_mask, settings, shader_options, shader_pack_list, signs, skins,
+    sound_engine, sound_events, sound_preview, spans, split_layout, split_profiles, sprites,
+    streaming, structure_block, tab_list, telemetry, test_block, test_instance_block, testgen,
+    title_edition, trims, ui, vault, weather, widgets, world, worldborder, zip,
 };
 pub mod attack_strength;
 pub mod attribute_updates;

crates/horizon-client/src/crafting.rs

@@ -14,11 +14,34 @@ use horizon_world::nbt::Tag;
 use serde_json::Value;
 use std::{
     collections::{HashMap, HashSet},
-    fs,
-    path::{Path, PathBuf},
+    path::Path,
     sync::Arc,
 };
 
+/// A recipe ingredient of a mod's own kind: the entry named a type in a
+/// namespace outside `minecraft:`, and the loader kept it for this call.
+/// The kind and the JSON the file wrote are here; fill `items` with the
+/// item ids the ingredient matches (item ids only: components are not
+/// checked here; a match-time hook follows separately). Duplicates are
+/// removed keeping first-seen order. The hook may be called more than
+/// once per recipe; the answer must be the same. An unclaimed kind
+/// leaves the list empty and the recipe fails, as an unknown kind does.
+/// API @API:ingredient@.
+#[inline(never)]
+pub fn native_ingredient(
+    kind: &str,
+    data: &serde_json::Map<String, Value>,
+    items: &mut Vec<String>,
+) {
+    let _ = (kind, data, items);
+}
+
+/// Keep first-seen order, drop the rest.
+fn dedup_keep_order(items: &mut Vec<String>) {
+    let mut seen = std::collections::HashSet::new();
+    items.retain(|i| seen.insert(i.clone()));
+}
+
 /// A set of accepted items (expanded from an item, list or tag), and the
 /// items in its `HolderSet` order (`Ingredient.display`'s `TagSlotDisplay`).
 #[derive(Clone, Debug)]
@@ -107,6 +130,14 @@ impl Ingredient {
                     .cloned()
                     .collect()
             }
+            // A mod's own kind: the hook answers with the item list it
+            // matches; a bare type name is minecraft's own, not a mod's.
+            k if k.contains(':') && !k.starts_with("minecraft:") => {
+                let mut list = Vec::new();
+                native_ingredient(k, o, &mut list);
+                dedup_keep_order(&mut list);
+                return (!list.is_empty()).then(|| Self::of(list));
+            }
             _ => return None,
         };
         (!kept.is_empty()).then(|| Self::of(kept))
@@ -1176,48 +1207,6 @@ pub fn recipe_result(v: &Value) -> Option<ItemStack> {
     let template = Template::parse(v)?;
     template.item.is_some().then(|| template.create())
 }
-/// The `.json` files under a `recipe` folder, its subfolders' too, in id
-/// order: each one's path inside the folder without the extension (`a/b`, as a
-/// recipe id has it) and its file. An error when `dir` itself can't be read; a
-/// subfolder or an entry that can't be listed is warned and skipped, as
-/// vanilla's `PathPackResources` keeps what it found.
-pub(crate) fn recipe_files(dir: &Path) -> Result<Vec<(String, PathBuf)>> {
-    let mut files = Vec::new();
-    let mut stack = vec![fs::read_dir(dir)?];
-    while let Some(entries) = stack.pop() {
-        for entry in entries {
-            let entry = match entry {
-                Ok(entry) => entry,
-                Err(e) => {
-                    log::warn!("Horizon: failed to list an entry of {}: {e}", dir.display());
-                    continue;
-                }
-            };
-            let path = entry.path();
-            if path.is_dir() {
-                match fs::read_dir(&path) {
-                    Ok(list) => stack.push(list),
-                    Err(e) => log::warn!("Horizon: failed to list {}: {e}", path.display()),
-                }
-            } else if path.extension().is_some_and(|e| e == "json") {
-                files.push(path);
-            }
-        }
-    }
-    let mut named: Vec<(String, PathBuf)> = files
-        .into_iter()
-        .map(|path| {
-            let inside = path.strip_prefix(dir).unwrap_or(&path).with_extension("");
-            let name: Vec<_> = inside.iter().map(|c| c.to_string_lossy()).collect();
-            (name.join("/"), path)
-        })
-        .collect();
-    // Vanilla lists resources by id, in a map keyed by it
-    // (`FallbackResourceManager`): `crushing` before `crushing/iron`, where
-    // a path's components put the subfolder's file first.
-    named.sort_by(|a, b| a.0.cmp(&b.0));
-    Ok(named)
-}
 /// The type of a recipe the game doesn't craft itself: one outside `minecraft`.
 /// A recipe's whole id from its name in the tables: vanilla's are kept bare
 /// (`oak_planks`), everyone else's whole (`mymod:crusher/iron`).
@@ -1340,14 +1329,14 @@ impl Recipes {
             }
             mods
         };
-        for (name, p) in recipe_files(&root.join("data/minecraft/recipe"))? {
-            sources.push((name, fs::read(&p)?));
+        for file in &crate::json_folder::read(&root.join("data/minecraft/recipe"))?.files {
+            sources.push((file.name.clone(), file.bytes()?.to_vec()));
         }
         for namespace in crate::mod_content::namespaces(root) {
             let dir = root.join(format!("data/{namespace}/recipe"));
             if dir.is_dir() {
-                for (name, p) in recipe_files(&dir)? {
-                    sources.push((format!("{namespace}:{name}"), fs::read(&p)?));
+                for file in &crate::json_folder::read(&dir)?.files {
+                    sources.push((format!("{namespace}:{}", file.name), file.bytes()?.to_vec()));
                 }
             }
         }
@@ -1855,6 +1844,7 @@ impl Recipes {
 mod tests {
     use super::*;
     use crate::banner::BannerLayer;
+    use std::fs;
 
     #[test]
     fn result_count_is_bounded_like_vanilla() {
@@ -1913,6 +1903,23 @@ mod tests {
 
     /// NeoForge's standard ingredient shapes resolve to their flat item
     /// lists; a kind the loader doesn't know still fails the file.
+    #[test]
+    fn an_unclaimed_ingredient_kind_fails_and_dedup_keeps_order() {
+        let items = Items::for_tests(HashMap::new());
+        let json = |s: &str| serde_json::from_str::<Value>(s).unwrap();
+        assert!(
+            Ingredient::parse(&json(r#"{"type":"mymod:aspect","aspect":"fire"}"#), &items,)
+                .is_none()
+        );
+        assert!(
+            Ingredient::parse(&json(r#"{"type":"minecraft:future_shape"}"#), &items,).is_none()
+        );
+        assert!(Ingredient::parse(&json(r#"{"type":"aspect"}"#), &items,).is_none());
+        let mut list = vec!["b".to_string(), "a".to_string(), "b".to_string()];
+        dedup_keep_order(&mut list);
+        assert_eq!(list, vec!["b".to_string(), "a".to_string()]);
+    }
+
     #[test]
     fn neoforge_ingredient_shapes_parse() {
         let mut tags = HashMap::new();

crates/horizon-client/src/entity_nbt.rs

@@ -2343,6 +2343,20 @@ pub fn fireball_to_nbt(
     if let Some(power) = power {
         put(&mut tag, "ExplosionPower", Tag::Byte(power as i8));
     }
+    // Fireball.addAdditionalSaveData: the item it is drawn as, one of the loaded
+    // item or else a fire charge (`setItem` refuses an empty stack and keeps one).
+    if matches!(
+        p.kind,
+        ProjectileKind::LargeFireball { .. } | ProjectileKind::SmallFireball
+    ) {
+        let mut item = tag
+            .get("Item")
+            .and_then(item_from_nbt)
+            .filter(|i| i.count > 0 && &*i.item != "minecraft:air")
+            .unwrap_or_else(|| crate::items::ItemStack::new("minecraft:fire_charge", 1));
+        item.count = 1;
+        put(&mut tag, "Item", item_to_nbt(&item));
+    }
     Some(tag)
 }
 
@@ -4673,6 +4687,61 @@ mod fireball_nbt_tests {
         }
     }
 
+    /// `Fireball.addAdditionalSaveData` / `readAdditionalSaveData`: both fireballs save
+    /// `Item`, a fire charge by default, and a loaded one stays, as one item.
+    #[test]
+    fn a_fireball_saves_its_item() {
+        let item_of = |tag: &Tag| {
+            let item = tag.get("Item").and_then(item_from_nbt).unwrap();
+            (item.item.to_string(), item.count)
+        };
+        for id in ["minecraft:fireball", "minecraft:small_fireball"] {
+            let plain = Tag::compound([
+                ("id", Tag::String(id.into())),
+                ("Pos", doubles(&[0.0, 0.0, 0.0])),
+            ]);
+            let p = fireball_from_nbt(&plain, None).unwrap();
+            let back = fireball_to_nbt(&p, [1, 2, 3, 4], None, Some(&plain)).unwrap();
+            assert_eq!(
+                item_of(&back),
+                ("minecraft:fire_charge".to_owned(), 1),
+                "{id}"
+            );
+            // A loaded item stays, as a single one.
+            let mut loaded = plain.clone();
+            put(
+                &mut loaded,
+                "Item",
+                item_to_nbt(&crate::items::ItemStack::new("minecraft:diamond", 5)),
+            );
+            let p = fireball_from_nbt(&loaded, None).unwrap();
+            let back = fireball_to_nbt(&p, [1, 2, 3, 4], None, Some(&loaded)).unwrap();
+            assert_eq!(item_of(&back), ("minecraft:diamond".to_owned(), 1), "{id}");
+            // An empty one falls back to the fire charge.
+            let mut empty = plain.clone();
+            put(
+                &mut empty,
+                "Item",
+                item_to_nbt(&crate::items::ItemStack::new("minecraft:air", 1)),
+            );
+            let p = fireball_from_nbt(&empty, None).unwrap();
+            let back = fireball_to_nbt(&p, [1, 2, 3, 4], None, Some(&empty)).unwrap();
+            assert_eq!(
+                item_of(&back),
+                ("minecraft:fire_charge".to_owned(), 1),
+                "{id}"
+            );
+        }
+        // The wind charges are not `Fireball`s: they save no item.
+        let wind = Tag::compound([
+            ("id", Tag::String("minecraft:wind_charge".into())),
+            ("Pos", doubles(&[0.0, 0.0, 0.0])),
+        ]);
+        let p = fireball_from_nbt(&wind, None).unwrap();
+        let back = fireball_to_nbt(&p, [1, 2, 3, 4], None, Some(&wind)).unwrap();
+        assert!(back.get("Item").is_none());
+    }
+
     #[test]
     fn thrown_item_projectiles_round_trip_their_flight_item_and_owner() {
         let player = Some([5, 6, 7, 8]);

crates/horizon-client/src/entry.rs

@@ -3,8 +3,18 @@ use crate::{crash, game, logging, ram_limit};
 
