Experiment with cancer cells

src/pipelines/diffusion/diffuse.wgsl

@@ -3,8 +3,10 @@ struct Settings {
   deltaTime: f32,
   time: f32,
   
-  diffusionRate: f32,
-  decayRate: f32,
+  diffusionRateTrails: f32,
+  decayRateTrails: f32,
+  diffusionRateBrush: f32,
+  decayRateBrush: f32,
 };
 
 @group(0) @binding(0) var<uniform> settings: Settings;
@@ -22,11 +24,17 @@ fn fragment(@location(0) uv: vec2<f32>) -> @location(0) vec4<f32> {
     + textureSample(trailMap, Sampler, uv + vec2<f32>(1, 0) / settings.size)
   ) / 4;
 
-  let mixed = mix(
-    current,
-    neighbours,
-    settings.diffusionRate
-  ) * (1.0 - settings.decayRate);
+  let mixedTrails = mix(
+    current.rgb,
+    neighbours.rgb,
+    settings.diffusionRateTrails
+  ) * (1.0 - settings.decayRateTrails);
 
-  return clamp(mixed, vec4(0), vec4(1));
+  let mixedBrush = mix(
+    current.a,
+    neighbours.a,
+    settings.diffusionRateBrush
+  ) * (1.0 - settings.decayRateBrush);
+
+  return clamp(vec4(mixedTrails, mixedBrush), vec4(0), vec4(1));
 }

src/pipelines/diffusion/diffusion-pipeline.ts

@@ -5,7 +5,7 @@ import shader from './diffuse.wgsl';
 import { DiffusionSettings } from './diffusion-settings';
 
 export class DiffusionPipeline {
-  private static readonly UNIFORM_COUNT = 16;
+  private static readonly UNIFORM_COUNT = 18;
 
   private readonly pipeline: GPURenderPipeline;
   private readonly uniforms: GPUBuffer;
@@ -45,8 +45,10 @@ export class DiffusionPipeline {
     canvasSize,
     deltaTime,
     time,
-    diffusionRate,
-    decayRate,
+    diffusionRateTrails,
+    decayRateTrails,
+    diffusionRateBrush,
+    decayRateBrush,
   }: CommonParameters & DiffusionSettings) {
     this.device.queue.writeBuffer(
       this.uniforms,
@@ -56,8 +58,10 @@ export class DiffusionPipeline {
         canvasSize[1],
         deltaTime,
         time,
-        diffusionRate,
-        decayRate,
+        diffusionRateTrails,
+        decayRateTrails,
+        diffusionRateBrush,
+        decayRateBrush,
       ])
     );
   }

src/pipelines/diffusion/diffusion-settings.ts

@@ -1,4 +1,6 @@
 export interface DiffusionSettings {
-  diffusionRate: number;
-  decayRate: number;
+  diffusionRateTrails: number;
+  decayRateTrails: number;
+  diffusionRateBrush: number;
+  decayRateBrush: number;
 }