Mini Blit refactor (#20118)

# Objective

- Clean up usage of BlitPipeline

## Solution

- add `create_bind_group` method
- adjust some field and variable names for clarity

## Testing

- ran 3d_scene

crates/bevy_core_pipeline/src/blit/mod.rs

@@ -36,7 +36,7 @@ impl Plugin for BlitPlugin {
 
 #[derive(Resource)]
 pub struct BlitPipeline {
-    pub texture_bind_group: BindGroupLayout,
+    pub layout: BindGroupLayout,
     pub sampler: Sampler,
     pub fullscreen_shader: FullscreenShader,
     pub fragment_shader: Handle<Shader>,
@@ -46,7 +46,7 @@ impl FromWorld for BlitPipeline {
     fn from_world(render_world: &mut World) -> Self {
         let render_device = render_world.resource::<RenderDevice>();
 
-        let texture_bind_group = render_device.create_bind_group_layout(
+        let layout = render_device.create_bind_group_layout(
             "blit_bind_group_layout",
             &BindGroupLayoutEntries::sequential(
                 ShaderStages::FRAGMENT,
@@ -60,7 +60,7 @@ impl FromWorld for BlitPipeline {
         let sampler = render_device.create_sampler(&SamplerDescriptor::default());
 
         BlitPipeline {
-            texture_bind_group,
+            layout,
             sampler,
             fullscreen_shader: render_world.resource::<FullscreenShader>().clone(),
             fragment_shader: load_embedded_asset!(render_world, "blit.wgsl"),
@@ -68,6 +68,20 @@ impl FromWorld for BlitPipeline {
     }
 }
 
+impl BlitPipeline {
+    pub fn create_bind_group(
+        &self,
+        render_device: &RenderDevice,
+        src_texture: &TextureView,
+    ) -> BindGroup {
+        render_device.create_bind_group(
+            None,
+            &self.layout,
+            &BindGroupEntries::sequential((src_texture, &self.sampler)),
+        )
+    }
+}
+
 #[derive(PartialEq, Eq, Hash, Clone, Copy)]
 pub struct BlitPipelineKey {
     pub texture_format: TextureFormat,
@@ -81,7 +95,7 @@ impl SpecializedRenderPipeline for BlitPipeline {
     fn specialize(&self, key: Self::Key) -> RenderPipelineDescriptor {
         RenderPipelineDescriptor {
             label: Some("blit pipeline".into()),
-            layout: vec![self.texture_bind_group.clone()],
+            layout: vec![self.layout.clone()],
             vertex: self.fullscreen_shader.to_vertex_state(),
             fragment: Some(FragmentState {
                 shader: self.fragment_shader.clone(),

crates/bevy_core_pipeline/src/msaa_writeback.rs

@@ -98,11 +98,8 @@ impl ViewNode for MsaaWritebackNode {
             occlusion_query_set: None,
         };
 
-        let bind_group = render_context.render_device().create_bind_group(
-            None,
-            &blit_pipeline.texture_bind_group,
-            &BindGroupEntries::sequential((post_process.source, &blit_pipeline.sampler)),
-        );
+        let bind_group =
+            blit_pipeline.create_bind_group(render_context.render_device(), post_process.source);
 
         let mut render_pass = render_context
             .command_encoder()

crates/bevy_core_pipeline/src/upscaling/node.rs

@@ -3,9 +3,7 @@ use bevy_ecs::{prelude::*, query::QueryItem};
 use bevy_render::{
     camera::{CameraOutputMode, ClearColor, ClearColorConfig, ExtractedCamera},
     render_graph::{NodeRunError, RenderGraphContext, ViewNode},
-    render_resource::{
-        BindGroup, BindGroupEntries, PipelineCache, RenderPassDescriptor, TextureViewId,
-    },
+    render_resource::{BindGroup, PipelineCache, RenderPassDescriptor, TextureViewId},
     renderer::RenderContext,
     view::ViewTarget,
 };
@@ -30,9 +28,9 @@ impl ViewNode for UpscalingNode {
         (target, upscaling_target, camera): QueryItem<Self::ViewQuery>,
         world: &World,
     ) -> Result<(), NodeRunError> {
-        let pipeline_cache = world.get_resource::<PipelineCache>().unwrap();
-        let blit_pipeline = world.get_resource::<BlitPipeline>().unwrap();
-        let clear_color_global = world.get_resource::<ClearColor>().unwrap();
+        let pipeline_cache = world.resource::<PipelineCache>();
+        let blit_pipeline = world.resource::<BlitPipeline>();
+        let clear_color_global = world.resource::<ClearColor>();
 
         let clear_color = if let Some(camera) = camera {
             match camera.output_mode {
@@ -48,19 +46,18 @@ impl ViewNode for UpscalingNode {
             ClearColorConfig::None => None,
         };
         let converted_clear_color = clear_color.map(Into::into);
-        let upscaled_texture = target.main_texture_view();
+        // texture to be upscaled to the output texture
+        let main_texture_view = target.main_texture_view();
 
         let mut cached_bind_group = self.cached_texture_bind_group.lock().unwrap();
         let bind_group = match &mut *cached_bind_group {
-            Some((id, bind_group)) if upscaled_texture.id() == *id => bind_group,
+            Some((id, bind_group)) if main_texture_view.id() == *id => bind_group,
             cached_bind_group => {
-                let bind_group = render_context.render_device().create_bind_group(
-                    None,
-                    &blit_pipeline.texture_bind_group,
-                    &BindGroupEntries::sequential((upscaled_texture, &blit_pipeline.sampler)),
-                );
+                let bind_group = blit_pipeline
+                    .create_bind_group(render_context.render_device(), main_texture_view);
 
-                let (_, bind_group) = cached_bind_group.insert((upscaled_texture.id(), bind_group));
+                let (_, bind_group) =
+                    cached_bind_group.insert((main_texture_view.id(), bind_group));
                 bind_group
             }
         };