Move the stage that acquires a new texture from the swap chain as late

as possible in the rendering pipeline.

Currently, we retrieve a new texture from the pipeline in
`prepare_windows`, which executes during the `ManageViews` rendering
phase. This is inefficient if we're GPU bound, because `ManageViews`
happens before `queue_material_meshes` and
`batch_and_prepare_binned_render_phase` among other frequently-slow
systems. Retrieving a new texture from the swap chain can block for
considerable time, during which we don't want the CPU to be sitting
idle. Additionally, we don't want the GPU to be sitting idle while the
CPU works on `queue_material_meshes` and so forth.

This commit fixes the issue by moving the acquisition of a new swap
chain texture late in the pipeline, to a new phase `PrepareWindows` that
occurs right before render graph evaluation. Because render graph
evaluation needs to bind the swap chain textures in order to issue
drawing commands, this is the last possible moment where it's safe to do
so.

crates/bevy_core_pipeline/src/auto_exposure/mod.rs

@@ -73,7 +73,9 @@ impl Plugin for AutoExposurePlugin {
             .add_systems(
                 Render,
                 (
-                    prepare_buffers.in_set(RenderSet::Prepare),
+                    prepare_buffers
+                        .in_set(RenderSet::Prepare)
+                        .before(RenderSet::PrepareWindows),
                     queue_view_auto_exposure_pipelines.in_set(RenderSet::Queue),
                 ),
             )

crates/bevy_core_pipeline/src/bloom/mod.rs

@@ -64,8 +64,12 @@ impl Plugin for BloomPlugin {
             .add_systems(
                 Render,
                 (
-                    prepare_downsampling_pipeline.in_set(RenderSet::Prepare),
-                    prepare_upsampling_pipeline.in_set(RenderSet::Prepare),
+                    prepare_downsampling_pipeline
+                        .in_set(RenderSet::Prepare)
+                        .before(RenderSet::PrepareWindows),
+                    prepare_upsampling_pipeline
+                        .in_set(RenderSet::Prepare)
+                        .before(RenderSet::PrepareWindows),
                     prepare_bloom_textures.in_set(RenderSet::PrepareResources),
                     prepare_bloom_bind_groups.in_set(RenderSet::PrepareBindGroups),
                 ),

crates/bevy_core_pipeline/src/dof/mod.rs

@@ -62,7 +62,7 @@ use smallvec::SmallVec;
 use crate::{
     core_3d::{
         graph::{Core3d, Node3d},
-        Camera3d, DEPTH_TEXTURE_SAMPLING_SUPPORTED,
+        prepare_core_3d_depth_textures, Camera3d, DEPTH_TEXTURE_SAMPLING_SUPPORTED,
     },
     fullscreen_vertex_shader::fullscreen_shader_vertex_state,
 };
@@ -226,20 +226,18 @@ impl Plugin for DepthOfFieldPlugin {
             .add_systems(
                 Render,
                 (
-                    configure_depth_of_field_view_targets,
                     prepare_auxiliary_depth_of_field_textures,
+                    prepare_depth_of_field_view_bind_group_layouts,
+                    prepare_depth_of_field_pipelines,
                 )
                     .after(prepare_view_targets)
-                    .in_set(RenderSet::ManageViews),
+                    .in_set(RenderSet::PrepareWindows),
             )
             .add_systems(
                 Render,
-                (
-                    prepare_depth_of_field_view_bind_group_layouts,
-                    prepare_depth_of_field_pipelines,
-                )
-                    .chain()
-                    .in_set(RenderSet::Prepare),
+                configure_depth_of_field_view_targets
+                    .before(prepare_core_3d_depth_textures)
+                    .in_set(RenderSet::PrepareResources),
             )
             .add_systems(
                 Render,

crates/bevy_core_pipeline/src/tonemapping/mod.rs

@@ -15,7 +15,7 @@ use bevy_render::{
     },
     renderer::RenderDevice,
     texture::{FallbackImage, GpuImage},
-    view::{ExtractedView, ViewTarget, ViewUniform},
+    view::{prepare_view_targets, ExtractedView, ViewTarget, ViewUniform},
     Render, RenderApp, RenderSet,
 };
 #[cfg(not(feature = "tonemapping_luts"))]
@@ -117,7 +117,9 @@ impl Plugin for TonemappingPlugin {
             .init_resource::<SpecializedRenderPipelines<TonemappingPipeline>>()
             .add_systems(
                 Render,
-                prepare_view_tonemapping_pipelines.in_set(RenderSet::Prepare),
+                prepare_view_tonemapping_pipelines
+                    .in_set(RenderSet::Prepare)
+                    .after(prepare_view_targets),
             );
     }
 

crates/bevy_core_pipeline/src/upscaling/mod.rs

@@ -27,6 +27,7 @@ impl Plugin for UpscalingPlugin {
                 // See https://github.com/bevyengine/bevy/issues/14770 for more context.
                 prepare_view_upscaling_pipelines
                     .in_set(RenderSet::Prepare)
+                    .after(RenderSet::PrepareWindows)
                     .ambiguous_with_all(),
             );
         }

