fix(render): use original MSH UV scale

2 files changed, 29 insertions, 9 deletions

diff --git a/adapters/fparkan-render-vulkan/src/asset_mesh.rs b/adapters/fparkan-render-vulkan/src/asset_mesh.rs
index 2cf340f..d6689b9 100644
--- a/adapters/fparkan-render-vulkan/src/asset_mesh.rs
+++ b/adapters/fparkan-render-vulkan/src/asset_mesh.rs
@@ -94,19 +94,23 @@ pub fn project_msh_to_static_mesh(
     let vertices = model
         .positions
         .iter()
-        .map(|position| VulkanStaticVertex {
+        .enumerate()
+        .map(|(index, position)| VulkanStaticVertex {
             position: [
                 (position[0] - center_x) * scale,
                 (position[2] - center_z) * scale,
             ],
             color: [0.82, 0.72, 0.31],
-            // The exact fixed-point normalization of Res5 is still under
-            // disassembly. Until then the asset viewer uses its documented XZ
-            // planar projection, rather than inventing a scale for raw i16 UV0.
-            uv: [
-                (position[0] - center_x) / extent + 0.5,
-                (position[2] - center_z) / extent + 0.5,
-            ],
+            // Iron3D stores Res5 UV0 as signed fixed point with 1/1024 units.
+            // Models that omit this optional stream retain the static viewer's
+            // XZ planar fallback instead of receiving fabricated raw UV values.
+            uv: model.uv0.as_ref().and_then(|uv0| uv0.get(index)).map_or(
+                [
+                    (position[0] - center_x) / extent + 0.5,
+                    (position[2] - center_z) / extent + 0.5,
+                ],
+                |uv| [f32::from(uv[0]) / 1024.0, f32::from(uv[1]) / 1024.0],
+            ),
         })
         .collect();
 
@@ -165,4 +169,20 @@ mod tests {
         assert_eq!(mesh.vertices[2].position, [0.8, -0.8]);
         assert_eq!(mesh.vertices[3].position, [-0.8, 0.8]);
     }
+
+    #[test]
+    fn projects_packed_uv0_using_documented_fixed_point_scale() {
+        let mut source = model(
+            vec![[-2.0, 0.0, -1.0], [2.0, 0.0, -1.0], [-2.0, 0.0, 3.0]],
+            vec![0, 1, 2],
+            vec![batch(0, 3, 0)],
+        );
+        source.uv0 = Some(vec![[1024, -512], [0, 2048], [-1024, 512]]);
+
+        let mesh = project_msh_to_static_mesh(&source).expect("representable MSH");
+
+        assert_eq!(mesh.vertices[0].uv, [1.0, -0.5]);
+        assert_eq!(mesh.vertices[1].uv, [0.0, 2.0]);
+        assert_eq!(mesh.vertices[2].uv, [-1.0, 0.5]);
+    }
 }
diff --git a/docs/rendering/renderer_truth_table.md b/docs/rendering/renderer_truth_table.md
index 61396ac..eec54d3 100644
--- a/docs/rendering/renderer_truth_table.md
+++ b/docs/rendering/renderer_truth_table.md
@@ -29,7 +29,7 @@
 
 ## Current repository status
 
-- Реальный Vulkan в репозитории имеет smoke triangle path и узкий static asset bridge: `fparkan-vulkan-smoke --model-root <GOG_ROOT> --model-archive system.rlb --model-name MTCHECK.MSH --texture-root <GOG_ROOT> --texture-archive Textures.lib --texture-name DEFAULT.0` загружает validated original MSH, разворачивает batch `base_vertex`, нормализует XZ viewer plane, выполняет real indexed draw и загружает decoded TEXM mip-0 в device-local image. Image переходит в sampling layout, записывается в `set=0,binding=0` combined image sampler и sampled fragment shader-ом. Для static viewer UV сейчас XZ-planar: parser сохраняет raw packed `Res5` UV0, но его fixed-point scale ещё не доказан. Это не WEAR/MAT0, exact material, terrain или gameplay renderer.
+- Реальный Vulkan в репозитории имеет smoke triangle path и узкий static asset bridge: `fparkan-vulkan-smoke --model-root <GOG_ROOT> --model-archive system.rlb --model-name MTCHECK.MSH --texture-root <GOG_ROOT> --texture-archive Textures.lib --texture-name DEFAULT.0` загружает validated original MSH, разворачивает batch `base_vertex`, нормализует XZ viewer plane, выполняет real indexed draw и загружает decoded TEXM mip-0 в device-local image. Image переходит в sampling layout, записывается в `set=0,binding=0` combined image sampler и sampled fragment shader-ом. `Res5` UV0 декодируется как signed fixed point `int16 / 1024.0`; XZ-planar UV остаётся только fallback для модели без optional stream. Это не WEAR/MAT0, exact material, terrain или gameplay renderer.
 - `apps/fparkan-game` сейчас выдает `render-planning` JSON report поверх
   synthetic window descriptor и `VulkanPlanningBackend`.
 - `apps/fparkan-viewer` сейчас inspection-only CLI и не открывает live Vulkan