 /// Start the game. The executable supplies the allocator and retains the mod API marker.
 pub fn main() {
+    main_with(Default::default());
+}
+
+/// Start the game with trait mods in dispatch order.
+pub fn main_with(mods: crate::mod_api::Mods) {
+    // First: a trait injection into anything below (logging, the crash handler) calls its mod.
+    if crate::mod_api::MODS.set(mods).is_err() {
+        log::warn!("Trait mods already installed; ignoring the second list");
+    }
     horizon_threads::configure_allocator();
     horizon_client::telemetry::mark_start();
+    horizon_client::spans::startup::init(std::time::Instant::now());
     let args: Vec<String> = std::env::args().skip(1).collect();
     let game_args = args.iter().take_while(|a| *a != "--dedicated");
     let help = game_args
@@ -45,8 +55,33 @@ pub fn main() {
         crash::install(home.clone(), side);
         ram_limit::start(&home, side);
     }
+    let renderers = crate::mod_api::mods()
+        .iter()
+        .filter_map(|m| m.render())
+        .collect();
+    if crate::gfx::native_render::install(renderers).is_err() {
+        log::warn!("Trait renderers already installed; keeping the first list");
+    }
+    if horizon_world::native_load_hooks::install(
+        horizon_world::native_load_hooks::NativeLoadHooks {
+            loot_table_load: |id, table| {
+                crate::mod_api::dispatch_loot_table_load(crate::mod_api::mods(), id, table);
+            },
+            modify_default_components: |item, components| {
+                crate::mod_api::dispatch_modify_default_components(
+                    crate::mod_api::mods(),
+                    item,
+                    components,
+                );
+            },
+        },
+    )
+    .is_err()
+    {
+        log::warn!("Native data-load hooks already installed; keeping the first callbacks");
+    }
     raise_open_file_limit();
-    if let Err(error) = game::run() {
+    if let Err(error) = game::run_with() {
         // A bad command line is the caller's mistake, not a crash: no report.
         let usage = error.is::<game::UsageError>();
         log::error!("Horizon: {error}");

crates/horizon-client/src/first_person.rs

@@ -541,6 +541,8 @@ pub struct HandSway {
     pub y_bob: f32,
     pub x_bob_o: f32,
     pub y_bob_o: f32,
+    /// The yaw `tick_wrapped` has followed so far, unwrapped like vanilla's.
+    y_rot: f32,
 }
 impl HandSway {
     /// `LocalPlayer.applyInput` with the player's `getXRot` and `getYRot`.
@@ -548,9 +550,14 @@ impl HandSway {
         self.y_bob_o = self.y_bob;
         self.x_bob_o = self.x_bob;
         self.x_bob += (x_rot - self.x_bob) * 0.5;
-        // Vanilla's yaw runs on without wrapping, so `yRot - yBob` is the short way round. Ours
-        // is kept in -180..180 (a boat turns its rider through it), so take the short way here.
-        self.y_bob += wrap_degrees(y_rot - self.y_bob) * 0.5;
+        self.y_bob += (y_rot - self.y_bob) * 0.5;
+    }
+    /// `tick` for a yaw kept in -180..180 (a boat turns its rider through the wrap). Vanilla's
+    /// yaw runs on without wrapping, so `yRot - yBob` is always the short way round; this
+    /// follows the wrapped yaw by its short steps to give `tick` the same unwrapped yaw.
+    pub fn tick_wrapped(&mut self, x_rot: f32, y_rot: f32) {
+        self.y_rot += wrap_degrees(y_rot - self.y_rot);
+        self.tick(x_rot, self.y_rot);
     }
     /// The degrees the hands turn about X, then Y, before either is drawn:
     /// `(viewXRot - xBob) * 0.1` and `(viewYRot - yBob) * 0.1`, the bobs
@@ -1406,12 +1413,12 @@ mod action_result_tests {
     #[test]
     fn hand_sway_takes_the_short_way_over_the_yaw_wrap() {
         let mut sway = HandSway::default();
-        sway.tick(0.0, 179.0);
+        sway.tick_wrapped(0.0, 179.0);
         for _ in 0..20 {
-            sway.tick(0.0, 179.0);
+            sway.tick_wrapped(0.0, 179.0);
         }
         // The view is still at 179; one tick later it reads -179 (2 degrees on).
-        sway.tick(0.0, -179.0);
+        sway.tick_wrapped(0.0, -179.0);
         let [_, y] = sway.rotation(1.0, 0.0, -179.0);
         assert!(
             y.abs() < 0.5,

crates/horizon-client/src/furnace.rs

@@ -6,7 +6,6 @@ use crate::{
     items::{ItemStack, Items},
     providers::Providers,
 };
-use std::sync::Arc;
 
 /// The furnace methods that read the recipes.
 pub trait FurnaceCooking {
@@ -22,15 +21,15 @@ pub trait FurnaceCooking {
     /// (`Slot.setByPlayer`; partial takes and merges keep the stack).
     fn input_clicked(&mut self, recipes: &Recipes, before: Option<ItemStack>);
     /// One server tick. Returns `Some(lit)` when the LIT block state must change.
-    fn tick(&mut self, recipes: &Recipes, items: &Items, providers: &Providers) -> Option<bool>;
-}
-fn remainder(item: &str) -> Option<&'static str> {
-    match item {
-        "minecraft:lava_bucket" | "minecraft:water_bucket" | "minecraft:milk_bucket" => {
-            Some("minecraft:bucket")
-        }
-        _ => None,
-    }
+    /// `drops` collects what the furnace lets fall at its position
+    /// (`Containers.dropItemStack`): the remainder of a fuel when more of it is left.
+    fn tick(
+        &mut self,
+        recipes: &Recipes,
+        items: &Items,
+        providers: &Providers,
+        drops: &mut Vec<ItemStack>,
+    ) -> Option<bool>;
 }
 impl FurnaceCooking for Furnace {
     fn set_input(&mut self, recipes: &Recipes, stack: Option<ItemStack>) {
@@ -59,7 +58,13 @@ impl FurnaceCooking for Furnace {
             self.set_input(recipes, after);
         }
     }
-    fn tick(&mut self, recipes: &Recipes, items: &Items, providers: &Providers) -> Option<bool> {
+    fn tick(
+        &mut self,
+        recipes: &Recipes,
+        items: &Items,
+        providers: &Providers,
+        drops: &mut Vec<ItemStack>,
+    ) -> Option<bool> {
         let was_lit = self.lit_remaining > 0;
         let mut lit = false;
         if self.lit_remaining > 0 {
@@ -101,16 +106,19 @@ impl FurnaceCooking for Furnace {
                                     (ratio * self.cooking_total as f32).ceil() as i32;
                             }
                             if time > 0 {
+                                // AbstractFurnaceBlockEntity.consumeFuel: the fuel's crafting
+                                // remainder takes the slot once the stack is used up, else
+                                // it is dropped.
                                 if let Some(f) = self.items[1].as_mut() {
-                                    let item = f.item.clone();
+                                    let remainder = items
+                                        .get(&f.item)
+                                        .and_then(|i| i.crafting_remainder.as_deref())
+                                        .map(|r| ItemStack::new(r, 1));
                                     f.count -= 1;
                                     if f.count == 0 {
-                                        self.items[1] = remainder(&item).map(|r| ItemStack {
-                                            item: Arc::from(r),
-                                            count: 1,
-                                            damage: 0,
-                                            extra: None,
-                                        });
+                                        self.items[1] = remainder;
+                                    } else if let Some(remainder) = remainder {
+                                        drops.push(remainder);
                                     }
                                 }
                                 lit = true;
@@ -171,3 +179,98 @@ fn total_time(time: u32, speed: f32) -> i32 {
         time as i32
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{containers::FurnaceKind, items::Items};
+    use horizon_world::loot::PackOverlay;
+    use std::{collections::HashMap, fs};
+
+    /// A furnace with `fuel` x `count` burning `test:ore` into `test:ingot`, over a
+    /// data root holding that one recipe and an item table with two fuels: `test:coal`
+    /// (no remainder) and `test:cell` (a content mod's item that leaves `test:husk`).
+    fn burn(fuel: &str, count: u32) -> (Furnace, Vec<ItemStack>) {
+        let root = std::env::temp_dir().join(format!(
+            "horizon-furnace-remainder-{}-{}-{count}",
+            std::process::id(),
+            fuel.replace(':', "-")
+        ));
+        let _ = fs::remove_dir_all(&root);
+        fs::create_dir_all(root.join("data/minecraft/recipe")).unwrap();
+        fs::write(
+            root.join("data/minecraft/recipe/test_ingot.json"),
+            br#"{"type":"minecraft:smelting","ingredient":"test:ore","result":{"id":"test:ingot"}}"#,
+        )
+        .unwrap();
+        fs::create_dir_all(root.join("data/minecraft/loot_table")).unwrap();
+        let fuel_component =
+            r#"{"minecraft:cooking_fuel": {"burn_time": 200, "speed_multiplier": 1.0}}"#;
+        fs::write(
+            root.join("items.json"),
+            format!(
+                r#"{{"test:ore": {{}}, "test:ingot": {{}}, "test:coal": {fuel_component}, "test:cell": {fuel_component}, "test:husk": {{}}}}"#
+            ),
+        )
+        .unwrap();
+        fs::write(
+            root.join(horizon_items::items::MOD_CRAFT_REMAINDERS),
+            r#"{"test:cell": "test:husk"}"#,
+        )
+        .unwrap();
+        let items = Items::catalog(&root, &PackOverlay::NONE).unwrap();
+        let recipes = Recipes::load(&root, &items, &PackOverlay::NONE).unwrap();
+        let providers = Providers::load(&root);
+        let mut furnace = Furnace {
+            kind: FurnaceKind::Furnace,
+            items: [
+                Some(ItemStack::new("test:ore", 1)),
+                Some(ItemStack::new(fuel, count)),
+                None,
+            ],
+            lit_remaining: 0,
+            lit_total: 0,
+            cooking_timer: 0,
+            cooking_total: 0,
+            speed: 1.0,
+            recipes_used: HashMap::new(),
+        };
+        let mut drops = Vec::new();
+        let lit = furnace.tick(&recipes, &items, &providers, &mut drops);
+        let _ = fs::remove_dir_all(&root);
+        assert_eq!(lit, Some(true), "the fuel lit the furnace");
+        (furnace, drops)
+    }
+
+    fn fuel_slot(furnace: &Furnace) -> Option<(&str, u32)> {
+        furnace.items[1].as_ref().map(|s| (&*s.item, s.count))
+    }
+
+    /// `AbstractFurnaceBlockEntity.consumeFuel`: the last of a fuel with a remainder
+    /// leaves it in the fuel slot.
+    #[test]
+    fn the_last_fuel_leaves_its_remainder_in_the_slot() {
+        let (furnace, drops) = burn("test:cell", 1);
+        assert_eq!(fuel_slot(&furnace), Some(("test:husk", 1)));
+        assert!(drops.is_empty());
+    }
+
+    /// With more of the fuel left, the remainder is dropped at the furnace.
+    #[test]
+    fn a_fuel_still_in_the_stack_drops_its_remainder() {
+        let (furnace, drops) = burn("test:cell", 3);
+        assert_eq!(fuel_slot(&furnace), Some(("test:cell", 2)));
+        assert_eq!(drops, vec![ItemStack::new("test:husk", 1)]);
+    }
+
+    /// A fuel without a remainder leaves nothing.
+    #[test]
+    fn a_fuel_without_a_remainder_leaves_nothing() {
+        let (furnace, drops) = burn("test:coal", 1);
+        assert_eq!(fuel_slot(&furnace), None);
+        assert!(drops.is_empty());
+        let (furnace, drops) = burn("test:coal", 2);
+        assert_eq!(fuel_slot(&furnace), Some(("test:coal", 1)));
+        assert!(drops.is_empty());
+    }
+}

crates/horizon-client/src/game/agent_settings.rs

@@ -86,34 +86,21 @@ impl Game<'_> {
         let server = self
             .control
             .as_ref()
-            .filter(|c| !c.path().as_os_str().is_empty());
-        let mut lines = vec![match server {
-            Some(s) if s.clients() > 0 => {
-                let ago = self
-                    .agent_last
-                    .map(|t| format!(", last command {} s ago", t.elapsed().as_secs()))
-                    .unwrap_or_default();
-                format!(
-                    "Connected: {} agent connection{}{ago}",
-                    s.clients(),
-                    if s.clients() == 1 { "" } else { "s" }
-                )
-            }
-            Some(_) => "Waiting for an agent.".into(),
-            None => "Off: agents can't reach this game.".into(),
-        }];
-        if let Some(s) = server {
-            if self.options.control.is_some() && !self.agent_control_on {
-                lines.push("Opened for this session by the program that started the game.".into());
-            }
-            // The full path is too wide for the page: Copy Connection Details has it.
-            let name = s.path().file_name().unwrap_or_default().to_string_lossy();
-            lines.push(format!(
-                "Socket: {name} (copy the details for its full path)"
-            ));
-        }
-        lines.push("Local only: agents on this computer, never the network.".into());
-        lines
+            .filter(|c| !c.path().as_os_str().is_empty())
+            .map(|s| Socket {
+                clients: s.clients(),
+                name: s
+                    .path()
+                    .file_name()
+                    .unwrap_or_default()
+                    .to_string_lossy()
+                    .into_owned(),
+            });
+        status_lines(
+            server,
+            self.agent_last.map(|t| t.elapsed().as_secs()),
+            self.options.control.is_some() && !self.agent_control_on,
+        )
     }
 
