ExtractResourcePlugin (#3745)

# Objective

- Add an `ExtractResourcePlugin` for convenience and consistency

## Solution

- Add an `ExtractResourcePlugin` similar to `ExtractComponentPlugin` but for ECS `Resource`s. The system that is executed simply clones the main world resource into a render world resource, if and only if the main world resource was either added or changed since the last execution of the system.
- Add an `ExtractResource` trait with a `fn extract_resource(res: &Self) -> Self` function. This is used by the `ExtractResourcePlugin` to extract the resource
- Add a derive macro for `ExtractResource` on a `Resource` with the `Clone` trait, that simply returns `res.clone()`
- Use `ExtractResourcePlugin` wherever both possible and appropriate

crates/bevy_core_pipeline/src/lib.rs

@@ -24,6 +24,7 @@ use bevy_ecs::prelude::*;
 use bevy_render::{
     camera::{ActiveCamera, Camera2d, Camera3d, ExtractedCamera, RenderTarget},
     color::Color,
+    extract_resource::{ExtractResource, ExtractResourcePlugin},
     render_graph::{EmptyNode, RenderGraph, SlotInfo, SlotType},
     render_phase::{
         batch_phase_system, sort_phase_system, BatchedPhaseItem, CachedRenderPipelinePhaseItem,
@@ -33,7 +34,7 @@ use bevy_render::{
     renderer::RenderDevice,
     texture::TextureCache,
     view::{ExtractedView, Msaa, ViewDepthTexture},
-    RenderApp, RenderStage, RenderWorld,
+    RenderApp, RenderStage,
 };
 use bevy_utils::FloatOrd;
 
@@ -41,7 +42,7 @@ use bevy_utils::FloatOrd;
 ///
 /// This color appears as the "background" color for simple apps, when
 /// there are portions of the screen with nothing rendered.
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, ExtractResource)]
 pub struct ClearColor(pub Color);
 
 impl Default for ClearColor {
@@ -50,7 +51,7 @@ impl Default for ClearColor {
     }
 }
 
-#[derive(Clone, Debug, Default)]
+#[derive(Clone, Debug, Default, ExtractResource)]
 pub struct RenderTargetClearColors {
     colors: HashMap<RenderTarget, Color>,
 }
@@ -113,7 +114,9 @@ pub enum CorePipelineRenderSystems {
 impl Plugin for CorePipelinePlugin {
     fn build(&self, app: &mut App) {
         app.init_resource::<ClearColor>()
-            .init_resource::<RenderTargetClearColors>();
+            .init_resource::<RenderTargetClearColors>()
+            .add_plugin(ExtractResourcePlugin::<ClearColor>::default())
+            .add_plugin(ExtractResourcePlugin::<RenderTargetClearColors>::default());
 
         let render_app = match app.get_sub_app_mut(RenderApp) {
             Ok(render_app) => render_app,
@@ -125,7 +128,6 @@ impl Plugin for CorePipelinePlugin {
             .init_resource::<DrawFunctions<Opaque3d>>()
             .init_resource::<DrawFunctions<AlphaMask3d>>()
             .init_resource::<DrawFunctions<Transparent3d>>()
-            .add_system_to_stage(RenderStage::Extract, extract_clear_color)
             .add_system_to_stage(RenderStage::Extract, extract_core_pipeline_camera_phases)
             .add_system_to_stage(RenderStage::Prepare, prepare_core_views_system)
             .add_system_to_stage(
@@ -347,24 +349,6 @@ impl CachedRenderPipelinePhaseItem for Transparent3d {
     }
 }
 
-pub fn extract_clear_color(
-    clear_color: Res<ClearColor>,
-    clear_colors: Res<RenderTargetClearColors>,
-    mut render_world: ResMut<RenderWorld>,
-) {
-    // If the clear color has changed
-    if clear_color.is_changed() {
-        // Update the clear color resource in the render world
-        render_world.insert_resource(clear_color.clone());
-    }
-
-    // If the clear color has changed
-    if clear_colors.is_changed() {
-        // Update the clear color resource in the render world
-        render_world.insert_resource(clear_colors.clone());
-    }
-}
-
 pub fn extract_core_pipeline_camera_phases(
     mut commands: Commands,
     active_2d: Res<ActiveCamera<Camera2d>>,

