cool stuff

shaders/reaction.frag

@@ -0,0 +1,77 @@
+#version 100
+precision mediump float;
+
+uniform float u_time;
+uniform vec2 u_resolution;
+uniform vec2 u_mouse;
+uniform sampler2D u_backbuffer;
+
+// Gray-Scott parameters
+// standard "spots" / coral
+#define DA 1.0
+#define DB 0.5
+#define FEED 0.055
+#define KILL 0.062
+#define DT 1.0
+
+void main() {
+    vec2 pixel = 1.0 / u_resolution;
+    vec2 uv = gl_FragCoord.xy / u_resolution;
+    
+    // Read current state
+    vec4 state = texture2D(u_backbuffer, uv);
+    float a = state.r;
+    float b = state.g;
+    
+    // Laplaclan (convolution)
+    // 0.05  0.2  0.05
+    // 0.2   -1   0.2
+    // 0.05  0.2  0.05
+    
+    vec4 sum = vec4(0.0);
+    sum += texture2D(u_backbuffer, uv + vec2(-1.0, -1.0) * pixel) * 0.05;
+    sum += texture2D(u_backbuffer, uv + vec2( 0.0, -1.0) * pixel) * 0.2;
+    sum += texture2D(u_backbuffer, uv + vec2( 1.0, -1.0) * pixel) * 0.05;
+    
+    sum += texture2D(u_backbuffer, uv + vec2(-1.0,  0.0) * pixel) * 0.2;
+    sum -= state * 1.0;
+    sum += texture2D(u_backbuffer, uv + vec2( 1.0,  0.0) * pixel) * 0.2;
+    
+    sum += texture2D(u_backbuffer, uv + vec2(-1.0,  1.0) * pixel) * 0.05;
+    sum += texture2D(u_backbuffer, uv + vec2( 0.0,  1.0) * pixel) * 0.2;
+    sum += texture2D(u_backbuffer, uv + vec2( 1.0,  1.0) * pixel) * 0.05;
+    
+    // Reaction-Diffusion logic
+    // A' = A + (Da * lapA - A*B*B + f*(1-A)) * dt
+    // B' = B + (Db * lapB + A*B*B - (k+f)*B) * dt
+    
+    float lapA = sum.r;
+    float lapB = sum.g;
+    
+    float abb = a * b * b;
+    
+    float nA = a + (DA * lapA - abb + FEED * (1.0 - a)) * DT;
+    float nB = b + (DB * lapB + abb - (KILL + FEED) * b) * DT;
+    
+    // Clamp
+    nA = clamp(nA, 0.0, 1.0);
+    nB = clamp(nB, 0.0, 1.0);
+    
+    // Mouse Interaction (Add B)
+    float dist = distance(gl_FragCoord.xy, u_mouse);
+    if (dist < 20.0 && u_mouse.x > 0.0) {
+        nB = 0.9;
+    }
+    
+    // Initialization (random noise at start)
+    if (u_time < 0.5) {
+        if (fract(sin(dot(uv, vec2(12.9898, 78.233))) * 43758.5453) > 0.99) {
+            nB = 1.0;
+        } else {
+            nB = 0.0;
+            nA = 1.0;
+        }
+    }
+    
+    gl_FragColor = vec4(nA, nB, 0.0, 1.0);
+}