HDR: fog hides light sources, animated sprites keep shining, the vignette keeps the lift

A light source's mark ignored fog: fully fogged, it stood out, through water since #6471.
A sprite that shines all over took a threshold from one frame of its animation, so other
frames' pixels dropped out. The vignette's darkest corners lost the lift at once.

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

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

@@ -329,7 +329,10 @@ fn shadow_color(in: Out) -> vec4<f32> {
     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)));
+    // Fog hides a light source 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;
+    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));

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

@@ -53,7 +53,7 @@ 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.

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

@@ -463,8 +463,12 @@ fn solid_finish(in: TerrainOut, texel: vec4<f32>, color: vec4<f32>) -> vec4<f32>
         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 {
+            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;
+            emissive = hdr_mark(tier, y * (1.0 - fogged));
         }
     }
     if in.emissive_layer != 0xffffffffu {