fix calls to as_rgba_linear (#3200)

# Objective

- After #3192, some places where `as_rgba_linear` was called were doing too many conversions

## Solution

- Fix the conversions

examples/shader/custom_shader_pipelined.rs

@@ -90,7 +90,7 @@ impl RenderAsset for CustomMaterial {
         extracted_asset: Self::ExtractedAsset,
         (render_device, custom_pipeline): &mut SystemParamItem<Self::Param>,
     ) -> Result<Self::PreparedAsset, PrepareAssetError<Self::ExtractedAsset>> {
-        let color: Vec4 = extracted_asset.color.as_rgba_linear().into();
+        let color = Vec4::from_slice(&extracted_asset.color.as_linear_rgba_f32());
         let buffer = render_device.create_buffer_with_data(&BufferInitDescriptor {
             contents: color.as_std140().as_bytes(),
             label: None,

pipelined/bevy_pbr2/src/material.rs

@@ -238,7 +238,7 @@ impl RenderAsset for StandardMaterial {
         };
 
         let value = StandardMaterialUniformData {
-            base_color: material.base_color.as_rgba_linear().into(),
+            base_color: material.base_color.as_linear_rgba_f32().into(),
             emissive: material.emissive.into(),
             roughness: material.perceptual_roughness,
             metallic: material.metallic,

pipelined/bevy_pbr2/src/render/light.rs

@@ -509,7 +509,6 @@ pub fn prepare_lights(
 ) {
     light_meta.view_gpu_lights.clear();
 
-    let ambient_color = ambient_light.color.as_rgba_linear() * ambient_light.brightness;
     // Pre-calculate for PointLights
     let cube_face_projection =
         Mat4::perspective_infinite_reverse_rh(std::f32::consts::FRAC_PI_2, 1.0, 0.1);
@@ -555,7 +554,8 @@ pub fn prepare_lights(
         let mut view_lights = Vec::new();
 
         let mut gpu_lights = GpuLights {
-            ambient_color: ambient_color.into(),
+            ambient_color: Vec4::from_slice(&ambient_light.color.as_linear_rgba_f32())
+                * ambient_light.brightness,
             n_point_lights: point_lights.iter().len() as u32,
             n_directional_lights: directional_lights.iter().len() as u32,
             point_lights: [GpuPointLight::default(); MAX_POINT_LIGHTS],
@@ -622,7 +622,7 @@ pub fn prepare_lights(
                 projection: cube_face_projection,
                 // premultiply color by intensity
                 // we don't use the alpha at all, so no reason to multiply only [0..3]
-                color: (light.color.as_rgba_linear() * light.intensity).into(),
+                color: Vec4::from_slice(&light.color.as_linear_rgba_f32()) * light.intensity,
                 radius: light.radius,
                 position: light.transform.translation,
                 inverse_square_range: 1.0 / (light.range * light.range),
@@ -669,7 +669,7 @@ pub fn prepare_lights(
             gpu_lights.directional_lights[i] = GpuDirectionalLight {
                 // premultiply color by intensity
                 // we don't use the alpha at all, so no reason to multiply only [0..3]
-                color: (light.color.as_rgba_linear() * intensity).into(),
+                color: Vec4::from_slice(&light.color.as_linear_rgba_f32()) * intensity,
                 dir_to_light,
                 // NOTE: * view is correct, it should not be view.inverse() here
                 view_projection: projection * view,

pipelined/bevy_render2/src/color/mod.rs

@@ -633,12 +633,21 @@ impl From<Vec4> for Color {
 
 impl From<Color> for wgpu::Color {
     fn from(color: Color) -> Self {
-        let color = color.as_rgba_linear();
-        wgpu::Color {
-            r: color.r() as f64,
-            g: color.g() as f64,
-            b: color.b() as f64,
-            a: color.a() as f64,
+        if let Color::RgbaLinear {
+            red,
+            green,
+            blue,
+            alpha,
+        } = color.as_rgba_linear()
+        {
+            wgpu::Color {
+                r: red as f64,
+                g: green as f64,
+                b: blue as f64,
+                a: alpha as f64,
+            }
+        } else {
+            unreachable!()
         }
     }
 }