     /// What Copy Connection Details puts on the clipboard: the socket, a horizon-ctl line to try,
@@ -138,3 +125,127 @@ impl Game<'_> {
         )
     }
 }
+
+/// The control socket as the AI Agent page tells of it.
+struct Socket {
+    /// Agents connected now.
+    clients: usize,
+    /// The socket's file name; the full path is too wide for the page (Copy Connection Details
+    /// has it).
+    name: String,
+}
+
+/// The AI Agent page's lines in the selected language: the state, then where agents connect.
+/// `last_command` is the seconds since an agent's last command, `session_only` whether the
+/// program that started the game opened the socket and the player's switch did not.
+fn status_lines(
+    server: Option<Socket>,
+    last_command: Option<u64>,
+    session_only: bool,
+) -> Vec<String> {
+    use horizon_client::lang::{get, tr};
+    let mut lines = vec![match &server {
+        Some(s) if s.clients > 0 => {
+            let (one, many) = match last_command {
+                Some(_) => ("one_ago", "many_ago"),
+                None => ("one", "many"),
+            };
+            let key = format!(
+                "horizon.agent.connected.{}",
+                if s.clients == 1 { one } else { many }
+            );
+            let mut args: Vec<&dyn std::fmt::Display> = Vec::new();
+            if s.clients != 1 {
+                args.push(&s.clients);
+            }
+            if let Some(ago) = &last_command {
+                args.push(ago);
+            }
+            tr(&key, &args)
+        }
+        Some(_) => get("horizon.agent.waiting"),
+        None => get("horizon.agent.off"),
+    }];
+    if let Some(s) = &server {
+        if session_only {
+            lines.push(get("horizon.agent.session_opened"));
+        }
+        lines.push(tr("horizon.agent.socket", &[&s.name]));
+    }
+    lines.push(get("horizon.agent.local_only"));
+    lines
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{Socket, status_lines};
+    use horizon_client::lang::{Language, scoped};
+
+    fn lines(code: &str, clients: usize, ago: Option<u64>, session_only: bool) -> Vec<String> {
+        let socket = Socket {
+            clients,
+            name: "ctl.sock".into(),
+        };
+        let (lines, missed) = scoped(Language::load(&[], code), || {
+            status_lines(Some(socket), ago, session_only)
+        });
+        assert!(missed.is_empty(), "{code}: {missed:?}");
+        lines
+    }
+
+    /// The AI Agent page told its state in English in every language (#1927).
+    #[test]
+    fn agent_page_lines_follow_the_language() {
+        assert_eq!(
+            lines("de_de", 2, Some(5), false),
+            [
+                "Verbunden: 2 Agentenverbindungen, letzter Befehl vor 5 s",
+                "Socket: ctl.sock (Verbindungsdaten kopieren für den vollständigen Pfad)",
+                "Nur lokal: Agenten auf diesem Computer, nie über das Netzwerk.",
+            ]
+        );
+        assert_eq!(
+            lines("pl_pl", 1, None, true),
+            [
+                "Połączono: 1 połączenie agenta",
+                "Otwarte na tę sesję przez program, który uruchomił grę.",
+                "Gniazdo: ctl.sock (skopiuj dane, aby poznać pełną ścieżkę)",
+                "Tylko lokalnie: agenci na tym komputerze, nigdy przez sieć.",
+            ]
+        );
+        let (off, missed) = scoped(Language::load(&[], "fr_fr"), || {
+            status_lines(None, None, false)
+        });
+        assert!(missed.is_empty(), "{missed:?}");
+        assert_eq!(
+            off,
+            [
+                "Désactivé : les agents ne peuvent pas joindre ce jeu.",
+                "Local uniquement : agents sur cet ordinateur, jamais via le réseau.",
+            ]
+        );
+    }
+
+    /// English keeps the sentences it always had: the count, its plural, the time since the last
+    /// command, and the wait for a first agent.
+    #[test]
+    fn agent_page_lines_in_english() {
+        assert_eq!(
+            lines("en_us", 2, Some(5), false)[0],
+            "Connected: 2 agent connections, last command 5 s ago"
+        );
+        assert_eq!(
+            lines("en_us", 1, None, false)[0],
+            "Connected: 1 agent connection"
+        );
+        assert_eq!(
+            lines("en_us", 1, Some(0), false)[0],
+            "Connected: 1 agent connection, last command 0 s ago"
+        );
+        assert_eq!(
+            lines("en_us", 3, None, false)[0],
+            "Connected: 3 agent connections"
+        );
+        assert_eq!(lines("en_us", 0, None, true)[0], "Waiting for an agent.");
+    }
+}

crates/horizon-client/src/game/armor_stands.rs

@@ -4,6 +4,8 @@
 //! the default pose, the hit wobble and humanoid armor layers.
 use super::{Game, InteractTarget};
 use horizon_client::{
+    cit::{Hand, Kind, Rule},
+    cit_armor,
     entities::ArmorStand,
     items::ItemStack,
     mesher::Vertex,
@@ -154,6 +156,27 @@ impl ArmorStandAssets {
     }
 }
 impl Game<'_> {
+    /// OptiFine CIT: the winning armour or elytra rule (`kind`) of the worn `stack`. No lookup
+    /// without CIT rules.
+    pub(super) fn cit_worn_rule(&self, kind: Kind, stack: &ItemStack) -> Option<&Rule> {
+        let rules = &self.pack.item_renderer.cit.as_ref()?.rules;
+        let item_max = self.items().get(&stack.item).map_or(0, |i| i.max_damage);
+        horizon_client::item_render::cit::worn_rule(rules, kind, stack, item_max)
+            .and_then(|i| rules.rules.get(i))
+    }
+    /// The atlas rect of an armour layer `texture` of equipment asset `asset`, or of the one CIT
+    /// armour rule `cit` puts there when the atlas has it.
+    fn armor_layer_rect(
+        &self,
+        cit: Option<&Rule>,
+        asset: &str,
+        kind: &str,
+        texture: &str,
+    ) -> Option<[f32; 4]> {
+        let sprites = &self.gui.atlas.sprites;
+        let r = cit_armor::worn_layer(cit, asset, kind, texture, |s| sprites.get(s))?;
+        Some([r.u0, r.v0, r.u1, r.v1])
+    }
     /// `HumanoidArmorLayer` for the player: (model, texture rect, colour,
     /// overlay) of each worn piece, head to feet.
     pub(super) fn player_armor_layers(&self) -> Vec<(&Part, [f32; 4], u32, u32, bool)> {
@@ -185,7 +208,7 @@ impl Game<'_> {
         )
     }
     /// The layers of the armour items `worn` (with their stacks when known,
-    /// for trims), head to feet.
+    /// for trims and CIT armour rules), head to feet.
     fn armor_layers(
         &self,
         worn: [Option<(&str, Option<&ItemStack>)>; 4],
@@ -240,18 +263,13 @@ impl Game<'_> {
             };
             // Every layer of the asset, the leather overlay too, then the
             // trim layer over the armour.
+            let cit = stack.and_then(|s| self.cit_worn_rule(Kind::Armor, s));
             for (i, (texture, undyed)) in layers.iter().enumerate() {
-                let Some(r) = self.gui.atlas.sprites.get(texture.as_str()) else {
+                let Some(uv) = self.armor_layer_rect(cit, &asset, kind, texture) else {
                     continue;
                 };
                 let color = layer_color(*undyed, stack);
-                out.push((
-                    part,
-                    [r.u0, r.v0, r.u1, r.v1],
-                    color,
-                    if i == 0 { overlay } else { 0 },
-                    false,
-                ));
+                out.push((part, uv, color, if i == 0 { overlay } else { 0 }, false));
                 // The layer's OptiFine emissive overlay, full bright without the glint.
                 if let Some(g) = emissive
                     .overlay(texture)
@@ -999,8 +1017,9 @@ impl Game<'_> {
             apply_pose(&mut layer_poses, &a.pose);
             // EquipmentLayerRenderer: every layer of the asset, the leather overlay
             // too; the shader glint goes on the first layer only (renderShaderGlint).
+            let cit = self.cit_worn_rule(Kind::Armor, stack);
             for (i, (texture, undyed)) in layers.iter().enumerate() {
-                let Some(uv) = uv_of(texture) else {
+                let Some(uv) = self.armor_layer_rect(cit, &asset, kind, texture) else {
                     continue;
                 };
                 let color = layer_color(*undyed, Some(stack));
@@ -1049,6 +1068,7 @@ impl Game<'_> {
         // never crouches or glides, so its wings rest folded.
         self.wings_geometry(
             a.equipment[4].as_ref().map(|s| &*s.item),
+            a.equipment[4].as_ref(),
             None,
             a.small,
             base,
@@ -1296,7 +1316,12 @@ impl Game<'_> {
                     oz / 16.0,
                 ));
             let seed = a.id as i32 + if left { 1 } else { 2 };
-            let state = self.resolve_item(stack, context, Some(&owner), seed);
+            // OptiFine CIT `hand=off` rules: slot 1 is the off hand.
+            let state = if left {
+                self.resolve_item_in_hand(stack, context, Some(&owner), seed, Hand::Off)
+            } else {
+                self.resolve_item(stack, context, Some(&owner), seed)
+            };
             self.submit_item_world(&state, pose, light, out);
         }
         // `CustomHeadLayer`: a worn skull draws the skull model.

crates/horizon-client/src/game/block_entity_ticks.rs

@@ -218,11 +218,17 @@ impl Game<'_> {
         let Some(BlockEntity::Furnace(f)) = self.world.block_entities.get_mut(&pos) else {
             return Ok(());
         };
-        let Some(lit) = f.tick(
+        let mut drops = Vec::new();
+        let lit = f.tick(
             world_recipes!(self),
             world_items!(self),
             self.res.providers(),
-        ) else {
+            &mut drops,
+        );
+        for stack in drops {
+            self.campfire_drop(pos, stack);
+        }
+        let Some(lit) = lit else {
             return Ok(());
         };
         let state = self.world.block(pos.0, pos.1, pos.2);

