separate tonemapping and upscaling passes (bevyengine#3425)

Attempt to make features like bloom bevyengine#2876 easier to implement.

**This PR:**
- Moves the tonemapping from `pbr.wgsl` into a separate pass
- also add a separate upscaling pass after the tonemapping which writes to the swap chain (enables resolution-independant rendering and post-processing after tonemapping)
- adds a `hdr` bool to the camera which controls whether the pbr and sprite shaders render into a `Rgba16Float` texture

**Open questions:**
- ~should the 2d graph work the same as the 3d one?~ it is the same now
- ~The current solution is a bit inflexible because while you can add a post processing pass that writes to e.g. the `hdr_texture`, you can't write to a separate `user_postprocess_texture` while reading the `hdr_texture` and tell the tone mapping pass to read from the `user_postprocess_texture` instead. If the tonemapping and upscaling render graph nodes were to take in a `TextureView` instead of the view entity this would almost work, but the bind groups for their respective input textures are already created in the `Queue` render stage in the hardcoded order.~ solved by creating bind groups in render node

**New render graph:**

![render_graph](https://user-images.githubusercontent.com/22177966/147767249-57dd4229-cfab-4ec5-9bf3-dc76dccf8e8b.png)
<details>
<summary>Before</summary>

![render_graph_old](https://user-images.githubusercontent.com/22177966/147284579-c895fdbd-4028-41cf-914c-e1ffef60e44e.png)
</details>

Co-authored-by: Carter Anderson <[email protected]>

crates/bevy_core_pipeline/Cargo.toml

@@ -19,6 +19,7 @@ webgl = []
 [dependencies]
 # bevy
 bevy_app = { path = "../bevy_app", version = "0.9.0-dev" }
+bevy_asset = { path = "../bevy_asset", version = "0.9.0-dev" }
 bevy_derive = { path = "../bevy_derive", version = "0.9.0-dev" }
 bevy_ecs = { path = "../bevy_ecs", version = "0.9.0-dev" }
 bevy_reflect = { path = "../bevy_reflect", version = "0.9.0-dev" }
@@ -27,4 +28,5 @@ bevy_transform = { path = "../bevy_transform", version = "0.9.0-dev" }
 bevy_utils = { path = "../bevy_utils", version = "0.9.0-dev" }
 
 serde = { version = "1", features = ["derive"] }
+bitflags = "1.2"
 radsort = "0.1"

crates/bevy_core_pipeline/src/core_2d/camera_2d.rs

@@ -1,4 +1,4 @@
-use crate::clear_color::ClearColorConfig;
+use crate::{clear_color::ClearColorConfig, tonemapping::Tonemapping};
 use bevy_ecs::{prelude::*, query::QueryItem};
 use bevy_reflect::Reflect;
 use bevy_render::{
@@ -34,6 +34,7 @@ pub struct Camera2dBundle {
     pub transform: Transform,
     pub global_transform: GlobalTransform,
     pub camera_2d: Camera2d,
+    pub tonemapping: Tonemapping,
 }
 
 impl Default for Camera2dBundle {
@@ -74,6 +75,7 @@ impl Camera2dBundle {
             global_transform: Default::default(),
             camera: Camera::default(),
             camera_2d: Camera2d::default(),
+            tonemapping: Tonemapping { is_enabled: false },
         }
     }
 }

crates/bevy_core_pipeline/src/core_2d/mod.rs

@@ -8,6 +8,8 @@ pub mod graph {
     }
     pub mod node {
         pub const MAIN_PASS: &str = "main_pass";
+        pub const TONEMAPPING: &str = "tonemapping";
+        pub const UPSCALING: &str = "upscaling";
     }
 }
 
@@ -30,6 +32,8 @@ use bevy_render::{
 use bevy_utils::FloatOrd;
 use std::ops::Range;
 
+use crate::{tonemapping::TonemappingNode, upscaling::UpscalingNode};
+
 pub struct Core2dPlugin;
 
 impl Plugin for Core2dPlugin {
@@ -52,10 +56,14 @@ impl Plugin for Core2dPlugin {
             );
 
         let pass_node_2d = MainPass2dNode::new(&mut render_app.world);
+        let tonemapping = TonemappingNode::new(&mut render_app.world);
+        let upscaling = UpscalingNode::new(&mut render_app.world);
         let mut graph = render_app.world.resource_mut::<RenderGraph>();
 
