Port bevy_core_pipeline to LinearRgba (#12116)

# Objective

- We should move towards a consistent use of the new `bevy_color` crate.
- As discussed in #12089, splitting this work up into small pieces makes
it easier to review.

## Solution

- Port all uses of `LegacyColor` in the `bevy_core_pipeline` to
`LinearRgba`
- `LinearRgba` is the correct type to use for internal rendering types
- Added `LinearRgba::BLACK` and `WHITE` (used during migration)
- Add `LinearRgba::grey` to more easily construct balanced grey colors
(used during migration)
- Add a conversion from `LinearRgba` to `wgpu::Color`. The converse was
not done at this time, as this is typically a user error.

I did not change the field type of the clear color on the cameras: as
this is user-facing, this should be done in concert with the other
configurable fields.

## Migration Guide

`ColorAttachment` now stores a `LinearRgba` color, rather than a Bevy
0.13 `Color`.
`set_blend_constant` now takes a `LinearRgba` argument, rather than a
Bevy 0.13 `Color`.

---------

Co-authored-by: Alice Cecile <alice.i.cecil@gmail.com>

crates/bevy_color/Cargo.toml

@@ -15,6 +15,7 @@ bevy_reflect = { path = "../bevy_reflect", version = "0.14.0-dev", features = [
 ] }
 serde = "1.0"
 thiserror = "1.0"
+wgpu = { version = "0.19.1", default-features = false }
 
 [lints]
 workspace = true

crates/bevy_color/src/linear_rgba.rs

@@ -23,6 +23,30 @@ pub struct LinearRgba {
 impl StandardColor for LinearRgba {}
 
 impl LinearRgba {
+    /// A fully black color with full alpha.
+    pub const BLACK: Self = Self {
+        red: 0.0,
+        green: 0.0,
+        blue: 0.0,
+        alpha: 1.0,
+    };
+
+    /// A fully white color with full alpha.
+    pub const WHITE: Self = Self {
+        red: 1.0,
+        green: 1.0,
+        blue: 1.0,
+        alpha: 1.0,
+    };
+
+    /// A fully transparent color.
+    pub const NONE: Self = Self {
+        red: 0.0,
+        green: 0.0,
+        blue: 0.0,
+        alpha: 0.0,
+    };
+
     /// Construct a new [`LinearRgba`] color from components.
     pub const fn new(red: f32, green: f32, blue: f32, alpha: f32) -> Self {
         Self {
@@ -49,6 +73,18 @@ impl LinearRgba {
         }
     }
 
+    /// Construct a new [`LinearRgba`] color with the same value for all channels and an alpha of 1.0.
+    ///
+    /// A value of 0.0 is black, and a value of 1.0 is white.
+    pub const fn gray(value: f32) -> Self {
+        Self {
+            red: value,
+            green: value,
+            blue: value,
+            alpha: 1.0,
+        }
+    }
+
     /// Return a copy of this color with the red channel set to the given value.
     pub const fn with_red(self, red: f32) -> Self {
         Self { red, ..self }
@@ -81,12 +117,7 @@ impl LinearRgba {
 impl Default for LinearRgba {
     /// Construct a new [`LinearRgba`] color with the default values (white with full alpha).
     fn default() -> Self {
-        Self {
-            red: 1.,
-            green: 1.,
-            blue: 1.,
-            alpha: 1.,
-        }
+        Self::WHITE
     }
 }
 
@@ -205,6 +236,17 @@ impl From<Hsla> for LinearRgba {
     }
 }
 
+impl From<LinearRgba> for wgpu::Color {
+    fn from(color: LinearRgba) -> Self {
+        wgpu::Color {
+            r: color.red as f64,
+            g: color.green as f64,
+            b: color.blue as f64,
+            a: color.alpha as f64,
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

crates/bevy_core_pipeline/Cargo.toml

@@ -24,6 +24,7 @@ tonemapping_luts = ["bevy_render/ktx2", "bevy_render/zstd"]
 bevy_app = { path = "../bevy_app", version = "0.14.0-dev" }
 bevy_asset = { path = "../bevy_asset", version = "0.14.0-dev" }
 bevy_core = { path = "../bevy_core", version = "0.14.0-dev" }
+bevy_color = { path = "../bevy_color", version = "0.14.0-dev" }
 bevy_derive = { path = "../bevy_derive", version = "0.14.0-dev" }
 bevy_ecs = { path = "../bevy_ecs", version = "0.14.0-dev" }
 bevy_log = { path = "../bevy_log", version = "0.14.0-dev" }

crates/bevy_core_pipeline/src/bloom/mod.rs

@@ -2,6 +2,7 @@ mod downsampling_pipeline;
 mod settings;
 mod upsampling_pipeline;
 