crates/horizon-client/src/game/boats.rs

@@ -738,84 +738,90 @@ impl Game<'_> {
         // A server player's boat is driven by its client (lan_vehicles.rs).
         let driven = self.guest_vehicles();
         // EntityTickEvent.Post comes once AbstractBoat.tick is over, after the
-        // passes below (lava, ejection, bubbles, contacts): the ticked boats,
-        // in order, kept only while a mod listens (no list without mods).
-        let mut ticked = Vec::new();
-        for i in 0..self.boats.len() {
-            // A mod's hook may have removed boats.
-            if i >= self.boats.len() {
-                break;
-            }
-            let p = self.boats[i].position;
-            if Some(self.boats[i].id) == self.riding
-                || driven.contains(&self.boats[i].id)
-                || !ticking(p.x.floor() as i32, p.z.floor() as i32)
-            {
-                // Its rider's client moves it, but the lead still ticks.
-                if ticking(p.x.floor() as i32, p.z.floor() as i32) && self.remote.is_none() {
-                    let mut b = self.boats[i].clone();
-                    self.tick_boat_leash(&mut b);
-                    self.boats[i] = b;
-                }
-                continue;
-            }
-            let id = self.boats[i].id;
-            let kind = if round.listening() {
-                self.boats[i].entity_type()
-            } else {
-                String::new()
-            };
-            if !self.native_tick_pre_one(&mut round, id, &kind) {
-                continue;
-            }
-            // The hook may have removed boats.
-            let Some(i) = Some(i)
-                .filter(|&i| self.boats.get(i).is_some_and(|b| b.id == id))
-                .or_else(|| self.boats.iter().position(|b| b.id == id))
-            else {
-                continue;
-            };
-            let b = self.boats[i].clone();
-            self.boats[i] = self.tick_boat(b, false);
-            if round.listening() {
-                ticked.push((id, kind));
-            }
-        }
-        // AbstractBoat.tick's applyEffectsFromBlocks, on the server for every
-        // boat, the client-driven ones too.
+        // passes of `boat_server_passes` (lava, ejection, bubbles, contacts),
+        // and before the next boat ticks, as `ServerLevel.tickNonPassenger`.
+        // A pass (lava breaks a boat) or a mod's hook may remove boats: the next one is found
+        // after this one by its id, so none is skipped or ticked twice.
         let mut i = 0;
         while i < self.boats.len() {
-            let p = self.boats[i].position;
-            let skip = Some(self.boats[i].id) == self.riding
-                || round.canceled(self.boats[i].id)
-                || !ticking(p.x.floor() as i32, p.z.floor() as i32);
-            if skip || !self.boat_lava_tick(i) {
-                i += 1;
+            let id = self.boats[i].id;
+            'boat: {
+                let p = self.boats[i].position;
+                if Some(id) == self.riding
+                    || driven.contains(&id)
+                    || !ticking(p.x.floor() as i32, p.z.floor() as i32)
+                {
+                    // Its rider's client moves it, but the lead still ticks.
+                    if ticking(p.x.floor() as i32, p.z.floor() as i32) && self.remote.is_none() {
+                        let mut b = self.boats[i].clone();
+                        self.tick_boat_leash(&mut b);
+                        self.boats[i] = b;
+                    }
+                    self.boat_server_passes(id, &driven, &ticking, &round);
+                    break 'boat;
+                }
+                let kind = if round.listening() {
+                    self.boats[i].entity_type()
+                } else {
+                    String::new()
+                };
+                if !self.native_tick_pre_one(&mut round, id, &kind) {
+                    self.boat_server_passes(id, &driven, &ticking, &round);
+                    break 'boat;
+                }
+                // The hook may have removed boats.
+                let Some(i) = Some(i)
+                    .filter(|&i| self.boats.get(i).is_some_and(|b| b.id == id))
+                    .or_else(|| self.boats.iter().position(|b| b.id == id))
+                else {
+                    break 'boat;
+                };
+                let b = self.boats[i].clone();
+                self.boats[i] = self.tick_boat(b, false);
+                self.boat_server_passes(id, &driven, &ticking, &round);
+                self.native_tick_post_one(&round, id, &kind);
             }
+            i = match self.boats.get(i) {
+                Some(b) if b.id == id => i + 1,
+                _ => self
+                    .boats
+                    .iter()
+                    .position(|b| b.id == id)
+                    .map_or(i, |k| k + 1),
+            };
         }
-        // The rest of AbstractBoat.tick on the server, for every boat: the
-        // passengers of one under water too long get out, and it picks up or
-        // pushes what it touches.
-        for i in 0..self.boats.len() {
-            let p = self.boats[i].position;
-            if !ticking(p.x.floor() as i32, p.z.floor() as i32) || round.canceled(self.boats[i].id)
-            {
-                continue;
-            }
-            // `AbstractBoat.tick` counts submersion on the server even when
-            // its controlling client owns the boat's movement.
-            if driven.contains(&self.boats[i].id) {
-                self.refresh_boat_status(i);
-            }
-            if self.boats[i].out_of_control >= 60.0 {
-                self.eject_boat_riders(i);
-            }
-            self.boat_bubble_tick(i);
-            self.boat_contacts(i);
+    }
+    /// The rest of `AbstractBoat.tick` on the server, for every boat, the
+    /// client-driven ones too: `applyEffectsFromBlocks` (lava breaks a boat
+    /// at once), the passengers of one under water too long get out, and it
+    /// picks up or pushes what it touches.
+    fn boat_server_passes(
+        &mut self,
+        id: u32,
+        driven: &[u32],
+        ticking: &impl Fn(i32, i32) -> bool,
+        round: &super::native_ticks::TickRound,
+    ) {
+        let Some(i) = self.boats.iter().position(|b| b.id == id) else {
+            return;
+        };
+        let p = self.boats[i].position;
+        if !ticking(p.x.floor() as i32, p.z.floor() as i32) || round.canceled(id) {
+            return;
         }
-        for (id, kind) in ticked {
-            self.native_tick_post_one(&round, id, &kind);
+        if Some(id) != self.riding && self.boat_lava_tick(i) {
+            return;
         }
+        // `AbstractBoat.tick` counts submersion on the server even when
+        // its controlling client owns the boat's movement.
+        if driven.contains(&id) {
+            self.refresh_boat_status(i);
+        }
+        if self.boats[i].out_of_control >= 60.0 {
+            self.eject_boat_riders(i);
+        }
+        self.boat_bubble_tick(i);
+        self.boat_contacts(i);
     }
     /// `Entity.canSimulateMovement`: for a boat (`AUTHORITATIVE_SIDE`) a
     /// server leaves the boat its player drives to that player's client, and a

crates/horizon-client/src/game/books.rs

@@ -258,7 +258,7 @@ impl Game<'_> {
             self.remote_close_container();
         }
         self.book = None;
-        self.capture(true);
+        self.capture(self.screen == super::Screen::Playing && !self.screen_over_playing());
     }
     /// `BookEditScreen.saveChanges` and `BookSignScreen`'s Sign and Close:
     /// trailing empty pages dropped, the book in hand updated here and, on a

crates/horizon-client/src/game/campfire.rs

@@ -171,7 +171,7 @@ impl Game<'_> {
 
     /// `Containers.dropItemStack(level, x, y, z, stack)` at the block's
     /// integer position.
-    fn campfire_drop(&mut self, pos: Pos, stack: ItemStack) {
+    pub(super) fn campfire_drop(&mut self, pos: Pos, stack: ItemStack) {
         let at = BlockPos::new(pos.0, pos.1, pos.2);
         for piece in
             horizon_world::level::removal::drop_item_stack(&mut self.world.random, at, stack.count)

crates/horizon-client/src/game/chat.rs

@@ -574,6 +574,8 @@ impl Game<'_> {
     /// last time, when this method can restore it (a command draft only for
     /// /), else with its prefix.
     pub(super) fn open_chat_method(&mut self, prefix: &str) {
+        // handleKeybinds: the number keys select before key.chat and key.command.
+        self.select_queued_hotbar();
         let command = prefix == "/";
         let draft = self
             .ui

crates/horizon-client/src/game/commands.rs

@@ -67,6 +67,8 @@ pub(super) enum Target {
     Tnt(u32),
     /// A falling block, by its entity id (`minecraft:falling_block`).
     Falling(u32),
+    /// A firework rocket, by its entity id (`minecraft:firework_rocket`).
+    Rocket(u32),
     /// An ominous item spawner, by its entity id (`minecraft:ominous_item_spawner`).
     Spawner(u32),
 }
@@ -144,6 +146,7 @@ fn non_player_entity_id(t: Target) -> Option<i32> {
     | Target::Dragon(id)
     | Target::Tnt(id)
     | Target::Falling(id)
+    | Target::Rocket(id)
     | Target::Spawner(id)) = t
     else {
         return None;
@@ -535,6 +538,11 @@ impl Game<'_> {
                 .iter()
                 .find(|f| f.id == id)
                 .map(|f| [f.position.x, f.position.y, f.position.z]),
+            Target::Rocket(id) => self
+                .rockets
+                .iter()
+                .find(|r| r.id == id)
+                .map(|r| [r.position.x, r.position.y, r.position.z]),
             Target::Spawner(id) => self
                 .ominous_spawners
                 .iter()
@@ -588,6 +596,7 @@ impl Game<'_> {
             Target::Dragon(_) => "minecraft:ender_dragon".into(),
             Target::Tnt(_) => "minecraft:tnt".into(),
             Target::Falling(_) => "minecraft:falling_block".into(),
+            Target::Rocket(_) => "minecraft:firework_rocket".into(),
             Target::Spawner(_) => "minecraft:ominous_item_spawner".into(),
         }
     }
@@ -880,6 +889,7 @@ impl Game<'_> {
         }
         candidates.extend(self.tnts.iter().map(|t| Target::Tnt(t.id)));
         candidates.extend(self.falling.iter().map(|f| Target::Falling(f.id)));
+        candidates.extend(self.rockets.iter().map(|r| Target::Rocket(r.id)));
         candidates.extend(self.ominous_spawners.iter().map(|s| Target::Spawner(s.id)));
         candidates
     }
@@ -914,6 +924,7 @@ impl Game<'_> {
             Target::Dragon(id),
             Target::Tnt(id),
             Target::Falling(id),
+            Target::Rocket(id),
             Target::Spawner(id),
         ]
         .into_iter()
@@ -938,6 +949,7 @@ impl Game<'_> {
             Target::Dragon(id) => self.dragon.as_ref().is_some_and(|d| d.id == id),
             Target::Tnt(id) => self.tnts.iter().any(|t| t.id == id),
             Target::Falling(id) => self.falling.iter().any(|f| f.id == id),
+            Target::Rocket(id) => self.rockets.iter().any(|r| r.id == id),
             Target::Spawner(id) => self.ominous_spawners.iter().any(|s| s.id == id),
         }
     }
@@ -1576,6 +1588,12 @@ impl Game<'_> {
                     f.previous = v;
                 }
             }
+            Target::Rocket(id) => {
+                if let Some(r) = self.rockets.iter_mut().find(|r| r.id == id) {
+                    r.position = v;
+                    r.previous = v;
+                }
+            }
             Target::Spawner(id) => {
                 if let Some(s) = self.ominous_spawners.iter_mut().find(|s| s.id == id) {
                     s.position = [v.x, v.y, v.z];
@@ -2080,6 +2098,7 @@ impl Game<'_> {
             Target::Dragon(id) => self.kill_dragon(id),
             Target::Tnt(id) => self.tnts.retain(|t| t.id != id),
             Target::Falling(id) => self.falling.retain(|f| f.id != id),
+            Target::Rocket(id) => self.rockets.retain(|r| r.id != id),
             Target::Spawner(id) => self.ominous_spawners.retain(|s| s.id != id),
         }
         // The orbs marked for removal are gone (Entity.kill removes them).
@@ -2981,6 +3000,7 @@ impl Game<'_> {
     }
     /// `MinecraftServer.setDifficulty(difficulty, true)`.
     pub(super) fn set_difficulty_forced(&mut self, i: u8) {
+        let from = self.ui.difficulty;
         self.ui.difficulty = i;
         // The level data holds the world's difficulty: it survives the
         // reopen, so it follows the command.
@@ -2999,6 +3019,10 @@ impl Game<'_> {
                     locked: self.level.difficulty_locked,
                 }));
         }
+        if from != i {
+            let (from, to) = difficulty_names(from, i);
+            self.native_difficulty_changed(from, to);
+        }
     }
     fn cmd_spawnpoint(&mut self, ctx: &Context) -> R<i32> {
         let targets = if ctx.get("targets").is_some() {
@@ -3725,6 +3749,30 @@ pub(super) fn block_input_matches(
             .all(|(k, v)| s.properties.get(k) == Some(v))
 }
 