crates/bevy_pbr/src/lib.rs

@@ -39,6 +39,7 @@ use bevy_asset::{load_internal_asset, Assets, Handle, HandleUntyped};
 use bevy_ecs::prelude::*;
 use bevy_reflect::TypeUuid;
 use bevy_render::{
+    extract_resource::ExtractResourcePlugin,
     prelude::Color,
     render_graph::RenderGraph,
     render_phase::{sort_phase_system, AddRenderCommand, DrawFunctions},
@@ -76,6 +77,7 @@ impl Plugin for PbrPlugin {
             .init_resource::<GlobalVisiblePointLights>()
             .init_resource::<DirectionalLightShadowMap>()
             .init_resource::<PointLightShadowMap>()
+            .add_plugin(ExtractResourcePlugin::<AmbientLight>::default())
             .add_system_to_stage(
                 CoreStage::PostUpdate,
                 // NOTE: Clusters need to have been added before update_clusters is run so

crates/bevy_pbr/src/light.rs

@@ -9,6 +9,7 @@ use bevy_reflect::prelude::*;
 use bevy_render::{
     camera::{Camera, CameraProjection, OrthographicProjection},
     color::Color,
+    extract_resource::ExtractResource,
     prelude::Image,
     primitives::{Aabb, CubemapFrusta, Frustum, Plane, Sphere},
     render_resource::BufferBindingType,
@@ -170,7 +171,7 @@ impl Default for DirectionalLightShadowMap {
 }
 
 /// An ambient light, which lights the entire scene equally.
-#[derive(Debug)]
+#[derive(Clone, Debug, ExtractResource)]
 pub struct AmbientLight {
     pub color: Color,
     /// A direct scale factor multiplied with `color` before being passed to the shader.

crates/bevy_pbr/src/material.rs

@@ -15,9 +15,9 @@ use bevy_ecs::{
     world::FromWorld,
 };
 use bevy_render::{
+    extract_component::ExtractComponentPlugin,
     mesh::{Mesh, MeshVertexBufferLayout},
     render_asset::{RenderAsset, RenderAssetPlugin, RenderAssets},
-    render_component::ExtractComponentPlugin,
     render_phase::{
         AddRenderCommand, DrawFunctions, EntityRenderCommand, RenderCommandResult, RenderPhase,
         SetItemPipeline, TrackedRenderPass,

crates/bevy_pbr/src/render/light.rs

@@ -45,11 +45,6 @@ pub enum RenderLightSystems {
     QueueShadows,
 }
 
-pub struct ExtractedAmbientLight {
-    color: Color,
-    brightness: f32,
-}
-
 #[derive(Component)]
 pub struct ExtractedPointLight {
     color: Color,
@@ -63,8 +58,6 @@ pub struct ExtractedPointLight {
     shadow_normal_bias: f32,
 }
 
-pub type ExtractedPointLightShadowMap = PointLightShadowMap;
-
 #[derive(Component)]
 pub struct ExtractedDirectionalLight {
     color: Color,
@@ -76,8 +69,6 @@ pub struct ExtractedDirectionalLight {
     shadow_normal_bias: f32,
 }
 