crates/bevy_pbr/src/deferred/mod.rs

@@ -114,7 +114,7 @@ impl Plugin for DeferredPbrLightingPlugin {
             .init_resource::<SpecializedRenderPipelines<DeferredLightingLayout>>()
             .add_systems(
                 Render,
-                (prepare_deferred_lighting_pipelines.in_set(RenderSet::Prepare),),
+                prepare_deferred_lighting_pipelines.in_set(RenderSet::Prepare),
             )
             .add_render_graph_node::<ViewNodeRunner<DeferredOpaquePass3dPbrLightingNode>>(
                 Core3d,

crates/bevy_pbr/src/meshlet/mod.rs

@@ -287,7 +287,7 @@ impl Plugin for MeshletPlugin {
                     perform_pending_meshlet_mesh_writes.in_set(RenderSet::PrepareAssets),
                     configure_meshlet_views
                         .after(prepare_view_targets)
-                        .in_set(RenderSet::ManageViews),
+                        .in_set(RenderSet::PrepareWindows),
                     prepare_meshlet_per_frame_resources.in_set(RenderSet::PrepareResources),
                     prepare_meshlet_view_bind_groups.in_set(RenderSet::PrepareBindGroups),
                 ),

crates/bevy_pbr/src/render/gpu_preprocess.rs

@@ -153,7 +153,7 @@ impl Plugin for GpuMeshPreprocessPlugin {
             .add_systems(
                 Render,
                 (
-                    prepare_preprocess_pipelines.in_set(RenderSet::Prepare),
+                    prepare_preprocess_pipelines.in_set(RenderSet::Prepare).after(RenderSet::PrepareWindows),
                     prepare_preprocess_bind_groups
                         .run_if(
                             resource_exists::<BatchedInstanceBuffers<MeshUniform, MeshInputUniform>>,

crates/bevy_pbr/src/render/mesh.rs

@@ -37,8 +37,8 @@ use bevy_render::{
     renderer::{RenderAdapter, RenderDevice, RenderQueue},
     texture::DefaultImageSampler,
     view::{
-        prepare_view_targets, NoFrustumCulling, NoIndirectDrawing, RenderVisibilityRanges,
-        ViewTarget, ViewUniformOffset, ViewVisibility, VisibilityRange,
+        NoFrustumCulling, NoIndirectDrawing, RenderVisibilityRanges, ViewTarget, ViewUniformOffset,
+        ViewVisibility, VisibilityRange,
     },
     Extract,
 };
@@ -217,8 +217,7 @@ impl Plugin for MeshRenderPlugin {
                             gpu_preprocessing::write_batched_instance_buffers::<MeshPipeline>
                                 .in_set(RenderSet::PrepareResourcesFlush),
                             gpu_preprocessing::delete_old_work_item_buffers::<MeshPipeline>
-                                .in_set(RenderSet::ManageViews)
-                                .after(prepare_view_targets),
+                                .in_set(RenderSet::PrepareResources),
                             collect_meshes_for_gpu_building
                                 .in_set(RenderSet::PrepareAssets)
                                 .after(allocator::allocate_and_free_meshes)

crates/bevy_pbr/src/ssao/mod.rs

@@ -111,7 +111,9 @@ impl Plugin for ScreenSpaceAmbientOcclusionPlugin {
             .add_systems(
                 Render,
                 (
-                    prepare_ssao_pipelines.in_set(RenderSet::Prepare),
+                    prepare_ssao_pipelines
+                        .in_set(RenderSet::Prepare)
+                        .before(RenderSet::PrepareWindows),
                     prepare_ssao_textures.in_set(RenderSet::PrepareResources),
                     prepare_ssao_bind_groups.in_set(RenderSet::PrepareBindGroups),
                 ),

crates/bevy_pbr/src/volumetric_fog/mod.rs

@@ -247,10 +247,15 @@ impl Plugin for VolumetricFogPlugin {
             .add_systems(
                 Render,
                 (
-                    render::prepare_volumetric_fog_pipelines.in_set(RenderSet::Prepare),
-                    render::prepare_volumetric_fog_uniforms.in_set(RenderSet::Prepare),
+                    render::prepare_volumetric_fog_pipelines
+                        .in_set(RenderSet::Prepare)
+                        .before(RenderSet::PrepareWindows),
+                    render::prepare_volumetric_fog_uniforms
+                        .in_set(RenderSet::Prepare)
+                        .before(RenderSet::PrepareWindows),
                     render::prepare_view_depth_textures_for_volumetric_fog
                         .in_set(RenderSet::Prepare)
+                        .before(RenderSet::PrepareWindows)
                         .before(prepare_core_3d_depth_textures),
                 ),
             );