+use bevy_color::LinearRgba;
 pub use settings::{BloomCompositeMode, BloomPrefilterSettings, BloomSettings};
 
 use crate::{
@@ -17,7 +18,6 @@ use bevy_render::{
     extract_component::{
         ComponentUniforms, DynamicUniformIndex, ExtractComponentPlugin, UniformComponentPlugin,
     },
-    prelude::LegacyColor,
     render_graph::{NodeRunError, RenderGraphApp, RenderGraphContext, ViewNode, ViewNodeRunner},
     render_resource::*,
     renderer::{RenderContext, RenderDevice},
@@ -244,7 +244,7 @@ impl ViewNode for BloomNode {
                 mip as f32,
                 (bloom_texture.mip_count - 1) as f32,
             );
-            upsampling_pass.set_blend_constant(LegacyColor::rgb_linear(blend, blend, blend));
+            upsampling_pass.set_blend_constant(LinearRgba::gray(blend));
             upsampling_pass.draw(0..3, 0..1);
         }
 
@@ -271,7 +271,7 @@ impl ViewNode for BloomNode {
             }
             let blend =
                 compute_blend_factor(bloom_settings, 0.0, (bloom_texture.mip_count - 1) as f32);
-            upsampling_final_pass.set_blend_constant(LegacyColor::rgb_linear(blend, blend, blend));
+            upsampling_final_pass.set_blend_constant(LinearRgba::gray(blend));
             upsampling_final_pass.draw(0..3, 0..1);
         }
 

crates/bevy_core_pipeline/src/core_3d/mod.rs

@@ -41,6 +41,7 @@ pub const CORE_3D_DEPTH_FORMAT: TextureFormat = TextureFormat::Depth32Float;
 use std::ops::Range;
 
 use bevy_asset::AssetId;
+use bevy_color::LinearRgba;
 pub use camera_3d::*;
 pub use main_opaque_pass_3d_node::*;
 pub use main_transparent_pass_3d_node::*;
@@ -49,7 +50,6 @@ use bevy_app::{App, Plugin, PostUpdate};
 use bevy_ecs::prelude::*;
 use bevy_render::{
     camera::{Camera, ExtractedCamera},
-    color::LegacyColor,
     extract_component::ExtractComponentPlugin,
     mesh::Mesh,
     prelude::Msaa,
@@ -836,18 +836,18 @@ pub fn prepare_prepass_textures(
 
         commands.entity(entity).insert(ViewPrepassTextures {
             depth: cached_depth_texture
-                .map(|t| ColorAttachment::new(t, None, Some(LegacyColor::BLACK))),
+                .map(|t| ColorAttachment::new(t, None, Some(LinearRgba::BLACK))),
             normal: cached_normals_texture
-                .map(|t| ColorAttachment::new(t, None, Some(LegacyColor::BLACK))),
+                .map(|t| ColorAttachment::new(t, None, Some(LinearRgba::BLACK))),
             // Red and Green channels are X and Y components of the motion vectors
             // Blue channel doesn't matter, but set to 0.0 for possible faster clear
             // https://gpuopen.com/performance/#clears
             motion_vectors: cached_motion_vectors_texture
-                .map(|t| ColorAttachment::new(t, None, Some(LegacyColor::BLACK))),
+                .map(|t| ColorAttachment::new(t, None, Some(LinearRgba::BLACK))),
             deferred: cached_deferred_texture
-                .map(|t| ColorAttachment::new(t, None, Some(LegacyColor::BLACK))),
+                .map(|t| ColorAttachment::new(t, None, Some(LinearRgba::BLACK))),
             deferred_lighting_pass_id: cached_deferred_lighting_pass_id_texture
-                .map(|t| ColorAttachment::new(t, None, Some(LegacyColor::BLACK))),
+                .map(|t| ColorAttachment::new(t, None, Some(LinearRgba::BLACK))),
             size,
         });
     }