         let mut draw_2d_graph = RenderGraph::default();
         draw_2d_graph.add_node(graph::node::MAIN_PASS, pass_node_2d);
+        draw_2d_graph.add_node(graph::node::TONEMAPPING, tonemapping);
+        draw_2d_graph.add_node(graph::node::UPSCALING, upscaling);
         let input_node_id = draw_2d_graph.set_input(vec![SlotInfo::new(
             graph::input::VIEW_ENTITY,
             SlotType::Entity,
@@ -68,6 +76,28 @@ impl Plugin for Core2dPlugin {
                 MainPass2dNode::IN_VIEW,
             )
             .unwrap();
+        draw_2d_graph
+            .add_slot_edge(
+                input_node_id,
+                graph::input::VIEW_ENTITY,
+                graph::node::TONEMAPPING,
+                TonemappingNode::IN_VIEW,
+            )
+            .unwrap();
+        draw_2d_graph
+            .add_slot_edge(
+                input_node_id,
+                graph::input::VIEW_ENTITY,
+                graph::node::UPSCALING,
+                UpscalingNode::IN_VIEW,
+            )
+            .unwrap();
+        draw_2d_graph
+            .add_node_edge(graph::node::MAIN_PASS, graph::node::TONEMAPPING)
+            .unwrap();
+        draw_2d_graph
+            .add_node_edge(graph::node::TONEMAPPING, graph::node::UPSCALING)
+            .unwrap();
         graph.add_sub_graph(graph::NAME, draw_2d_graph);
     }
 }

crates/bevy_core_pipeline/src/core_3d/camera_3d.rs

@@ -1,4 +1,4 @@
-use crate::clear_color::ClearColorConfig;
+use crate::{clear_color::ClearColorConfig, tonemapping::Tonemapping};
 use bevy_ecs::{prelude::*, query::QueryItem};
 use bevy_reflect::{Reflect, ReflectDeserialize, ReflectSerialize};
 use bevy_render::{
@@ -66,13 +66,15 @@ pub struct Camera3dBundle {
     pub transform: Transform,
     pub global_transform: GlobalTransform,
     pub camera_3d: Camera3d,
+    pub tonemapping: Tonemapping,
 }
 
 // NOTE: ideally Perspective and Orthographic defaults can share the same impl, but sadly it breaks rust's type inference
 impl Default for Camera3dBundle {
     fn default() -> Self {
         Self {
             camera_render_graph: CameraRenderGraph::new(crate::core_3d::graph::NAME),
+            tonemapping: Tonemapping { is_enabled: true },
             camera: Default::default(),
             projection: Default::default(),
             visible_entities: Default::default(),

crates/bevy_core_pipeline/src/core_3d/mod.rs

@@ -8,6 +8,8 @@ pub mod graph {
     }
     pub mod node {
         pub const MAIN_PASS: &str = "main_pass";
+        pub const TONEMAPPING: &str = "tonemapping";
+        pub const UPSCALING: &str = "upscaling";
     }
 }
 
@@ -38,6 +40,8 @@ use bevy_render::{
 };
 use bevy_utils::{FloatOrd, HashMap};
 
+use crate::{tonemapping::TonemappingNode, upscaling::UpscalingNode};
+
 pub struct Core3dPlugin;
 
 impl Plugin for Core3dPlugin {
@@ -62,10 +66,14 @@ impl Plugin for Core3dPlugin {
             .add_system_to_stage(RenderStage::PhaseSort, sort_phase_system::<Transparent3d>);
 
         let pass_node_3d = MainPass3dNode::new(&mut render_app.world);
+        let tonemapping = TonemappingNode::new(&mut render_app.world);
+        let upscaling = UpscalingNode::new(&mut render_app.world);
         let mut graph = render_app.world.resource_mut::<RenderGraph>();
 
         let mut draw_3d_graph = RenderGraph::default();
         draw_3d_graph.add_node(graph::node::MAIN_PASS, pass_node_3d);
+        draw_3d_graph.add_node(graph::node::TONEMAPPING, tonemapping);
+        draw_3d_graph.add_node(graph::node::UPSCALING, upscaling);
         let input_node_id = draw_3d_graph.set_input(vec![SlotInfo::new(
             graph::input::VIEW_ENTITY,
             SlotType::Entity,
@@ -78,6 +86,28 @@ impl Plugin for Core3dPlugin {
                 MainPass3dNode::IN_VIEW,
             )
             .unwrap();
+        draw_3d_graph
+            .add_slot_edge(
+                input_node_id,
+                graph::input::VIEW_ENTITY,
+                graph::node::TONEMAPPING,
+                TonemappingNode::IN_VIEW,
+            )
+            .unwrap();
+        draw_3d_graph
+            .add_slot_edge(
+                input_node_id,
+                graph::input::VIEW_ENTITY,
+                graph::node::UPSCALING,
+                UpscalingNode::IN_VIEW,
+            )
+            .unwrap();
+        draw_3d_graph
+            .add_node_edge(graph::node::MAIN_PASS, graph::node::TONEMAPPING)
+            .unwrap();
+        draw_3d_graph
+            .add_node_edge(graph::node::TONEMAPPING, graph::node::UPSCALING)
+            .unwrap();
         graph.add_sub_graph(graph::NAME, draw_3d_graph);
     }
 }