+/// The names `native_difficulty_changed` hears for a change from `from` to
+/// `to`: the four difficulties of `options.difficulty.*`, the index kept in
+/// range as the command and the options keep it.
+fn difficulty_names(from: u8, to: u8) -> (&'static str, &'static str) {
+    (
+        DIFFICULTIES[usize::from(from) & 3],
+        DIFFICULTIES[usize::from(to) & 3],
+    )
+}
+
+#[cfg(test)]
+mod difficulty_tests {
+    use super::difficulty_names;
+
+    #[test]
+    fn a_difficulty_change_names_both_ends() {
+        assert_eq!(difficulty_names(0, 3), ("peaceful", "hard"));
+        assert_eq!(difficulty_names(2, 1), ("normal", "easy"));
+        // The four difficulties are the only indexes the command and the
+        // options keep; an index outside them still names one.
+        assert_eq!(difficulty_names(7, 4), ("hard", "peaceful"));
+    }
+}
+
 #[cfg(test)]
 mod summon_tests {
     #[test]
@@ -3756,6 +3804,7 @@ mod look_at_tests {
             Target::Dragon(7),
             Target::Tnt(7),
             Target::Falling(7),
+            Target::Rocket(7),
             Target::Spawner(7),
         ] {
             assert_eq!(non_player_entity_id(t), Some(7), "{t:?}");

crates/horizon-client/src/game/commands/data.rs

@@ -68,7 +68,12 @@ impl Game<'_> {
             .flatten()
     }
     fn entity_nbt_in_level(&mut self, t: Target) -> Option<Tag> {
-        let player_uuid = self.level.player_uuid;
+        // The acting player's own UUID: a guest's turn (the window's player on
+        // the server thread) keeps the world owner's in `level`.
+        let player_uuid = self
+            .lan_acting_uuid
+            .map(horizon_client::lan::playerdata::uuid_ints)
+            .or(self.level.player_uuid);
         Some(match t {
             Target::Guest(_) => {
                 return self
@@ -212,6 +217,11 @@ impl Game<'_> {
                 );
                 crate::game::persist::with_raw(tag, raw)
             }
+            Target::Rocket(id) => {
+                let uuid = self.uuid_for(id);
+                let r = self.rockets.iter().find(|r| r.id == id)?;
+                r.to_nbt(uuid, player_uuid, self.persist.raw.get(&id))
+            }
             Target::Spawner(id) => {
                 let s = self.ominous_spawners.iter().find(|s| s.id == id)?;
                 let [x, y, z] = s.position;
@@ -842,6 +852,8 @@ impl Game<'_> {
             Some(Target::Tnt(id))
         } else if self.falling.iter().any(|f| f.id == id) {
             Some(Target::Falling(id))
+        } else if self.rockets.iter().any(|r| r.id == id) {
+            Some(Target::Rocket(id))
         } else if self.ominous_spawners.iter().any(|s| s.id == id) {
             Some(Target::Spawner(id))
         } else {

crates/horizon-client/src/game/control.rs

@@ -10,7 +10,27 @@ use std::{
 };
 use winit::{event::MouseButton, keyboard::KeyCode};
 
+/// The control protocol's version (`docs/api/stability.md`): before 1.0 an
+/// addition makes the next patch and a breaking change the next line.
+const PROTOCOL: &str = "0.1.0";
+
+/// The command groups the game serves, as `help` chains them: what `hello` reports as its features.
+const FEATURES: &[&str] = &[
+    "game", "station", "blocks", "lan", "friends", "render", "sculk", "agent", "ui", "options",
+    "events", "saves", "pad",
+];
+
+/// `hello`: the protocol the socket speaks, the game's release and the command groups it serves.
+fn hello() -> Value {
+    json!({
+        "protocol": PROTOCOL,
+        "release": horizon_core::release::VERSION,
+        "features": FEATURES,
+    })
+}
+
 const HELP: &[&str] = &[
+    "hello                          the control protocol's version, the game's release and the command groups it serves",
     "status                         game, player, streaming and renderer state",
     "simulation                     authoritative projectiles in the owner's level",
     "server-hold on|off             hold simulation and player packets at a control-fixture barrier",
@@ -36,7 +56,7 @@ const HELP: &[&str] = &[
     "type TEXT                      type into the open chat box (key enter tap sends)",
     "chat-log [N]                   the newest N chat messages (default 10)",
     "options [PAGE]                 open the options (video sound controls keybinds mouse chat accessibility language font packs mods graphics graphics-advanced graphics-hdr)",
-    "stats [reset]                  frame-time summary since the last reset",
+    "stats [reset] [raw]            frame-time summary since the last reset (raw: every frame time too)",
     "narration                      the narrator's status and the last messages it was asked to say",
     "bench SECONDS                  reset stats, wait, then reply with the summary",
     "fly X1 Y1 Z1 X2 Y2 Z2 SECONDS [PITCH [raw]]  fly the camera along a line at constant speed, then reply with the frame summary (raw: every frame time too)",
@@ -355,6 +375,7 @@ impl Game<'_> {
                 Ok(Some(json!({ "ok": true, "sides": r.section_sides() })))
             }
             "sculk" => Ok(Some(self.sculk_command(&words)?)),
+            "hello" => Ok(Some(hello())),
             "status" => Ok(Some(self.control_status())),
             "stall" => {
                 let millis: u64 = arg(1)?.parse()?;
@@ -859,8 +880,13 @@ impl Game<'_> {
                 })))
             }
             "stats" => {
-                let summary = self.summary_with_passes();
-                if words.get(1) == Some(&"reset") {
+                let mut summary = self.summary_with_passes();
+                if words[1..].contains(&"raw") {
+                    summary["frame_ms"] = self.frame_stats.frame_millis().into();
+                    summary["cpu_ms"] = self.frame_stats.cpu_millis().into();
+                    summary["gpu_ms"] = self.frame_stats.gpu_millis().into();
+                }
+                if words[1..].contains(&"reset") {
                     self.frame_stats.reset();
                 }
                 Ok(Some(summary))
@@ -1403,6 +1429,25 @@ fn key_code(name: &str) -> Option<KeyCode> {
 mod tests {
     use super::*;
 
+    #[test]
+    fn hello_names_the_protocol_the_release_and_the_command_groups() {
+        let reply = hello();
+        assert_eq!(reply["release"], horizon_core::release::VERSION);
+        let protocol = reply["protocol"].as_str().unwrap();
+        let parts: Vec<_> = protocol.split('.').collect();
+        assert!(
+            parts.len() == 3 && parts.iter().all(|p| p.parse::<u32>().is_ok()),
+            "{protocol}"
+        );
+        let features = reply["features"].as_array().unwrap();
+        assert!(!features.is_empty());
+        let mut names: Vec<_> = features.iter().filter_map(Value::as_str).collect();
+        assert_eq!(names.len(), features.len());
+        names.sort_unstable();
+        names.dedup();
+        assert_eq!(names.len(), features.len(), "a group is named twice");
+    }
+
     #[test]
     fn taps_and_ups_always_release_their_key() {
         for line in ["key shift tap", "key shift up", "key  Shift  up"] {

crates/horizon-client/src/game/creatures.rs

@@ -21,6 +21,7 @@ use horizon_client::{
         farm::Climate,
         spawning::{self, BiomeFacts},
     },
+    mod_api::NativeLootDrops,
     particles::{ParticleOptions, ParticleType},
     projectiles::{Hit, Projectile, ProjectileKind, ProjectileWorld},
     text::Text,
@@ -487,14 +488,15 @@ impl Game<'_> {
         }
     }
     /// `LivingEntity.hurtArmor` -> `LivingEntity.doHurtEquipment`, from the hit
-    /// `MobEvent::ArmorHurt` reported: every worn piece that wears when its
-    /// wearer is hurt loses `max(1, damage / 4)` durability, Unbreaking
-    /// applied, and at its maximum the slot empties and the equipment-break
-    /// event goes out (`LivingEntity.entityEventForEquipmentBreak`: 49 to 52
-    /// for the armour, 65 for the body). A fire hit leaves a fire-resistant
-    /// piece alone (`ItemStack.canBeHurtBy`).
+    /// `MobEvent::ArmorHurt` reported. Only `Horse` overrides `hurtArmor` for a
+    /// mob, and its override asks for the BODY slot alone, so the body piece is
+    /// the only one this wears: it loses `max(1, damage / 4)` durability,
+    /// Unbreaking applied, and at its maximum the slot empties and the break
+    /// event goes out (`LivingEntity.entityEventForEquipmentBreak`: 65 for the
+    /// body — 49 to 52 are the four armour slots, which only a player's own
+    /// pieces reach). A fire hit leaves a fire-resistant piece alone
+    /// (`ItemStack.canBeHurtBy`).
     fn hurt_mob_armor(&mut self, id: u32, damage: f32, kind: horizon_client::mobs::DamageKind) {
-        use horizon_client::mobs::drops;
         use horizon_world::player_inventory::EquipmentSlot;
         if damage <= 0.0 {
             return;
@@ -503,7 +505,6 @@ impl Game<'_> {
             return;
         };
         let at = [m.position.x, m.position.y, m.position.z];
-        let body_armour = drops::head_is_body(m.species());
         let amount = ((damage / 4.0) as u32).max(1);
         let name = damage_type(kind, false);
         let fire = self
@@ -513,9 +514,15 @@ impl Game<'_> {
             .id(name)
             .is_some_and(|d| self.motion.health.damage.in_tag(d, "minecraft:is_fire"));
         // A piece's maximum, or none when it may not lose durability at all.
+        // `doHurtEquipment` starts from the item's `equippable` component
+        // (`Equippable equippable = item.get(DataComponents.EQUIPPABLE)`), so a
+        // damageable item with no such component — a sword put in a horse's body
+        // slot by `/item replace` — never wears; `equip_damage_on_hurt` alone
+        // cannot say that, since it defaults to true when the component is absent.
         fn wearable(me: &Game<'_>, stack: &ItemStack, fire: bool, name: &str) -> Option<u32> {
             let info = me.res.items().get(&stack.item)?;
-            if !info.equip_damage_on_hurt
+            if info.equip_slot.is_none()
+                || !info.equip_damage_on_hurt
                 || info.max_damage == 0
                 || !horizon_client::stations::is_damageable(me.res.items(), stack)
                 || (fire && me.res.items().resists_fire(stack, name))
@@ -524,66 +531,39 @@ impl Game<'_> {
             }
             Some(info.max_damage)
         }
-        let mut broke: Vec<i8> = Vec::new();
-        // The four armour slots, then the body slot (`extra.head`).
-        let event_of = horizon_client::mobs::item_break::equipment_break_event;
-        for (index, slot) in [
-            (0usize, EquipmentSlot::Head),
-            (1, EquipmentSlot::Chest),
-            (2, EquipmentSlot::Legs),
-            (3, EquipmentSlot::Feet),
-        ] {
-            let Some(m) = self.mobs.iter().find(|m| m.id == id) else {
-                return;
-            };
-            let Some(stack) = m.extra.armor[index].clone() else {
-                continue;
-            };
-            let Some(max) = wearable(self, &stack, fire, name) else {
-                continue;
-            };
-            let loss = self.durability_loss(&stack, amount);
-            if loss == 0 {
-                continue;
-            }
-            let lost = stack.damage + loss;
+        let Some(body) = self
+            .mobs
+            .iter()
+            .find(|m| m.id == id)
+            .and_then(|m| m.item_by_slot(EquipmentSlot::Body))
+        else {
+            return;
+        };
+        let Some(max) = wearable(self, &body, fire, name) else {
+            return;
+        };
+        let loss = self.durability_loss(&body, amount);
+        if loss == 0 {
+            return;
+        }
+        let lost = body.damage + loss;
+        let broke = {
             let Some(m) = self.mobs.iter_mut().find(|m| m.id == id) else {
                 return;
             };
             if lost >= max {
-                m.extra.armor[index] = None;
-                broke.push(event_of(slot));
-            } else if let Some(worn) = m.extra.armor[index].as_mut() {
-                worn.damage = lost;
+                m.extra.head = None;
+                m.extra.body_damage = 0;
+                true
+            } else {
+                m.extra.body_damage = lost as i32;
+                false
             }
-        }
-        if body_armour {
-            let body = self
-                .mobs
-                .iter()
-                .find(|m| m.id == id)
-                .and_then(|m| m.item_by_slot(EquipmentSlot::Body));
-            if let Some(body) = body
-                && let Some(max) = wearable(self, &body, fire, name)
-            {
-                let loss = self.durability_loss(&body, amount);
-                if loss > 0 {
-                    let lost = body.damage + loss;
-                    let Some(m) = self.mobs.iter_mut().find(|m| m.id == id) else {
-                        return;
-                    };
-                    if lost >= max {
-                        m.extra.head = None;
-                        m.extra.body_damage = 0;
-                        broke.push(event_of(EquipmentSlot::Body));
-                    } else {
-                        m.extra.body_damage = lost as i32;
-                    }
-                }
-            }
-        }
-        for event in broke {
+        };
+        if broke {
             // LivingEntity.onEquippedItemBroken through the level's broadcast.
+            let event =
+                horizon_client::mobs::item_break::equipment_break_event(EquipmentSlot::Body);
             self.lan_entity_event(id as i32, event, at);
         }
     }
@@ -1498,7 +1478,7 @@ impl Game<'_> {
         }
         let kind = super::native_hooks::mob_kind(m);
         let table = drops::death_loot_table(m, death.mob_drops).filter(|t| loot.has_table(t));
-        let context = super::native_hooks::NativeLootDrops {
+        let context = NativeLootDrops {
             table: table.as_deref().unwrap_or_default(),
             dimension: self.dim.id(),
             origin: [m.position.x, m.position.y, m.position.z],
@@ -6475,14 +6455,7 @@ impl Game<'_> {
             // ShulkerBulletRenderer: the tumbling bullet model, then a larger
             // translucent copy of it (colour 0x26FFFFFF); always 15 block light.
             if matches!(a.kind, ProjectileKind::ShulkerBullet { .. }) {
-                static BULLET: std::sync::OnceLock<Option<horizon_client::mobs::Part>> =
-                    std::sync::OnceLock::new();
-                let model = BULLET.get_or_init(|| {
-                    horizon_client::mobs::load_model(
-                        &self.options.resources,
-                        "minecraft:shulker_bullet#main",
-                    )
-                });
+                let model = &self.entity_models.shulker_bullet;
                 if let (Some(model), Some(r)) =
                     (model, atlas.sprites.get("entity/shulker/spark").copied())
                 {
@@ -6534,14 +6507,7 @@ impl Game<'_> {
             }
             // WitherSkullRenderer: the skull model facing its flight.
             if let Some(dangerous) = super::wither::skull_kind(a) {
-                static SKULL: std::sync::OnceLock<Option<horizon_client::mobs::Part>> =
-                    std::sync::OnceLock::new();
-                let model = SKULL.get_or_init(|| {
-                    horizon_client::mobs::load_model(
-                        &self.options.resources,
-                        "minecraft:wither_skull#main",
-                    )
-                });
+                let model = &self.entity_models.wither_skull;
                 let tex = if dangerous {
                     "entity/wither/wither_invulnerable"
                 } else {

