wasm: Page shows behind skybox when skybox brightness is low

[rparrett]

Bevy version

0.13.1, main

Relevant system information

AdapterInfo { name: "ANGLE (Apple, ANGLE Metal Renderer: Apple M1 Max, Unspecified Version)", vendor: 4203, device: 0, device_type: IntegratedGpu, driver: "", driver_info: "", backend: Gl }

What you did

• With wasm-server-runner
• Change brightness in examples/3d/skybox.rs to 100..
• cargo run --example skybox --target=wasm32-unknown-unknown
• Using browser dev tools, add the following style to body:

  background: repeating-linear-gradient(-45deg, rgb(255, 200, 200), rgb(255, 200, 200) 10px, white 10px, white 20px);

What went wrong

Page background can be seen through the skybox.

Additional information

The following patch seems to fix the problem, but I'm not sure if it's proper.

diff --git a/crates/bevy_core_pipeline/src/skybox/skybox.wgsl b/crates/bevy_core_pipeline/src/skybox/skybox.wgsl
index 593b440ee..37a66cfba 100644
--- a/crates/bevy_core_pipeline/src/skybox/skybox.wgsl
+++ b/crates/bevy_core_pipeline/src/skybox/skybox.wgsl
@@ -72,5 +72,5 @@ fn skybox_fragment(in: VertexOutput) -> @location(0) vec4<f32> {
     let ray_direction = coords_to_ray_direction(in.position.xy, view.viewport);
 
     // Cube maps are left-handed so we negate the z coordinate.
-    return textureSample(skybox, skybox_sampler, ray_direction * vec3(1.0, 1.0, -1.0)) * uniforms.brightness;
+    return vec4<f32>(textureSample(skybox, skybox_sampler, ray_direction * vec3(1.0, 1.0, -1.0)).rgb * uniforms.brightness, 1.0);
 }

[SolarLiner]

The bug is in how the brightness is wrongly applied to the alpha channel, so the fix is the correct one; however your fix also makes it impossible to do transparent backgrouns when that is desired, because the alpha channel is now hardcoded to 1.

The following patch resolves that issue (not tested):

diff --git a/crates/bevy_core_pipeline/src/skybox/skybox.wgsl b/crates/bevy_core_pipeline/src/skybox/skybox.wgsl
index 593b440ee..37a66cfba 100644
--- a/crates/bevy_core_pipeline/src/skybox/skybox.wgsl
+++ b/crates/bevy_core_pipeline/src/skybox/skybox.wgsl
@@ -72,5 +72,5 @@ fn skybox_fragment(in: VertexOutput) -> @location(0) vec4<f32> {
     let ray_direction = coords_to_ray_direction(in.position.xy, view.viewport);
 
     // Cube maps are left-handed so we negate the z coordinate.
-    return textureSample(skybox, skybox_sampler, ray_direction * vec3(1.0, 1.0, -1.0)) * uniforms.brightness;
+    let out = textureSample(skybox, skybox_sampler, ray_direction * vec3(1.0, 1.0, -1.0));
+    out.rgb *= uniforms.brightness;
+    return out;
 }