-pub type ExtractedDirectionalLightShadowMap = DirectionalLightShadowMap;
-
 #[derive(Copy, Clone, ShaderType, Default, Debug)]
 pub struct GpuPointLight {
     // The lower-right 2x2 values of the projection matrix 22 23 32 33
@@ -408,7 +399,6 @@ pub fn extract_clusters(mut commands: Commands, views: Query<(Entity, &Clusters)
 #[allow(clippy::too_many_arguments)]
 pub fn extract_lights(
     mut commands: Commands,
-    ambient_light: Res<AmbientLight>,
     point_light_shadow_map: Res<PointLightShadowMap>,
     directional_light_shadow_map: Res<DirectionalLightShadowMap>,
     global_point_lights: Res<GlobalVisiblePointLights>,
@@ -422,14 +412,14 @@ pub fn extract_lights(
     )>,
     mut previous_point_lights_len: Local<usize>,
 ) {
-    commands.insert_resource(ExtractedAmbientLight {
+    // NOTE: These shadow map resources are extracted here as they are used here too so this avoids
-        color: ambient_light.color,
+    // races between scheduling of ExtractResourceSystems and this system.
-        brightness: ambient_light.brightness,
+    if point_light_shadow_map.is_changed() {
-    });
+        commands.insert_resource(point_light_shadow_map.clone());
-    commands.insert_resource::<ExtractedPointLightShadowMap>(point_light_shadow_map.clone());
+    }
-    commands.insert_resource::<ExtractedDirectionalLightShadowMap>(
+    if directional_light_shadow_map.is_changed() {
-        directional_light_shadow_map.clone(),
+        commands.insert_resource(directional_light_shadow_map.clone());
-    );
+    }
     // This is the point light shadow map texel size for one face of the cube as a distance of 1.0
     // world unit from the light.
     // point_light_texel_size = 2.0 * 1.0 * tan(PI / 4.0) / cube face width in texels
@@ -665,9 +655,9 @@ pub fn prepare_lights(
         (Entity, &ExtractedView, &ExtractedClusterConfig),
         With<RenderPhase<Transparent3d>>,
     >,
-    ambient_light: Res<ExtractedAmbientLight>,
+    ambient_light: Res<AmbientLight>,
-    point_light_shadow_map: Res<ExtractedPointLightShadowMap>,
+    point_light_shadow_map: Res<PointLightShadowMap>,
-    directional_light_shadow_map: Res<ExtractedDirectionalLightShadowMap>,
+    directional_light_shadow_map: Res<DirectionalLightShadowMap>,
     point_lights: Query<(Entity, &ExtractedPointLight)>,
     directional_lights: Query<(Entity, &ExtractedDirectionalLight)>,
 ) {

crates/bevy_pbr/src/render/mesh.rs

@@ -12,12 +12,12 @@ use bevy_ecs::{
 use bevy_math::{Mat4, Vec2};
 use bevy_reflect::TypeUuid;
 use bevy_render::{
+    extract_component::{ComponentUniforms, DynamicUniformIndex, UniformComponentPlugin},
     mesh::{
         skinning::{SkinnedMesh, SkinnedMeshInverseBindposes},
         GpuBufferInfo, Mesh, MeshVertexBufferLayout,
     },
     render_asset::RenderAssets,
-    render_component::{ComponentUniforms, DynamicUniformIndex, UniformComponentPlugin},
     render_phase::{EntityRenderCommand, RenderCommandResult, TrackedRenderPass},
     render_resource::*,
     renderer::{RenderDevice, RenderQueue},

crates/bevy_pbr/src/wireframe.rs

@@ -7,6 +7,7 @@ use bevy_ecs::{prelude::*, reflect::ReflectComponent};
 use bevy_reflect::std_traits::ReflectDefault;
 use bevy_reflect::{Reflect, TypeUuid};
 use bevy_render::{
+    extract_resource::{ExtractResource, ExtractResourcePlugin},
     mesh::{Mesh, MeshVertexBufferLayout},
     render_asset::RenderAssets,
     render_phase::{AddRenderCommand, DrawFunctions, RenderPhase, SetItemPipeline},
@@ -34,7 +35,8 @@ impl Plugin for WireframePlugin {
             Shader::from_wgsl
         );
 
-        app.init_resource::<WireframeConfig>();
+        app.init_resource::<WireframeConfig>()
+            .add_plugin(ExtractResourcePlugin::<WireframeConfig>::default());
 
         if let Ok(render_app) = app.get_sub_app_mut(RenderApp) {
             render_app
@@ -42,18 +44,11 @@ impl Plugin for WireframePlugin {
                 .init_resource::<WireframePipeline>()
                 .init_resource::<SpecializedMeshPipelines<WireframePipeline>>()
                 .add_system_to_stage(RenderStage::Extract, extract_wireframes)
-                .add_system_to_stage(RenderStage::Extract, extract_wireframe_config)
                 .add_system_to_stage(RenderStage::Queue, queue_wireframes);
         }
     }
 }
 
