Extract mesh view layouts logic (#13266)

Copied almost verbatim from the volumetric fog PR

# Objective

- Managing mesh view layouts is complicated

## Solution

- Extract it to it's own struct
- This was done as part of #13057 and is copied almost verbatim. I
wanted to keep this part of the PR it's own atomic commit in case we
ever have to revert fog or run a bisect. This change is good whether or
not we have volumetric fog.

Co-Authored-By: @pcwalton

crates/bevy_pbr/src/render/mesh.rs

@@ -33,15 +33,13 @@ use bevy_render::{
     texture::{BevyDefault, DefaultImageSampler, ImageSampler, TextureFormatPixelInfo},
     view::{
         prepare_view_targets, GpuCulling, RenderVisibilityRanges, ViewTarget, ViewUniformOffset,
-        ViewVisibility, VisibilityRange, VISIBILITY_RANGES_STORAGE_BUFFER_COUNT,
+        ViewVisibility, VisibilityRange,
     },
     Extract,
 };
 use bevy_transform::components::GlobalTransform;
 use bevy_utils::{tracing::error, tracing::warn, Entry, HashMap, Parallel};
 
-#[cfg(debug_assertions)]
-use bevy_utils::warn_once;
 use bytemuck::{Pod, Zeroable};
 use nonmax::{NonMaxU16, NonMaxU32};
 use static_assertions::const_assert_eq;
@@ -234,6 +232,7 @@ impl Plugin for MeshRenderPlugin {
 
             render_app
                 .insert_resource(indirect_parameters_buffer)
+                .init_resource::<MeshPipelineViewLayouts>()
                 .init_resource::<MeshPipeline>();
         }
 
@@ -1034,7 +1033,8 @@ fn collect_meshes_for_gpu_building(
 
 #[derive(Resource, Clone)]
 pub struct MeshPipeline {
-    view_layouts: [MeshPipelineViewLayout; MeshPipelineViewLayoutKey::COUNT],
+    /// A reference to all the mesh pipeline view layouts.
+    pub view_layouts: MeshPipelineViewLayouts,
     // This dummy white texture is to be used in place of optional StandardMaterial textures
     pub dummy_white_gpu_image: GpuImage,
     pub clustered_forward_buffer_binding_type: BufferBindingType,
@@ -1065,18 +1065,12 @@ impl FromWorld for MeshPipeline {
             Res<RenderDevice>,
             Res<DefaultImageSampler>,
             Res<RenderQueue>,
+            Res<MeshPipelineViewLayouts>,
         )> = SystemState::new(world);
-        let (render_device, default_sampler, render_queue) = system_state.get_mut(world);
+        let (render_device, default_sampler, render_queue, view_layouts) =
+            system_state.get_mut(world);
         let clustered_forward_buffer_binding_type = render_device
             .get_supported_read_only_binding_type(CLUSTERED_FORWARD_STORAGE_BUFFER_COUNT);
-        let visibility_ranges_buffer_binding_type = render_device
-            .get_supported_read_only_binding_type(VISIBILITY_RANGES_STORAGE_BUFFER_COUNT);
-
-        let view_layouts = generate_view_layouts(
-            &render_device,
-            clustered_forward_buffer_binding_type,
-            visibility_ranges_buffer_binding_type,
-        );
 
         // A 1x1x1 'all 1.0' texture to use as a dummy texture to use in place of optional StandardMaterial textures
         let dummy_white_gpu_image = {
@@ -1113,7 +1107,7 @@ impl FromWorld for MeshPipeline {
         };
 
         MeshPipeline {
-            view_layouts,
+            view_layouts: view_layouts.clone(),
             clustered_forward_buffer_binding_type,
             dummy_white_gpu_image,
             mesh_layouts: MeshLayouts::new(&render_device),
@@ -1141,16 +1135,7 @@ impl MeshPipeline {
     }
 
     pub fn get_view_layout(&self, layout_key: MeshPipelineViewLayoutKey) -> &BindGroupLayout {
-        let index = layout_key.bits() as usize;
-        let layout = &self.view_layouts[index];
-
-        #[cfg(debug_assertions)]
-        if layout.texture_count > MESH_PIPELINE_VIEW_LAYOUT_SAFE_MAX_TEXTURES {
-            // Issue our own warning here because Naga's error message is a bit cryptic in this situation
-            warn_once!("Too many textures in mesh pipeline view layout, this might cause us to hit `wgpu::Limits::max_sampled_textures_per_shader_stage` in some environments.");
-        }
-
-        &layout.bind_group_layout
+        self.view_layouts.get_view_layout(layout_key)
     }
 }
 

crates/bevy_pbr/src/render/mesh_view_bindings.rs

@@ -1,4 +1,4 @@
-use std::{array, num::NonZeroU64};
+use std::{array, num::NonZeroU64, sync::Arc};
 
