Block pheromone diffusion through solid materials

Checks each blur neighbor's material behavior before including it in
the average. Solid and non-gas cells are excluded so pheromones don't
bleed through walls, sand, or rock.

src/Renderer.ts

@@ -187,6 +187,8 @@ export default class Renderer {
         this.renderer.setRenderTarget(this.resources.worldBlurredRenderTarget);
         scenes.worldBlur.material.uniforms.tWorld.value =
             this.resources.sandPhysicsRenderTarget.texture;
+        scenes.worldBlur.material.uniforms.uMaterialProps.value =
+            this.materialPropsTexture;
         this.renderer.render(scenes.worldBlur, scenes.worldBlur.camera);
 
         this.renderer.setRenderTarget(this.resources.antsPresenceRenderTarget);

src/scenes/WorldBlurScene.ts

@@ -17,6 +17,7 @@ export default class WorldBlurScene extends AbstractScene {
         const material = new THREE.RawShaderMaterial({
             uniforms: {
                 tWorld: { value: null },
+                uMaterialProps: { value: null },
             },
             vertexShader,
             fragmentShader,

src/shaders/worldBlur.frag

@@ -6,19 +6,33 @@ in vec2 vUv;
 out vec4 FragColor;
 
 uniform sampler2D tWorld;
+uniform sampler2D uMaterialProps;
 
 const float offset = 1. / WORLD_SIZE * SCENT_BLUR_RADIUS;
 const float repellentOffset = 1. / WORLD_SIZE * REPELLENT_BLUR_RADIUS;
 
+// returns 1.0 if materialId has GAS behavior (pheromone can diffuse through it)
+float isAir(float materialId) {
+    vec4 props = texelFetch(uMaterialProps, ivec2(int(materialId), 0), 0);
+    return props.r == BEHAVIOR_GAS ? 1.0 : 0.0;
+}
+
 void main()	{
     vec4 s0 = texture(tWorld, vUv);
+    float centerAir = isAir(s0.x);
     vec4 s1 = texture(tWorld, vUv + vec2(1, 1) * offset);
     vec4 s2 = texture(tWorld, vUv + vec2(-1, -1) * offset);
     vec4 s3 = texture(tWorld, vUv + vec2(-1, 1) * offset);
     vec4 s4 = texture(tWorld, vUv + vec2(1, -1) * offset);
 
-    float scentToHome = (s0.y + s1.y + s2.y + s3.y + s4.y) / 5. * (1. - SCENT_FADE_OUT_FACTOR);
-    float scentToFood = (s0.z + s1.z + s2.z + s3.z + s4.z) / 5. * (1. - SCENT_FADE_OUT_FACTOR);
+    float a1 = isAir(s1.x);
+    float a2 = isAir(s2.x);
+    float a3 = isAir(s3.x);
+    float a4 = isAir(s4.x);
+
+    float scentCount = 1.0 + a1 + a2 + a3 + a4;
+    float scentToHome = (s0.y + s1.y * a1 + s2.y * a2 + s3.y * a3 + s4.y * a4) / scentCount * (1. - SCENT_FADE_OUT_FACTOR) * centerAir;
+    float scentToFood = (s0.z + s1.z * a1 + s2.z * a2 + s3.z * a3 + s4.z * a4) / scentCount * (1. - SCENT_FADE_OUT_FACTOR) * centerAir;
 
     // repellent channel uses its own diffusion radius and decay rate
     vec4 rr0 = texture(tWorld, vUv);
@@ -26,7 +40,14 @@ void main()	{
     vec4 rr2 = texture(tWorld, vUv + vec2(-1, -1) * repellentOffset);
     vec4 rr3 = texture(tWorld, vUv + vec2(-1, 1) * repellentOffset);
     vec4 rr4 = texture(tWorld, vUv + vec2(1, -1) * repellentOffset);
-    float repellent = (rr0.w + rr1.w + rr2.w + rr3.w + rr4.w) / 5. * (1. - REPELLENT_FADE_OUT_FACTOR);
+
+    float b1 = isAir(rr1.x);
+    float b2 = isAir(rr2.x);
+    float b3 = isAir(rr3.x);
+    float b4 = isAir(rr4.x);
+
+    float repellentCount = 1.0 + b1 + b2 + b3 + b4;
+    float repellent = (rr0.w + rr1.w * b1 + rr2.w * b2 + rr3.w * b3 + rr4.w * b4) / repellentCount * (1. - REPELLENT_FADE_OUT_FACTOR) * centerAir;
 
     FragColor = vec4(
         s0.x,