-fn extract_wireframe_config(mut commands: Commands, wireframe_config: Res<WireframeConfig>) {
-    if wireframe_config.is_added() || wireframe_config.is_changed() {
-        commands.insert_resource(wireframe_config.into_inner().clone());
-    }
-}
-
 fn extract_wireframes(mut commands: Commands, query: Query<Entity, With<Wireframe>>) {
     for entity in query.iter() {
         commands.get_or_spawn(entity).insert(Wireframe);
@@ -65,7 +60,7 @@ fn extract_wireframes(mut commands: Commands, query: Query<Entity, With<Wirefram
 #[reflect(Component, Default)]
 pub struct Wireframe;
 
-#[derive(Debug, Clone, Default)]
+#[derive(Debug, Clone, Default, ExtractResource)]
 pub struct WireframeConfig {
     /// Whether to show wireframes for all meshes. If `false`, only meshes with a [Wireframe] component will be rendered.
     pub global: bool,

crates/bevy_render/Cargo.toml

@@ -36,6 +36,7 @@ bevy_ecs = { path = "../bevy_ecs", version = "0.8.0-dev" }
 bevy_encase_derive = { path = "../bevy_encase_derive", version = "0.8.0-dev" }
 bevy_math = { path = "../bevy_math", version = "0.8.0-dev" }
 bevy_reflect = { path = "../bevy_reflect", version = "0.8.0-dev", features = ["bevy"] }
+bevy_render_macros = { path = "macros", version = "0.8.0-dev" }
 bevy_transform = { path = "../bevy_transform", version = "0.8.0-dev" }
 bevy_window = { path = "../bevy_window", version = "0.8.0-dev" }
 bevy_utils = { path = "../bevy_utils", version = "0.8.0-dev" }

crates/bevy_render/macros/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "bevy_render_macros"
+version = "0.8.0-dev"
+edition = "2021"
+description = "Derive implementations for bevy_render"
+homepage = "https://bevyengine.org"
+repository = "https://github.com/bevyengine/bevy"
+license = "MIT OR Apache-2.0"
+keywords = ["bevy"]
+
+[lib]
+proc-macro = true
+
+[dependencies]
+bevy_macro_utils = { path = "../../bevy_macro_utils", version = "0.8.0-dev" }
+
+syn = "1.0"
+proc-macro2 = "1.0"
+quote = "1.0"

crates/bevy_render/macros/src/extract_resource.rs

@@ -0,0 +1,26 @@
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{parse_macro_input, parse_quote, DeriveInput, Path};
+
+pub fn derive_extract_resource(input: TokenStream) -> TokenStream {
+    let mut ast = parse_macro_input!(input as DeriveInput);
+    let bevy_render_path: Path = crate::bevy_render_path();
+
+    ast.generics
+        .make_where_clause()
+        .predicates
+        .push(parse_quote! { Self: Clone });
+
+    let struct_name = &ast.ident;
+    let (impl_generics, type_generics, where_clause) = &ast.generics.split_for_impl();
+
+    TokenStream::from(quote! {
+        impl #impl_generics #bevy_render_path::extract_resource::ExtractResource for #struct_name #type_generics #where_clause {
+            type Source = Self;
+
+            fn extract_resource(source: &Self::Source) -> Self {
+                source.clone()
+            }
+        }
+    })
+}

crates/bevy_render/macros/src/lib.rs

@@ -0,0 +1,16 @@
+mod extract_resource;
+
+use bevy_macro_utils::BevyManifest;
+use proc_macro::TokenStream;
+
+pub(crate) fn bevy_render_path() -> syn::Path {
+    BevyManifest::default()
+        .maybe_get_path("bevy_render")
+        // NOTE: If the derivation is within bevy_render, then we need to return 'crate'
+        .unwrap_or_else(|| BevyManifest::parse_str("crate"))
+}
+
+#[proc_macro_derive(ExtractResource)]
+pub fn derive_extract_resource(input: TokenStream) -> TokenStream {
+    extract_resource::derive_extract_resource(input)
+}