crates/horizon-client/src/game/dedicated.rs

@@ -257,6 +257,16 @@ fn forwarding_secret(online: bool) -> Result<Option<Vec<u8>>> {
     Ok(Some(secret))
 }
 
+/// `MinecraftServer.runServer`'s overload warning for a server `behind` its
+/// schedule, in milliseconds and in ticks of `tick`.
+fn overload_warning(behind: Duration, tick: Duration) -> String {
+    format!(
+        "Can't keep up! Is the server overloaded? Running {}ms or {} ticks behind",
+        behind.as_millis(),
+        behind.as_nanos() / tick.as_nanos().max(1)
+    )
+}
+
 /// Log4j's console pattern: `[HH:mm:ss] [thread/LEVEL]: message`.
 pub(super) fn log(level: &str, message: &str) {
     log_from("Server thread", level, message);
@@ -502,6 +512,13 @@ const LEGACY_PRESET_NAMES: [(&str, horizon_client::save::WorldPreset); 2] = [
 
 /// server.properties' line for `server.toml`'s `max_view_distance` (horizon-server writes it).
 const FAR_PROPERTY: &str = "horizon-max-view-distance";
+/// A dedicated server logs a tick slower than this, in milliseconds, with
+/// its spans, unless `HORIZON_SPIKES` names another threshold: five ticks'
+/// worth, a stall players feel as rubber-banding.
+pub(super) const SLOW_TICK_MS: f32 = 250.0;
+/// `MinecraftServer.OVERLOADED_WARNING_INTERVAL_NANOS` plus 100 ticks: the
+/// "Can't keep up!" warning comes at most this often.
+const OVERLOAD_WARNING_INTERVAL: Duration = Duration::from_secs(15);
 /// server.properties' line for `server.toml`'s `admin_feedback_to_ops` (horizon-server writes it).
 const ADMIN_FEEDBACK_PROPERTY: &str = "horizon-admin-feedback-to-ops";
 
@@ -618,6 +635,8 @@ struct ServerState {
     /// View and simulation distance, and the player limit, for the report.
     view: (u32, u32),
     max_players: usize,
+    /// The mutable `gamemode` server property (`DedicatedServer.gameMode`).
+    game_mode: i32,
 }
 
 /// The dedicated-only commands' replies vanilla sends with `broadcast`
@@ -985,6 +1004,7 @@ impl Game<'_> {
             broadcast_console: props.broadcast_console_to_ops,
             broadcast_rcon: props.broadcast_rcon_to_ops,
             op_level: props.op_permission_level,
+            game_mode: props.game_mode,
             report: None,
             view: (
                 props.view_distance.clamp(2, 32) as u32,
@@ -1000,6 +1020,7 @@ impl Game<'_> {
         self.fns.permission = Some(props.function_permission_level.clamp(0, 4) as u8);
         let watchdog = Watchdog::start(props.max_tick_time);
         let mut braked = Instant::now();
+        let mut overload_warned: Option<Instant> = None;
         while !state.stop {
             let tick_start = Instant::now();
             if let Some(watchdog) = &watchdog {
@@ -1089,7 +1110,17 @@ impl Game<'_> {
                 far.brake(mspt, host.hub.config.view_distance);
             }
             state.ticked(Instant::now());
-            self.wait_for_next_server_tick(&mut next, paused);
+            // MinecraftServer.runServer: a server more than a second's ticks
+            // behind skips them and says so, at most every 15 seconds.
+            if let Some(behind) = self.wait_for_next_server_tick(&mut next, paused)
+                && overload_warned.is_none_or(|at| at.elapsed() >= OVERLOAD_WARNING_INTERVAL)
+            {
+                overload_warned = Some(Instant::now());
+                log(
+                    "WARN",
+                    &overload_warning(behind, self.clock.tick_duration()),
+                );
+            }
         }
         if let Some(watchdog) = &watchdog {
             watchdog.running.store(false, Ordering::Relaxed);
@@ -1975,7 +2006,7 @@ fn png_size(bytes: &[u8]) -> Option<(u32, u32)> {
 
 #[cfg(test)]
 mod tests {
-    use super::{capture_log, log, log_from, panic_message};
+    use super::{capture_log, log, log_from, overload_warning, panic_message};
     use std::{
         fs,
         io::{self, BufRead, BufReader, Read, Write},
@@ -1983,6 +2014,16 @@ mod tests {
         time::{SystemTime, UNIX_EPOCH},
     };
 
+    /// Vanilla's words, with how far behind the server is in milliseconds and in whole ticks.
+    #[test]
+    fn the_overload_warning_reads_as_vanilla_s() {
+        let tick = std::time::Duration::from_millis(50);
+        assert_eq!(
+            overload_warning(std::time::Duration::from_millis(13_027), tick),
+            "Can't keep up! Is the server overloaded? Running 13027ms or 260 ticks behind"
+        );
+    }
+
     /// A `panic!("literal")` carries a `&str`, a formatted one a `String`; anything else is
     /// named as unknown, so the crash line is never empty.
     #[test]

crates/horizon-client/src/game/dedicated/management.rs

@@ -3,7 +3,7 @@
 //! `AllowlistService`, `BanlistService`, `IpBanlistService` and `OperatorService` on the running server's lists. Players are found as
 //! `MinecraftPlayerListService.getUser` finds them, each change is logged as `JsonRpcLogger` logs it, and the
 //! players a change shuts out are disconnected. The supervisor answers with the lists, from their files.
-use super::{ServerState, log};
+use super::{GAME_MODES, ServerState, log};
 use crate::game::Game;
 use horizon_client::{
     command::vanilla::DIFFICULTIES,
@@ -70,6 +70,25 @@ impl Game<'_> {
                 self.store_property("motd", value.to_owned());
                 return json!({ "value": value });
             }
+            "serversettings/game_mode" => {
+                return json!({ "value": GAME_MODES[state.game_mode as usize] });
+            }
+            "serversettings/game_mode/set" => {
+                let Some(value) = body["value"].as_str() else {
+                    return json!({ "error": "game mode must be a string" });
+                };
+                let Some(index) = GAME_MODES.iter().position(|name| *name == value) else {
+                    return json!({ "error": format!("unknown game mode {value:?}") });
+                };
+                rpc(format!(
+                    "Update game mode from '{}' to '{}'",
+                    GAME_MODES[state.game_mode as usize], value
+                ));
+                self.store_property("gamemode", value.to_owned());
+                state.game_mode = index as i32;
+                self.set_default_game_mode(state.game_mode);
+                return json!({ "value": GAME_MODES[state.game_mode as usize] });
+            }
             "serversettings/difficulty" => {
                 return json!({ "value": DIFFICULTIES[self.level.difficulty_id() as usize] });
             }

crates/horizon-client/src/game/dispenser.rs

@@ -13,6 +13,8 @@ use horizon_client::{
     particles::{ParticleOptions, ParticleType},
     projectiles::{Projectile, ProjectileKind},
 };
+// Its old home, for mixin code that names it here.
+pub(super) use horizon_client::mod_api::NativeDispensed;
 use horizon_core::{
     geometry::{Aabb, Direction, Vec3},
     position::BlockPos,
@@ -99,10 +101,6 @@ fn shrink(mut stack: ItemStack) -> Option<ItemStack> {
 /// A dispenser's answer: the slot's new content and the level event played.
 type Dispensed = (Option<ItemStack>, i32);
 
-/// A dispenser hook's answer: the slot's remainder (None empties it) and the
-/// level event to play, `CLICK` (1000), `FAIL` (1001) or 0 for none.
-pub(super) type NativeDispensed = (Option<ItemStack>, i32);
-
 /// None keeps vanilla's behaviour; an explicit empty remainder consumes the stack.
 fn mod_dispensed(answer: Option<NativeDispensed>) -> Option<Dispensed> {
     answer.map(|(left, event)| (left.filter(|stack| stack.count > 0), event))

crates/horizon-client/src/game/dragon.rs

@@ -1814,8 +1814,9 @@ impl Game<'_> {
                     {
                         y -= 1.0;
                     }
+                    let id = self.take_entity_id();
                     self.breath_clouds.push(Breath {
-                        id: 0,
+                        id,
                         at: [x, y.floor() + 1.0, z],
                         radius: 5.0,
                         age: 0,
@@ -2291,8 +2292,9 @@ impl Game<'_> {
         );
         // assignDirectionalMovement: the direction times the acceleration power 0.1.
         let velocity = Vec3::new(v.x * 0.1, v.y * 0.1, v.z * 0.1);
+        let id = self.take_entity_id();
         self.dragon_fireballs.push(DragonFireball {
-            id: 0,
+            id,
             position: at,
             previous: at,
             velocity,
@@ -2338,8 +2340,9 @@ impl Game<'_> {
                 ))
             });
             if hit_block || hit_player || b.age > 600 {
+                let id = self.take_entity_id();
                 self.breath_clouds.push(Breath {
-                    id: 0,
+                    id,
                     at: [next.x, next.y, next.z],
                     radius: 3.0,
                     age: 0,

crates/horizon-client/src/game/enchant_effects.rs

@@ -89,7 +89,17 @@ impl Game<'_> {
     /// `ItemStack.hurtAndBreak` for the player's `stack`: the wear Unbreaking
     /// leaves, and `ItemDurabilityTrigger` when some is left (`applyDamage`).
     pub(super) fn wear(&mut self, stack: &ItemStack, amount: u32) -> u32 {
-        let loss = self.durability_loss(stack, amount);
+        let mut loss = self.durability_loss(stack, amount);
+        // The mods hear a server player's wear once Unbreaking has had its say,
+        // and may change it or stop it.
+        if loss > 0
+            && let (Some(uuid), Some(name)) = (self.lan_acting_uuid, self.lan_acting_name.clone())
+        {
+            let mut points = loss as i32;
+            let mut cancel = false;
+            self.native_item_damaged(uuid, &name, &stack.item, &mut points, &mut cancel);
+            loss = if cancel { 0 } else { points.max(0) as u32 };
+        }
         if loss > 0 {
             self.trigger_item_durability(stack, stack.damage + loss);
         }

