fix: Particle Alpha bug (pixijs#11078)

* fix particles shaders to handle alpha and tint correctly. update test

* update test

src/scene/particle-container/shared/shader/particles.vert

@@ -35,5 +35,5 @@ void main(void){
     }
 
     vUV = aUV;
-    vColor = aColor * uColor;
+    vColor = vec4(aColor.rgb * aColor.a, aColor.a) * uColor;
 }

src/scene/particle-container/shared/shader/particles.wgsl

@@ -1,6 +1,7 @@
 
 struct ParticleUniforms {
   uProjectionMatrix:mat3x3<f32>,
+  uColor:vec4<f32>,
   uResolution:vec2<f32>,
   uRoundPixels:f32,
 };
@@ -31,10 +32,12 @@ fn mainVertex(
 
    let position = vec4((uniforms.uProjectionMatrix * vec3(v, 1.0)).xy, 0.0, 1.0);
 
+    let vColor = vec4(aColor.rgb * aColor.a, aColor.a) * uniforms.uColor;
+
   return VSOutput(
    position,
    aUV,
-   aColor,
+   vColor,
   );
 }
 

tests/visual/scenes/particle/particle.scene.ts

@@ -29,6 +29,13 @@ export const scene: TestScene = {
             particle.rotation = i * 0.01;
 
             particleContainer.addParticle(particle);
+
+            particle.alpha = i / 100;
+
+            if (i % 2 === 0)
+            {
+                particle.tint = 'red';
+            }
         }
 
         scene.addChild(particleContainer);