crates/bevy_render/src/extract_resource.rs

@@ -0,0 +1,46 @@
+use std::marker::PhantomData;
+
+use bevy_app::{App, Plugin};
+use bevy_ecs::system::{Commands, Res, Resource};
+pub use bevy_render_macros::ExtractResource;
+
+use crate::{RenderApp, RenderStage};
+
+/// Describes how a resource gets extracted for rendering.
+///
+/// Therefore the resource is transferred from the "main world" into the "render world"
+/// in the [`RenderStage::Extract`](crate::RenderStage::Extract) step.
+pub trait ExtractResource: Resource {
+    type Source: Resource;
+
+    /// Defines how the resource is transferred into the "render world".
+    fn extract_resource(source: &Self::Source) -> Self;
+}
+
+/// This plugin extracts the resources into the "render world".
+///
+/// Therefore it sets up the [`RenderStage::Extract`](crate::RenderStage::Extract) step
+/// for the specified [`Resource`].
+pub struct ExtractResourcePlugin<R: ExtractResource>(PhantomData<R>);
+
+impl<R: ExtractResource> Default for ExtractResourcePlugin<R> {
+    fn default() -> Self {
+        Self(PhantomData)
+    }
+}
+
+impl<R: ExtractResource> Plugin for ExtractResourcePlugin<R> {
+    fn build(&self, app: &mut App) {
+        if let Ok(render_app) = app.get_sub_app_mut(RenderApp) {
+            render_app.add_system_to_stage(RenderStage::Extract, extract_resource::<R>);
+        }
+    }
+}
+
+/// This system extracts the resource of the corresponding [`Resource`] type
+/// by cloning it.
+pub fn extract_resource<R: ExtractResource>(mut commands: Commands, resource: Res<R::Source>) {
+    if resource.is_changed() {
+        commands.insert_resource(R::extract_resource(resource.into_inner()));
+    }
+}

crates/bevy_render/src/lib.rs

@@ -2,10 +2,11 @@ extern crate core;
 
 pub mod camera;
 pub mod color;
+pub mod extract_component;
+pub mod extract_resource;
 pub mod mesh;
 pub mod primitives;
 pub mod render_asset;
-pub mod render_component;
 pub mod render_graph;
 pub mod render_phase;
 pub mod render_resource;

crates/bevy_render/src/view/mod.rs

@@ -10,6 +10,7 @@ pub use window::*;
 
 use crate::{
     camera::ExtractedCamera,
+    extract_resource::{ExtractResource, ExtractResourcePlugin},
     prelude::Image,
     render_asset::RenderAssets,
     render_resource::{DynamicUniformBuffer, ShaderType, Texture, TextureView},
@@ -27,12 +28,14 @@ pub struct ViewPlugin;
 
 impl Plugin for ViewPlugin {
     fn build(&self, app: &mut App) {
-        app.init_resource::<Msaa>().add_plugin(VisibilityPlugin);
+        app.init_resource::<Msaa>()
+            // NOTE: windows.is_changed() handles cases where a window was resized
+            .add_plugin(ExtractResourcePlugin::<Msaa>::default())
+            .add_plugin(VisibilityPlugin);
 
         if let Ok(render_app) = app.get_sub_app_mut(RenderApp) {
             render_app
                 .init_resource::<ViewUniforms>()
-                .add_system_to_stage(RenderStage::Extract, extract_msaa)
                 .add_system_to_stage(RenderStage::Prepare, prepare_view_uniforms)
                 .add_system_to_stage(
                     RenderStage::Prepare,
@@ -42,7 +45,7 @@ impl Plugin for ViewPlugin {
     }
 }
 
-#[derive(Clone)]
+#[derive(Clone, ExtractResource)]
 /// Configuration resource for [Multi-Sample Anti-Aliasing](https://en.wikipedia.org/wiki/Multisample_anti-aliasing).
 ///
 /// # Example
@@ -70,11 +73,6 @@ impl Default for Msaa {
     }
 }
 
-pub fn extract_msaa(mut commands: Commands, msaa: Res<Msaa>) {
-    // NOTE: windows.is_changed() handles cases where a window was resized
-    commands.insert_resource(msaa.clone());
-}
-
 #[derive(Component)]
 pub struct ExtractedView {
     pub projection: Mat4,

crates/bevy_sprite/src/mesh2d/material.rs

@@ -12,9 +12,9 @@ use bevy_ecs::{
 };
 use bevy_log::error;
 use bevy_render::{
+    extract_component::ExtractComponentPlugin,
     mesh::{Mesh, MeshVertexBufferLayout},
     render_asset::{RenderAsset, RenderAssetPlugin, RenderAssets},
-    render_component::ExtractComponentPlugin,
     render_phase::{
         AddRenderCommand, DrawFunctions, EntityRenderCommand, RenderCommandResult, RenderPhase,
         SetItemPipeline, TrackedRenderPass,