crates/bevy_render/src/batching/gpu_preprocessing.rs

@@ -16,6 +16,7 @@ use nonmax::NonMaxU32;
 use wgpu::{BindingResource, BufferUsages, DownlevelFlags, Features};
 
 use crate::{
+    camera::ExtractedCamera,
     render_phase::{
         BinnedPhaseItem, BinnedRenderPhaseBatch, BinnedRenderPhaseBatchSets,
         CachedRenderPipelinePhaseItem, PhaseItemBinKey as _, PhaseItemExtraIndex, SortedPhaseItem,
@@ -24,7 +25,7 @@ use crate::{
     },
     render_resource::{BufferVec, GpuArrayBufferable, RawBufferVec, UninitBufferVec},
     renderer::{RenderAdapter, RenderDevice, RenderQueue},
-    view::{ExtractedView, NoIndirectDrawing, ViewTarget},
+    view::{ExtractedView, NoIndirectDrawing},
     Render, RenderApp, RenderSet,
 };
 
@@ -491,14 +492,15 @@ pub fn clear_batched_gpu_instance_buffers<GFBD>(
 /// A system that removes GPU preprocessing work item buffers that correspond to
 /// deleted [`ViewTarget`]s.
 ///
-/// This is a separate system from [`clear_batched_gpu_instance_buffers`]
-/// because [`ViewTarget`]s aren't created until after the extraction phase is
-/// completed.
+/// View targets aren't created until the [`RenderSet::PrepareWindows`] phase,
+/// so we can't issue a query for them directly. Instead, we search for
+/// [`ExtractedView`]s, which the [`crate::view::prepare_view_targets`] system
+/// will attach [`ViewTarget`]s to.
 pub fn delete_old_work_item_buffers<GFBD>(
     mut gpu_batched_instance_buffers: ResMut<
         BatchedInstanceBuffers<GFBD::BufferData, GFBD::BufferInputData>,
     >,
-    view_targets: Query<Entity, With<ViewTarget>>,
+    view_targets: Query<Entity, With<ExtractedView>>,
 ) where
     GFBD: GetFullBatchData,
 {

crates/bevy_render/src/lib.rs

@@ -151,6 +151,12 @@ pub enum RenderSet {
     PrepareResourcesFlush,
     /// A sub-set within [`Prepare`](RenderSet::Prepare) for constructing bind groups, or other data that relies on render resources prepared in [`PrepareResources`](RenderSet::PrepareResources).
     PrepareBindGroups,
+    /// A sub-set within [`Prepare`](RenderSet::Prepare) for acquiring the new
+    /// swap chain buffer.
+    ///
+    /// This may block on the GPU finishing the last frame, so it should be as
+    /// late as possible in order to pipeline the maximum amount of CPU work.
+    PrepareWindows,
     /// Actual rendering happens here.
     /// In most cases, only the render backend should insert resources here.
     Render,
@@ -196,7 +202,12 @@ impl Render {
                 .after(prepare_assets::<RenderMesh>),
         );
         schedule.configure_sets(
-            (PrepareResources, PrepareResourcesFlush, PrepareBindGroups)
+            (
+                PrepareResources,
+                PrepareResourcesFlush,
+                PrepareBindGroups,
+                PrepareWindows,
+            )
                 .chain()
                 .in_set(Prepare),
         );

crates/bevy_render/src/view/mod.rs

@@ -124,14 +124,13 @@ impl Plugin for ViewPlugin {
                         .in_set(RenderSet::ManageViews)
                         .before(create_surfaces),
                     prepare_view_attachments
-                        .in_set(RenderSet::ManageViews)
+                        .in_set(RenderSet::PrepareWindows)
                         .before(prepare_view_targets)
                         .after(prepare_windows),
                     prepare_view_targets
-                        .in_set(RenderSet::ManageViews)
+                        .in_set(RenderSet::PrepareWindows)
                         .after(prepare_windows)
-                        .after(crate::render_asset::prepare_assets::<GpuImage>)
-                        .ambiguous_with(crate::camera::sort_cameras), // doesn't use `sorted_camera_index_for_target`
+                        .after(crate::render_asset::prepare_assets::<GpuImage>),
                     prepare_view_uniforms.in_set(RenderSet::PrepareResources),
                 ),
             );

crates/bevy_render/src/view/window/mod.rs

@@ -42,7 +42,7 @@ impl Plugin for WindowRenderPlugin {
                         .run_if(need_surface_configuration)
                         .before(prepare_windows),
                 )
-                .add_systems(Render, prepare_windows.in_set(RenderSet::ManageViews));
+                .add_systems(Render, prepare_windows.in_set(RenderSet::PrepareWindows));
         }
     }
 

crates/bevy_render/src/view/window/screenshot.rs

@@ -435,7 +435,7 @@ impl Plugin for ScreenshotPlugin {
                     prepare_screenshots
                         .after(prepare_view_attachments)
                         .before(prepare_view_targets)
-                        .in_set(RenderSet::ManageViews),
+                        .in_set(RenderSet::PrepareWindows),
                 );
         }
     }