From 5fa08d20d6a5ca43c3bfe2f1d558dfc85552b85c Mon Sep 17 00:00:00 2001
From: Matt Borgerson <contact@mborgerson.com>
Date: Sat, 21 Oct 2023 16:46:41 -0700
Subject: [PATCH] nv2a: Scale Z by full depth range in inverse viewport
 transform

---
 hw/xbox/nv2a/pgraph.c | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

diff --git a/hw/xbox/nv2a/pgraph.c b/hw/xbox/nv2a/pgraph.c
index 9d9247feca..a134a2a661 100644
--- a/hw/xbox/nv2a/pgraph.c
+++ b/hw/xbox/nv2a/pgraph.c
@@ -28,6 +28,9 @@
 #include "ui/xemu-settings.h"
 #include "qemu/fast-hash.h"
 
+const float f16_max = 511.9375f;
+const float f24_max = 1.0E30;
+
 static NV2AState *g_nv2a;
 GloContext *g_nv2a_context_render;
 GloContext *g_nv2a_context_display;
@@ -3493,10 +3496,6 @@ DEF_METHOD(NV097, CLEAR_SURFACE)
         GLint gl_clear_stencil;
         GLfloat gl_clear_depth;
 
-        /* FIXME: Put these in some lookup table */
-        const float f16_max = 511.9375f;
-        const float f24_max = 1.0E30;
-
         switch(pg->surface_shape.zeta_format) {
         case NV097_SET_SURFACE_FORMAT_ZETA_Z16: {
             uint16_t z = clear_zstencil & 0xFFFF;
@@ -4180,8 +4179,18 @@ static void pgraph_shader_update_constants(PGRAPHState *pg,
                     *(float*)&pg->regs[NV_PGRAPH_FOGPARAM1]);
     }
 
-    float zclip_max = *(float*)&pg->regs[NV_PGRAPH_ZCLIPMAX];
-    float zclip_min = *(float*)&pg->regs[NV_PGRAPH_ZCLIPMIN];
+    /* FIXME: Handle NV_PGRAPH_ZCLIPMIN, NV_PGRAPH_ZCLIPMAX */
+    float zmax;
+    switch (pg->surface_shape.zeta_format) {
+    case NV097_SET_SURFACE_FORMAT_ZETA_Z16:
+        zmax = pg->surface_shape.z_format ? f16_max : (float)0xFFFF;
+        break;
+    case NV097_SET_SURFACE_FORMAT_ZETA_Z24S8:
+        zmax = pg->surface_shape.z_format ? f24_max : (float)0xFFFFFF;
+        break;
+    default:
+        assert(0);
+    }
 
     if (fixed_function) {
         /* update lighting constants */
@@ -4238,19 +4247,15 @@ static void pgraph_shader_update_constants(PGRAPHState *pg,
 
         float m11 = 0.5 * (pg->surface_binding_dim.width/aa_width);
         float m22 = -0.5 * (pg->surface_binding_dim.height/aa_height);
-        float m33 = zclip_max - zclip_min;
+        float m33 = zmax;
         float m41 = *(float*)&pg->vsh_constants[NV_IGRAPH_XF_XFCTX_VPOFF][0];
         float m42 = *(float*)&pg->vsh_constants[NV_IGRAPH_XF_XFCTX_VPOFF][1];
-        float m43 = zclip_min;
-        if (m33 == 0.0) {
-            m33 = 1.0;
-        }
 
         float invViewport[16] = {
             1.0/m11, 0, 0, 0,
             0, 1.0/m22, 0, 0,
             0, 0, 1.0/m33, 0,
-            -1.0+m41/m11, 1.0+m42/m22, -m43/m33, 1.0
+            -1.0+m41/m11, 1.0+m42/m22, 0, 1.0
         };
 
         if (binding->inv_viewport_loc != -1) {
@@ -4284,7 +4289,7 @@ static void pgraph_shader_update_constants(PGRAPHState *pg,
     }
 
     if (binding->clip_range_loc != -1) {
-        glUniform2f(binding->clip_range_loc, zclip_min, zclip_max);
+        glUniform2f(binding->clip_range_loc, 0, zmax);
     }
 
     /* Clipping regions */