 use bevy_core_pipeline::{
     core_3d::ViewTransmissionTexture,
@@ -7,10 +7,12 @@ use bevy_core_pipeline::{
         get_lut_bind_group_layout_entries, get_lut_bindings, Tonemapping, TonemappingLuts,
     },
 };
+use bevy_derive::{Deref, DerefMut};
 use bevy_ecs::{
     component::Component,
     entity::Entity,
-    system::{Commands, Query, Res},
+    system::{Commands, Query, Res, Resource},
+    world::{FromWorld, World},
 };
 use bevy_math::Vec4;
 use bevy_render::{
@@ -19,13 +21,19 @@ use bevy_render::{
     render_resource::{binding_types::*, *},
     renderer::RenderDevice,
     texture::{BevyDefault, FallbackImage, FallbackImageMsaa, FallbackImageZero, GpuImage},
-    view::{Msaa, RenderVisibilityRanges, ViewUniform, ViewUniforms},
+    view::{
+        Msaa, RenderVisibilityRanges, ViewUniform, ViewUniforms,
+        VISIBILITY_RANGES_STORAGE_BUFFER_COUNT,
+    },
 };
 
 #[cfg(all(feature = "webgl", target_arch = "wasm32", not(feature = "webgpu")))]
 use bevy_render::render_resource::binding_types::texture_cube;
+use bevy_utils::warn_once;
 use environment_map::EnvironmentMapLight;
 
+#[cfg(debug_assertions)]
+use crate::MESH_PIPELINE_VIEW_LAYOUT_SAFE_MAX_TEXTURES;
 use crate::{
     environment_map::{self, RenderViewEnvironmentMapBindGroupEntries},
     irradiance_volume::{
@@ -35,6 +43,7 @@ use crate::{
     prepass, FogMeta, GlobalLightMeta, GpuFog, GpuLights, GpuPointLights, LightMeta,
     LightProbesBuffer, LightProbesUniform, MeshPipeline, MeshPipelineKey, RenderViewLightProbes,
     ScreenSpaceAmbientOcclusionTextures, ShadowSamplers, ViewClusterBindings, ViewShadowBindings,
+    CLUSTERED_FORWARD_STORAGE_BUFFER_COUNT,
 };
 
 #[derive(Clone)]
@@ -330,6 +339,65 @@ fn layout_entries(
     entries.to_vec()
 }
 
+/// Stores the view layouts for every combination of pipeline keys.
+///
+/// This is wrapped in an [`Arc`] so that it can be efficiently cloned and
+/// placed inside specializable pipeline types.
+#[derive(Resource, Clone, Deref, DerefMut)]
+pub struct MeshPipelineViewLayouts(
+    pub Arc<[MeshPipelineViewLayout; MeshPipelineViewLayoutKey::COUNT]>,
+);
+
+impl FromWorld for MeshPipelineViewLayouts {
+    fn from_world(world: &mut World) -> Self {
+        // Generates all possible view layouts for the mesh pipeline, based on all combinations of
+        // [`MeshPipelineViewLayoutKey`] flags.
+
+        let render_device = world.resource::<RenderDevice>();
+
+        let clustered_forward_buffer_binding_type = render_device
+            .get_supported_read_only_binding_type(CLUSTERED_FORWARD_STORAGE_BUFFER_COUNT);
+        let visibility_ranges_buffer_binding_type = render_device
+            .get_supported_read_only_binding_type(VISIBILITY_RANGES_STORAGE_BUFFER_COUNT);
+
+        Self(Arc::new(array::from_fn(|i| {
+            let key = MeshPipelineViewLayoutKey::from_bits_truncate(i as u32);
+            let entries = layout_entries(
+                clustered_forward_buffer_binding_type,
+                visibility_ranges_buffer_binding_type,
+                key,
+                render_device,
+            );
+            let texture_count: usize = entries
+                .iter()
+                .filter(|entry| matches!(entry.ty, BindingType::Texture { .. }))
+                .count();
+
+            MeshPipelineViewLayout {
+                bind_group_layout: render_device
+                    .create_bind_group_layout(key.label().as_str(), &entries),
+                #[cfg(debug_assertions)]
+                texture_count,
+            }
+        })))
+    }
+}
+
+impl MeshPipelineViewLayouts {
+    pub fn get_view_layout(&self, layout_key: MeshPipelineViewLayoutKey) -> &BindGroupLayout {
+        let index = layout_key.bits() as usize;
+        let layout = &self[index];
+
+        #[cfg(debug_assertions)]
+        if layout.texture_count > MESH_PIPELINE_VIEW_LAYOUT_SAFE_MAX_TEXTURES {
+            // Issue our own warning here because Naga's error message is a bit cryptic in this situation
+            warn_once!("Too many textures in mesh pipeline view layout, this might cause us to hit `wgpu::Limits::max_sampled_textures_per_shader_stage` in some environments.");
+        }
+
+        &layout.bind_group_layout
+    }
+}
+
 /// Generates all possible view layouts for the mesh pipeline, based on all combinations of
 /// [`MeshPipelineViewLayoutKey`] flags.
 pub fn generate_view_layouts(