crates/bevy_sprite/src/mesh2d/mesh.rs

@@ -7,9 +7,9 @@ use bevy_ecs::{
 use bevy_math::{Mat4, Vec2};
 use bevy_reflect::{Reflect, TypeUuid};
 use bevy_render::{
+    extract_component::{ComponentUniforms, DynamicUniformIndex, UniformComponentPlugin},
     mesh::{GpuBufferInfo, Mesh, MeshVertexBufferLayout},
     render_asset::RenderAssets,
-    render_component::{ComponentUniforms, DynamicUniformIndex, UniformComponentPlugin},
     render_phase::{EntityRenderCommand, RenderCommandResult, TrackedRenderPass},
     render_resource::*,
     renderer::{RenderDevice, RenderQueue},

examples/shader/compute_shader_game_of_life.rs

@@ -7,6 +7,7 @@ use bevy::{
     core_pipeline::node::MAIN_PASS_DEPENDENCIES,
     prelude::*,
     render::{
+        extract_resource::{ExtractResource, ExtractResourcePlugin},
         render_asset::RenderAssets,
         render_graph::{self, RenderGraph},
         render_resource::*,
@@ -66,10 +67,12 @@ pub struct GameOfLifeComputePlugin;
 
 impl Plugin for GameOfLifeComputePlugin {
     fn build(&self, app: &mut App) {
+        // Extract the game of life image resource from the main world into the render world
+        // for operation on by the compute shader and display on the sprite.
+        app.add_plugin(ExtractResourcePlugin::<GameOfLifeImage>::default());
         let render_app = app.sub_app_mut(RenderApp);
         render_app
             .init_resource::<GameOfLifePipeline>()
-            .add_system_to_stage(RenderStage::Extract, extract_game_of_life_image)
             .add_system_to_stage(RenderStage::Queue, queue_bind_group);
 
         let mut render_graph = render_app.world.resource_mut::<RenderGraph>();
@@ -80,15 +83,11 @@ impl Plugin for GameOfLifeComputePlugin {
     }
 }
 
-#[derive(Deref)]
+#[derive(Clone, Deref, ExtractResource)]
 struct GameOfLifeImage(Handle<Image>);
 
 struct GameOfLifeImageBindGroup(BindGroup);
 
-fn extract_game_of_life_image(mut commands: Commands, image: Res<GameOfLifeImage>) {
-    commands.insert_resource(GameOfLifeImage(image.clone()));
-}
-
 fn queue_bind_group(
     mut commands: Commands,
     pipeline: Res<GameOfLifePipeline>,

examples/shader/shader_defs.rs

@@ -8,9 +8,9 @@ use bevy::{
     },
     prelude::*,
     render::{
+        extract_component::{ExtractComponent, ExtractComponentPlugin},
         mesh::MeshVertexBufferLayout,
         render_asset::RenderAssets,
-        render_component::{ExtractComponent, ExtractComponentPlugin},
         render_phase::{AddRenderCommand, DrawFunctions, RenderPhase, SetItemPipeline},
         render_resource::{
             PipelineCache, RenderPipelineDescriptor, SpecializedMeshPipeline,

examples/shader/shader_instancing.rs

@@ -7,9 +7,9 @@ use bevy::{
     pbr::{MeshPipeline, MeshPipelineKey, MeshUniform, SetMeshBindGroup, SetMeshViewBindGroup},
     prelude::*,
     render::{
+        extract_component::{ExtractComponent, ExtractComponentPlugin},
         mesh::{GpuBufferInfo, MeshVertexBufferLayout},
         render_asset::RenderAssets,
-        render_component::{ExtractComponent, ExtractComponentPlugin},
         render_phase::{
             AddRenderCommand, DrawFunctions, EntityRenderCommand, RenderCommandResult, RenderPhase,
             SetItemPipeline, TrackedRenderPass,

tools/publish.sh

@@ -22,6 +22,7 @@ crates=(
     bevy_transform
     bevy_window
     bevy_encase_derive
+    bevy_render/macros
     bevy_render
     bevy_core_pipeline
     bevy_input