crates/horizon-client/src/game/end.rs

@@ -1302,8 +1302,10 @@ impl Game<'_> {
             target
         };
         let survive = self.world.random.next_int_bound(5).unwrap_or(0) > 0;
+        self.next_entity += 1;
+        let id = self.next_entity;
         self.end.eyes.push(EyeOfEnder {
-            id: 0,
+            id,
             position: start,
             previous: start,
             velocity: glam::DVec3::ZERO,
@@ -1571,7 +1573,7 @@ impl Game<'_> {
             // A gateway keeps the item in its level (teleportSameDimension
             // moves it): it doesn't leave, so no native_entity_leave_level.
             self.dropped.remove(i);
-            self.forget_entity(id);
+            self.detach_entity(id);
             tag
         } else if let Some(i) = self.mobs.iter().position(|m| m.id == id) {
             let mut tag = self.mob_tree_nbt(i);
@@ -1594,7 +1596,7 @@ impl Game<'_> {
             }
             self.mobs.retain(|m| !gone.contains(&m.id));
             for g in gone {
-                self.forget_entity(g);
+                self.detach_entity(g);
             }
             tag
         } else if let Some(i) = self.creatures.projectiles.iter().position(|p| p.id == id) {

crates/horizon-client/src/game/entity.rs

@@ -0,0 +1,308 @@
+//! `Entity`: what every kind in the game's entity lists answers to, so a system
+//! can treat them alike and only write down where vanilla's kinds differ.
+//!
+//! Default methods follow vanilla's `Entity`; a kind overrides one only where
+//! its vanilla class does. [`EntityHandle`] names one entity by list and index,
+//! so a system can walk handles and reach each entity after other borrows of
+//! `Game` end. The walk allocates nothing and dispatch is static: hot paths pay
+//! no vtable. A new kind is one line in `entity_lists!` and one `impl Entity`.
+
+use super::{FallingBlock, Game};
+use super::{
+    boats::Boat, fireworks::Rocket, minecarts::Minecart, tnt::PrimedTnt, trident::ThrownTrident,
+};
+use horizon_client::entities::{ArmorStand, ExperienceOrb, ItemEntity};
+use horizon_client::mobs::Mob;
+use horizon_client::projectiles::Projectile;
+use horizon_core::geometry::{Aabb, Direction, Vec3};
+use horizon_core::position::BlockPos;
+use horizon_world::{level::data::PushReaction, piston_push};
+
+pub(super) trait Entity {
+    fn position(&self) -> Vec3;
+    fn position_mut(&mut self) -> &mut Vec3;
+    fn velocity_mut(&mut self) -> &mut Vec3;
+    fn bounds(&self) -> Aabb;
+
+    fn on_ground(&self) -> bool {
+        false
+    }
+    /// `Entity.maxUpStep`.
+    fn get_step_height(&self) -> f32 {
+        0.0
+    }
+    fn is_alive(&self) -> bool {
+        true
+    }
+    /// `Entity.isSupportedBy`.
+    fn is_supported_by(&self, _pos: BlockPos) -> bool {
+        false
+    }
+    /// `Entity.getPistonPushReaction`.
+    fn get_piston_push_reaction(&self) -> PushReaction {
+        PushReaction::PushPull
+    }
+    /// `Entity.move(MoverType.PISTON, …)` once the movement is resolved.
+    fn move_by_piston(&mut self, movement: Vec3) {
+        let position = self.position_mut();
+        *position = position.add_vector(movement);
+    }
+    /// `PistonMovingBlockEntity.causeBounce`: a slime block sets the velocity
+    /// along the movement axis.
+    fn piston_slime_bounce(&mut self, movement: Direction) {
+        let velocity = self.velocity_mut();
+        *velocity = piston_push::bounce_velocity(movement, *velocity);
+    }
+}
+
+/// The fields every kind stores under the same names.
+macro_rules! stored_motion {
+    () => {
+        fn position(&self) -> Vec3 {
+            self.position
+        }
+        fn position_mut(&mut self) -> &mut Vec3 {
+            &mut self.position
+        }
+        fn velocity_mut(&mut self) -> &mut Vec3 {
+            &mut self.velocity
+        }
+    };
+}
+
+/// The game's lists of entities, in the order systems walk them. Hands them to
+/// `$then`, so one list drives the handles and every typed dispatch.
+macro_rules! entity_lists {
+    ($then:ident, $($args:tt)*) => {
+        $crate::game::entity::$then! {
+            ($($args)*)
+            Mob: mobs,
+            Item: dropped,
+            Boat: boats,
+            Cart: carts,
+            ArmorStand: armor_stands,
+            Tnt: tnts,
+            Falling: falling,
+            Orb: orbs,
+            Projectile: creatures.projectiles,
+            Rocket: rockets,
+            Trident: tridents,
+        }
+    };
+}
+pub(crate) use entity_lists;
+
+macro_rules! define_entity_handles {
+    (() $($kind:ident: $($list:ident).+,)*) => {
+        /// One entity, by list and index.
+        #[derive(Clone, Copy, Hash, PartialEq, Eq)]
+        pub(super) enum EntityHandle {
+            $($kind(usize),)*
+        }
+
+        impl Game<'_> {
+            /// Every entity's handle: lengths read now, nothing allocated, and
+            /// no borrow of `Game` held, so the caller can change it mid-walk.
+            pub(super) fn entity_handles(&self) -> impl Iterator<Item = EntityHandle> + use<> {
+                std::iter::empty()
+                    $(.chain((0..self$(.$list)+.len()).map(EntityHandle::$kind)))*
+            }
+        }
+    };
+}
+pub(crate) use define_entity_handles;
+
+entity_lists!(define_entity_handles,);
+
+macro_rules! entity_borrow {
+    (shared, $place:expr) => {
+        &$place
+    };
+    (exclusive, $place:expr) => {
+        &mut $place
+    };
+}
+pub(crate) use entity_borrow;
+
+macro_rules! match_entity {
+    (($borrow:ident, $entity:ident, $game:expr, $handle:expr, $body:expr)
+     $($kind:ident: $($list:ident).+,)*) => {
+        match $handle {
+            $($crate::game::entity::EntityHandle::$kind(i) => {
+                let $entity = $crate::game::entity::entity_borrow!($borrow, $game$(.$list)+[i]);
+                $body
+            })*
+        }
+    };
+}
+pub(crate) use match_entity;
+
+/// Runs `$body` with `$entity` bound to the handle's entity, as its own type:
+/// one match, each arm compiled for its kind, so nothing goes through a vtable.
+macro_rules! with_entity {
+    ($game:expr, $handle:expr, $entity:ident => $body:expr) => {
+        $crate::game::entity::entity_lists!(match_entity, shared, $entity, $game, $handle, $body)
+    };
+}
+pub(super) use with_entity;
+
+/// [`with_entity`], with the entity mutable.
+macro_rules! with_entity_mut {
+    ($game:expr, $handle:expr, $entity:ident => $body:expr) => {
+        $crate::game::entity::entity_lists!(match_entity, exclusive, $entity, $game, $handle, $body)
+    };
+}
+pub(super) use with_entity_mut;
+
+impl Entity for Mob {
+    stored_motion!();
+    fn bounds(&self) -> Aabb {
+        Mob::bounds(self)
+    }
+    fn on_ground(&self) -> bool {
+        self.on_ground
+    }
+    fn get_step_height(&self) -> f32 {
+        self.kind.step_height as f32
+    }
+    fn is_alive(&self) -> bool {
+        !self.removed && self.alive()
+    }
+    fn is_supported_by(&self, pos: BlockPos) -> bool {
+        self.supporting == Some([pos.x, pos.y, pos.z])
+    }
+}
+
+impl Entity for ItemEntity {
+    stored_motion!();
+    fn bounds(&self) -> Aabb {
+        ItemEntity::bounds(self)
+    }
+    fn on_ground(&self) -> bool {
+        self.on_ground
+    }
+    fn move_by_piston(&mut self, movement: Vec3) {
+        self.position = self.position.add_vector(movement);
+        // Entity.move(MoverType.PISTON): onGround only if the push was down.
+        if movement.y != 0.0 {
+            self.on_ground = movement.y < 0.0;
+        }
+    }
+    fn piston_slime_bounce(&mut self, movement: Direction) {
+        ItemEntity::piston_slime_bounce(self, movement);
+    }
+}
+
+impl Entity for ExperienceOrb {
+    stored_motion!();
+    fn bounds(&self) -> Aabb {
+        ExperienceOrb::bounds(self)
+    }
+    fn on_ground(&self) -> bool {
+        self.on_ground
+    }
+    fn move_by_piston(&mut self, movement: Vec3) {
+        self.position = self.position.add_vector(movement);
+        if movement.y != 0.0 {
+            self.on_ground = movement.y < 0.0;
+        }
+    }
+    fn piston_slime_bounce(&mut self, movement: Direction) {
+        self.velocity = piston_push::bounce_velocity(movement, self.velocity);
+        self.on_ground = false;
+    }
+}
+
+impl Entity for Boat {
+    stored_motion!();
+    fn bounds(&self) -> Aabb {
+        Boat::bounds(self)
+    }
+    fn on_ground(&self) -> bool {
+        self.on_ground
+    }
+}
+
+impl Entity for Minecart {
+    stored_motion!();
+    fn bounds(&self) -> Aabb {
+        Minecart::bounds(self)
+    }
+    fn on_ground(&self) -> bool {
+        self.on_ground
+    }
+}
+
+impl Entity for ArmorStand {
+    stored_motion!();
+    fn bounds(&self) -> Aabb {
+        ArmorStand::bounds(self)
+    }
+    fn on_ground(&self) -> bool {
+        self.on_ground
+    }
+    /// `ArmorStand.getPistonPushReaction`: a marker is ignored.
+    fn get_piston_push_reaction(&self) -> PushReaction {
+        if self.marker {
+            PushReaction::IgnoreEntity
+        } else {
+            PushReaction::PushPull
+        }
+    }
+}
+
+impl Entity for PrimedTnt {
+    stored_motion!();
+    fn bounds(&self) -> Aabb {
+        PrimedTnt::bounds(self)
+    }
+    fn on_ground(&self) -> bool {
+        self.on_ground
+    }
+    fn piston_slime_bounce(&mut self, movement: Direction) {
+        self.velocity = piston_push::bounce_velocity(movement, self.velocity);
+        // Leave the ground so the next tick does not apply the on-ground
+        // Y * -0.5 friction that cancels the launch.
+        self.on_ground = false;
+    }
+}
+
+impl Entity for FallingBlock {
+    stored_motion!();
+    fn bounds(&self) -> Aabb {
+        horizon_client::falling_block::bounds(self.position)
+    }
+}
+
+impl Entity for Projectile {
+    stored_motion!();
+    fn bounds(&self) -> Aabb {
+        Projectile::bounds(self)
+    }
+    fn move_by_piston(&mut self, movement: Vec3) {
+        self.position = self.position.add_vector(movement);
+        self.needs_sync = true;
+    }
+    fn piston_slime_bounce(&mut self, movement: Direction) {
+        self.velocity = piston_push::bounce_velocity(movement, self.velocity);
+        self.needs_sync = true;
+    }
+}
+
+impl Entity for Rocket {
+    stored_motion!();
+    fn bounds(&self) -> Aabb {
+        Rocket::bounds(self)
+    }
+}
+
+impl Entity for ThrownTrident {
+    stored_motion!();
+    fn bounds(&self) -> Aabb {
+        let p = self.position;
+        Aabb::new(
+            Vec3::new(p.x - 0.25, p.y, p.z - 0.25),
+            Vec3::new(p.x + 0.25, p.y + 0.5, p.z + 0.25),
+        )
+    }
+}

