Add differentiated rendering

src/pipelines/brush/brush-pipeline.ts

@@ -75,11 +75,15 @@ export class BrushPipeline {
             format: 'rgba16float',
             blend: {
               color: {
+                operation: 'add',
+                srcFactor: 'zero',
+                dstFactor: 'one',
+              },
+              alpha: {
                 operation: 'max',
                 srcFactor: 'one',
                 dstFactor: 'one',
               },
-              alpha: {},
             },
           },
         ],

src/pipelines/brush/brush.wgsl

@@ -45,5 +45,6 @@ fn fragment(
       discard;
     }
 
-    return vec4(clamp((settings.brushWidth - distance) / settings.brushBlurWidth, 0, 1));
+    let strength = clamp((settings.brushWidth - distance) / settings.brushBlurWidth, 0, 1);
+    return vec4(0, 0, 0, strength);
 }