crates/bevy_core_pipeline/src/msaa_writeback.rs

@@ -4,10 +4,10 @@ use crate::{
     core_3d::graph::{Core3d, Node3d},
 };
 use bevy_app::{App, Plugin};
+use bevy_color::LinearRgba;
 use bevy_ecs::prelude::*;
 use bevy_render::{
     camera::ExtractedCamera,
-    color::LegacyColor,
     render_graph::{Node, NodeRunError, RenderGraphApp, RenderGraphContext},
     renderer::RenderContext,
     view::{Msaa, ViewTarget},
@@ -92,7 +92,7 @@ impl Node for MsaaWritebackNode {
                     view: target.sampled_main_texture_view().unwrap(),
                     resolve_target: Some(post_process.destination),
                     ops: Operations {
-                        load: LoadOp::Clear(LegacyColor::BLACK.into()),
+                        load: LoadOp::Clear(LinearRgba::BLACK.into()),
                         store: StoreOp::Store,
                     },
                 })],

crates/bevy_render/src/render_phase/draw_state.rs

@@ -1,12 +1,12 @@
 use crate::{
     camera::Viewport,
-    prelude::LegacyColor,
     render_resource::{
         BindGroup, BindGroupId, Buffer, BufferId, BufferSlice, RenderPipeline, RenderPipelineId,
         ShaderStages,
     },
     renderer::RenderDevice,
 };
+use bevy_color::LinearRgba;
 use bevy_utils::{default, detailed_trace};
 use std::ops::Range;
 use wgpu::{IndexFormat, RenderPass};
@@ -598,7 +598,7 @@ impl<'a> TrackedRenderPass<'a> {
     /// Sets the blend color as used by some of the blending modes.
     ///
     /// Subsequent blending tests will test against this value.
-    pub fn set_blend_constant(&mut self, color: LegacyColor) {
+    pub fn set_blend_constant(&mut self, color: LinearRgba) {
         detailed_trace!("set blend constant: {:?}", color);
         self.pass.set_blend_constant(wgpu::Color::from(color));
     }

crates/bevy_render/src/texture/texture_attachment.rs

@@ -1,5 +1,6 @@
 use super::CachedTexture;
-use crate::{prelude::LegacyColor, render_resource::TextureView};
+use crate::render_resource::TextureView;
+use bevy_color::LinearRgba;
 use std::sync::{
     atomic::{AtomicBool, Ordering},
     Arc,
@@ -13,7 +14,7 @@ use wgpu::{
 pub struct ColorAttachment {
     pub texture: CachedTexture,
     pub resolve_target: Option<CachedTexture>,
-    clear_color: Option<LegacyColor>,
+    clear_color: Option<LinearRgba>,
     is_first_call: Arc<AtomicBool>,
 }
 
@@ -21,7 +22,7 @@ impl ColorAttachment {
     pub fn new(
         texture: CachedTexture,
         resolve_target: Option<CachedTexture>,
-        clear_color: Option<LegacyColor>,
+        clear_color: Option<LinearRgba>,
     ) -> Self {
         Self {
             texture,

crates/bevy_render/src/view/mod.rs

@@ -551,9 +551,11 @@ pub fn prepare_view_targets(
                         (a, b, sampled, main_texture)
                     });
 
+                let converted_clear_color = clear_color.map(|color| color.into());
+
                 let main_textures = MainTargetTextures {
-                    a: ColorAttachment::new(a.clone(), sampled.clone(), clear_color),
-                    b: ColorAttachment::new(b.clone(), sampled.clone(), clear_color),
+                    a: ColorAttachment::new(a.clone(), sampled.clone(), converted_clear_color),
+                    b: ColorAttachment::new(b.clone(), sampled.clone(), converted_clear_color),
                     main_texture: main_texture.clone(),
                 };