crates/horizon-client/src/game/fangs.rs

@@ -28,11 +28,7 @@ impl Game<'_> {
 
     pub(super) fn insert_fangs(&mut self, id: u32, at: [f64; 3], yaw: f32, delay: i32, owner: u32) {
         if self.fangs.model.is_none() {
-            self.fangs.model = horizon_client::mobs::load_model(
-                &self.options.resources,
-                "minecraft:evoker_fangs#main",
-            )
-            .map(Arc::new);
+            self.fangs.model = self.entity_models.evoker_fangs.clone();
         }
         self.fangs.list.push(Fangs {
             id,

crates/horizon-client/src/game/fireworks.rs

@@ -29,7 +29,8 @@ enum RocketHit {
 }
 
 pub(super) struct Rocket {
-    /// The entity id a server tracks it by (0 until it is tracked).
+    /// Its entity id: from the entity counter on the server, the server's on
+    /// a client.
     pub id: u32,
     pub(super) position: Vec3,
     pub(super) previous: Vec3,
@@ -223,8 +224,10 @@ impl Game<'_> {
         let lifetime = 10 * (1 + i32::from(flight))
             + r.next_int_bound(6).unwrap_or(0)
             + r.next_int_bound(7).unwrap_or(0);
+        // An id from the entity counter at once, so a command can name it.
+        self.next_entity += 1;
         Rocket {
-            id: 0,
+            id: self.next_entity,
             position: at,
             previous: at,
             velocity,

crates/horizon-client/src/game/fishing.rs

@@ -98,6 +98,22 @@ impl Game<'_> {
         if &*stack.item != "minecraft:fishing_rod" {
             return false;
         }
+        // The mods hear a server player's cast or reel-in first.
+        if self.player.is_some()
+            && let (Some(uuid), Some(name)) = (self.lan_acting_uuid, self.lan_acting_name.clone())
+        {
+            let state = match &self.hook {
+                None => 0,
+                Some(h) if matches!(h.state, State::Hooked(_)) => 4,
+                Some(h) if h.nibble > 0 => 2,
+                Some(_) => 3,
+            };
+            let mut cancel = false;
+            self.native_player_fish(uuid, &name, state, &mut cancel);
+            if cancel {
+                return true;
+            }
+        }
         let Some(p) = self.player.as_ref() else {
             return false;
         };
@@ -419,6 +435,19 @@ impl Game<'_> {
                     }
                 }
             } else {
+                // The mods hear a server player's fish bite, and may call it
+                // off: the wait starts over.
+                if let (Some(uuid), Some(name)) =
+                    (self.lan_acting_uuid, self.lan_acting_name.clone())
+                {
+                    let mut cancel = false;
+                    self.native_player_fish(uuid, &name, 1, &mut cancel);
+                    if cancel {
+                        h.time_until_lured = 0;
+                        h.time_until_hooked = 0;
+                        return;
+                    }
+                }
                 let pitch =
                     1.0 + (self.world.random.next_float() - self.world.random.next_float()) * 0.4;
                 self.audio.play(

crates/horizon-client/src/game/hand.rs

@@ -205,6 +205,94 @@ impl Game<'_> {
         self.attack_ticks = 0;
         self.hand_strength.reset();
     }
+    /// `Minecraft.tick`'s `pick`, then `handleKeybinds`' number keys: the
+    /// tick's clicks act on what the item held before the keys picked (a
+    /// spear's 4.5 blocks), with the item the keys select (attribute
+    /// swapping a spear's reach onto a mace).
+    pub(super) fn pick_tick_targets(&mut self) {
+        self.tick_hit = Some(self.pick());
+        self.tick_mob = None;
+        let mob = match self.active_attack_range() {
+            Some(range) => self.attack_range_pick(&range),
+            None => None,
+        };
+        self.tick_mob = Some(mob.unwrap_or_else(|| self.mob_hit()));
+        self.select_queued_hotbar();
+    }
+    /// `handleKeybinds`' number keys (`keyHotbarSlots[i].consumeClick`).
+    pub(super) fn select_queued_hotbar(&mut self) {
+        for slot in std::mem::take(&mut self.hotbar_presses) {
+            self.selected = slot;
+        }
+    }
+    /// The tick's clicks are done: later picks follow the crosshair again.
+    pub(super) fn release_tick_targets(&mut self) {
+        self.tick_hit = None;
+        self.tick_mob = None;
+    }
+    /// `Minecraft.startAttack` on an entity: a main-hand item with an
+    /// `attack_range` attacks only a hit inside it.
+    pub(super) fn held_range_allows(&self, distance: f64) -> bool {
+        let range = self.held().and_then(|stack| {
+            self.pack
+                .item_renderer
+                .models
+                .components(&horizon_client::item_render::stack_view(stack))
+                .get("minecraft:attack_range")
+                .cloned()
+        });
+        range.is_none_or(|r| attack_range_contains(&r, distance, self.creative))
+    }
+    /// `LocalPlayer.raycastHitResult`'s item (`getActiveItem`: the one in
+    /// use, else the main hand's) `attack_range` component.
+    fn active_attack_range(&self) -> Option<serde_json::Value> {
+        let active = self
+            .using
+            .and_then(|(slot, _)| self.inventory.get(slot).and_then(Option::as_ref))
+            .or_else(|| self.held())?;
+        self.pack
+            .item_renderer
+            .models
+            .components(&horizon_client::item_render::stack_view(active))
+            .get("minecraft:attack_range")
+            .cloned()
+    }
+    /// `AttackRange.getClosesetHit` against the mobs `mob_hit` can pick
+    /// (`EntitySelector.CAN_BE_PICKED`), as `raycastHitResult` reads it: the
+    /// nearest mob hit within the item's reach; no mob when the clip met a
+    /// block within the block reach (`getHitEntitiesAlong`'s block result,
+    /// kept by `filterHitResult`); `None` on a miss, where the plain pick
+    /// decides.
+    fn attack_range_pick(&self, range: &serde_json::Value) -> Option<Option<(usize, f64)>> {
+        let eye = v3(self.eye_position()?);
+        let look = v3(super::view_vector(self.yaw, self.pitch));
+        let reach = attack_reach(range, self.creative);
+        let camera = self.remote_camera_id();
+        let boxes: Vec<(usize, Aabb)> = (self.mobs.iter().enumerate())
+            .filter(|(_, m)| !m.removed && Some(m.id) != self.riding && Some(m.id) != camera)
+            .map(|(i, m)| (i, m.bounds()))
+            .collect();
+        let clip = |from: Vec3, to: Vec3| {
+            let length = from.distance_squared(to).sqrt();
+            let d = to.subtract(from).scale(1.0 / length);
+            (length > 0.0)
+                .then(|| self.clip_ray([from.x, from.y, from.z], [d.x, d.y, d.z], length))
+                .flatten()
+                .map(|hit| Vec3::new(hit.point[0], hit.point[1], hit.point[2]))
+        };
+        let movement = self.known_player_movement();
+        let nearest = super::spear::hits_in_reach(&boxes, eye, look, movement, reach, clip)
+            .into_iter()
+            .map(|(i, at)| (i, eye.distance_squared(at).sqrt()))
+            .reduce(|a, b| if b.1 < a.1 { b } else { a });
+        if nearest.is_some() {
+            return Some(nearest);
+        }
+        let to = eye.add_vector(look.scale(f64::from(reach.1) + movement.dot(look).max(0.0)));
+        clip(eye, to)
+            .is_some_and(|block| eye.distance_squared(block) <= self.block_reach.powi(2))
+            .then_some(None)
+    }
     /// The attack and use part of `Minecraft.tick` for the local player:
     /// attack clicks since the last tick and the held attack button.
     pub(super) fn tick_local_hand(&mut self) -> Result<()> {
@@ -216,11 +304,10 @@ impl Game<'_> {
             // (scripts under --control hold buttons without grabbing it).
             let down = self.left;
             let ticks = self.clicks.destroying.ticks;
-            // Minecraft.hitResult is picked once per frame: a creative break
-            // does not move the use that follows it past the broken block.
-            if use_clicks > 0 && attack_clicks > 0 {
-                self.tick_hit = Some(self.pick());
-            }
+            // Minecraft.hitResult is picked once per tick, before the number
+            // keys: a creative break does not move the use that follows it
+            // past the broken block.
+            self.pick_tick_targets();
             let mut world = GameHands {
                 game: self,
                 error: None,
@@ -229,7 +316,7 @@ impl Game<'_> {
             let error = world.error.take();
             self.clicks = clicks;
             if let Some(e) = error {
-                self.tick_hit = None;
+                self.release_tick_targets();
                 return Err(e);
             }
             // Use clicks follow the attack clicks within the tick, against
@@ -245,7 +332,7 @@ impl Game<'_> {
                     break;
                 }
             }
-            self.tick_hit = None;
+            self.release_tick_targets();
             used?;
             // A tick of breaking: the hit sound every fourth tick and the
             // cracking particles.
@@ -267,8 +354,10 @@ impl Game<'_> {
                 }
             }
         } else {
-            // Minecraft.tick: a screen keeps the attack from starting.
+            // Minecraft.tick: a screen keeps the attack from starting, and
+            // opening it released the keys (`KeyMapping.releaseAll`).
             self.clicks.miss_time = 10000;
+            self.hotbar_presses.clear();
         }
         let d = &self.clicks.destroying;
         self.mining = d.active.then_some(Mining {
@@ -385,7 +474,7 @@ impl Game<'_> {
     pub(super) fn tick_hand(&mut self) {
         // LocalPlayer.applyInput (the camera is the player's own).
         if self.player.is_some() {
-            self.sway.tick(self.pitch, self.yaw);
+            self.sway.tick_wrapped(self.pitch, self.yaw);
         }
         self.swing.tick();
         let main = self.inventory[self.selected].clone();

crates/horizon-client/src/game/integrated.rs

@@ -17,6 +17,7 @@ use super::{
     world_loading::{WorldLoader, WorldRequest},
 };
 use horizon_client::level_loading::{STATUS_RADIUS, Stage};
+use horizon_client::spans::startup;
 use horizon_client::{
     Result,
     audio::Audio,
@@ -685,9 +686,11 @@ impl Game<'_> {
         self.native_server_about_to_start(false);
         self.native_lifecycle_open_started();
         // `load_world`, with the world `serve` started preparing.
-        self.join_world_rest()?;
+        startup::time("server.wait_rest", || self.join_world_rest())?;
         self.perf.world_opening();
+        let open_step = startup::step("server.open_world");
         self.finish_open_world(opening.world?.finish()?)?;
+        drop(open_step);
         if let Some(sync) = opening.sync {
             sync.adopt(&self.pack_files());
         }
@@ -751,7 +754,9 @@ impl Game<'_> {
             guest_commands: false,
             force_game_mode: false,
         };
-        self.lan_host(settings, net, config, None)?;
+        startup::time("server.lan_host", || {
+            self.lan_host(settings, net, config, None)
+        })?;
         let commands = self.allow_commands();
         let pipe = {
             let host = self
@@ -781,7 +786,7 @@ impl Game<'_> {
         view.start(Stage::LoadInitialChunks, 0);
         view.finish(Stage::LoadInitialChunks);
         let _ = ready.send(Ok((pipe, self.level.name.clone())));
-        self.settle_spawn()
+        startup::time("server.settle_spawn", || self.settle_spawn())
     }
 
     /// `MinecraftServer.stopServer`: the players are saved and sent away,
@@ -1141,7 +1146,9 @@ fn serve(
         world,
         sync: preload_sync_data(&options.resources),
     };
-    let mut server = match server_game(res, pack, options, settings) {
+    let mut server = match startup::time("server.game_new", || {
+        server_game(res, pack, options, settings)
+    }) {
         Ok(server) => server,
         Err(e) => {
             // The world's session lock is let go before the failure is told.