Fix: Provide CPU mesh processing with MaterialBindingId

crates/bevy_pbr/src/render/mesh.rs

@@ -837,12 +837,43 @@ pub struct RenderMeshInstanceGpuQueues(Parallel<RenderMeshInstanceGpuQueue>);
 pub struct MeshesToReextractNextFrame(MainEntityHashSet);
 
 impl RenderMeshInstanceShared {
-    fn from_components(
+    /// A gpu builder will provide the mesh instance id
+    /// during `RenderMeshGpuBuilder::update`.
+    ///
+    /// Therefore, this does not need to be queried.
+    #[inline]
+    fn for_gpu_building(
         previous_transform: Option<&PreviousGlobalTransform>,
         mesh: &Mesh3d,
         tag: Option<&MeshTag>,
         not_shadow_caster: bool,
         no_automatic_batching: bool,
+    ) -> Self {
+        Self::for_cpu_building(
+            previous_transform,
+            mesh,
+            tag,
+            default(),
+            not_shadow_caster,
+            no_automatic_batching,
+        )
+    }
+
+    /// Build a struct with common properties between gpu and cpu builders for cpu builders.
+    ///
+    /// Unlike the gpu builder, the cpu builder does not have an equivalent
+    /// [`RenderMeshGpuBuilder::update`]. Therefore, we need to have
+    /// the [`MaterialBindingId`] ahead of time.
+    ///
+    /// Otherwise, a mesh with a handle to a base color texture will all appear identical
+    /// based on the most recently inserted mesh.
+    fn for_cpu_building(
+        previous_transform: Option<&PreviousGlobalTransform>,
+        mesh: &Mesh3d,
+        tag: Option<&MeshTag>,
+        material_bindings_index: MaterialBindingId,
+        not_shadow_caster: bool,
+        no_automatic_batching: bool,
     ) -> Self {
         let mut mesh_instance_flags = RenderMeshInstanceFlags::empty();
         mesh_instance_flags.set(RenderMeshInstanceFlags::SHADOW_CASTER, !not_shadow_caster);
@@ -858,8 +889,7 @@ impl RenderMeshInstanceShared {
         RenderMeshInstanceShared {
             mesh_asset_id: mesh.id(),
             flags: mesh_instance_flags,
-            // This gets filled in later, during `RenderMeshGpuBuilder::update`.
-            material_bindings_index: default(),
+            material_bindings_index,
             lightmap_slab_index: None,
             tag: tag.map_or(0, |i| **i),
         }
@@ -1305,6 +1335,8 @@ pub struct ExtractMeshesSet;
 /// [`MeshUniform`] building.
 pub fn extract_meshes_for_cpu_building(
     mut render_mesh_instances: ResMut<RenderMeshInstances>,
+    mesh_material_ids: Res<RenderMaterialInstances>,
+    render_material_bindings: Res<RenderMaterialBindings>,
     render_visibility_ranges: Res<RenderVisibilityRanges>,
     mut render_mesh_instance_queues: Local<Parallel<Vec<(Entity, RenderMeshInstanceCpu)>>>,
     meshes_query: Extract<
@@ -1358,10 +1390,22 @@ pub fn extract_meshes_for_cpu_building(
                 transmitted_receiver,
             );
 
-            let shared = RenderMeshInstanceShared::from_components(
+            let mesh_material = mesh_material_ids.mesh_material(MainEntity::from(entity));
+
+            let material_bindings_index = (mesh_material != DUMMY_MESH_MATERIAL.untyped())
+                .then(|| {
+                    render_material_bindings
+                        .get(&mesh_material)
+                        .copied()
+                        .unwrap_or_default()
+                })
+                .unwrap_or_default();
+
+            let shared = RenderMeshInstanceShared::for_cpu_building(
                 previous_transform,
                 mesh,
                 tag,
+                material_bindings_index,
                 not_shadow_caster,
                 no_automatic_batching,
             );
@@ -1566,7 +1610,7 @@ fn extract_mesh_for_gpu_building(
         transmitted_receiver,
     );
 
-    let shared = RenderMeshInstanceShared::from_components(
+    let shared = RenderMeshInstanceShared::for_gpu_building(
         previous_transform,
         mesh,
         tag,