crates/bevy_core_pipeline/src/fullscreen_vertex_shader/fullscreen.wgsl

@@ -0,0 +1,16 @@
+#define_import_path bevy_core_pipeline::fullscreen_vertex_shader
+
+struct FullscreenVertexOutput {
+    @builtin(position)
+    position: vec4<f32>,
+    @location(0)
+    uv: vec2<f32>,
+};
+
+@vertex
+fn fullscreen_vertex_shader(@builtin(vertex_index) vertex_index: u32) -> FullscreenVertexOutput {
+    let uv = vec2<f32>(f32(vertex_index >> 1u), f32(vertex_index & 1u)) * 2.0;
+    let clip_position = vec4<f32>(uv * vec2<f32>(2.0, -2.0) + vec2<f32>(-1.0, 1.0), 0.0, 1.0);
+
+    return FullscreenVertexOutput(clip_position, uv);
+}

crates/bevy_core_pipeline/src/fullscreen_vertex_shader/mod.rs

@@ -0,0 +1,26 @@
+use bevy_asset::HandleUntyped;
+use bevy_reflect::TypeUuid;
+use bevy_render::{prelude::Shader, render_resource::VertexState};
+
+pub const FULLSCREEN_SHADER_HANDLE: HandleUntyped =
+    HandleUntyped::weak_from_u64(Shader::TYPE_UUID, 7837534426033940724);
+
+/// uses the [`FULLSCREEN_SHADER_HANDLE`] to output a
+/// ```wgsl
+/// struct FullscreenVertexOutput {
+///     [[builtin(position)]]
+///     position: vec4<f32>;
+///     [[location(0)]]
+///     uv: vec2<f32>;
+/// };
+/// ```
+/// from the vertex shader.
+/// The draw call should render one triangle: `render_pass.draw(0..3, 0..1);`
+pub fn fullscreen_shader_vertex_state() -> VertexState {
+    VertexState {
+        shader: FULLSCREEN_SHADER_HANDLE.typed(),
+        shader_defs: Vec::new(),
+        entry_point: "fullscreen_vertex_shader".into(),
+        buffers: Vec::new(),
+    }
+}

crates/bevy_core_pipeline/src/lib.rs

@@ -1,6 +1,9 @@
 pub mod clear_color;
 pub mod core_2d;
 pub mod core_3d;
+pub mod fullscreen_vertex_shader;
+pub mod tonemapping;
+pub mod upscaling;
 
 pub mod prelude {
     #[doc(hidden)]
@@ -15,19 +18,32 @@ use crate::{
     clear_color::{ClearColor, ClearColorConfig},
     core_2d::Core2dPlugin,
     core_3d::Core3dPlugin,
+    fullscreen_vertex_shader::FULLSCREEN_SHADER_HANDLE,
+    tonemapping::TonemappingPlugin,
+    upscaling::UpscalingPlugin,
 };
 use bevy_app::{App, Plugin};
-use bevy_render::extract_resource::ExtractResourcePlugin;
+use bevy_asset::load_internal_asset;
+use bevy_render::{extract_resource::ExtractResourcePlugin, prelude::Shader};
 
 #[derive(Default)]
 pub struct CorePipelinePlugin;
 
 impl Plugin for CorePipelinePlugin {
     fn build(&self, app: &mut App) {
+        load_internal_asset!(
+            app,
+            FULLSCREEN_SHADER_HANDLE,
+            "fullscreen_vertex_shader/fullscreen.wgsl",
+            Shader::from_wgsl
+        );
+
         app.register_type::<ClearColor>()
             .register_type::<ClearColorConfig>()
             .init_resource::<ClearColor>()
             .add_plugin(ExtractResourcePlugin::<ClearColor>::default())
+            .add_plugin(TonemappingPlugin)
+            .add_plugin(UpscalingPlugin)
             .add_plugin(Core2dPlugin)
             .add_plugin(Core3dPlugin);
     }

crates/bevy_core_pipeline/src/tonemapping/blit.wgsl

@@ -0,0 +1,11 @@
+#import bevy_core_pipeline::fullscreen_vertex_shader
+
+@group(0) @binding(0)
+var texture: texture_2d<f32>;
+@group(0) @binding(1)
+var texture_sampler: sampler;
+
+@fragment
+fn fs_main(in: FullscreenVertexOutput) -> @location(0) vec4<f32> {
+    return textureSample(texture, texture_sampler, in.uv);
+}