weird: added fractal brownian motion

weird/fbm.glsl

@@ -0,0 +1,67 @@
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+uniform vec2 u_resolution;
+uniform vec2 u_mouse;
+uniform float u_time;
+
+float random (in vec2 st) { 
+    return fract(sin(dot(st.xy,
+                         vec2(12.9898,78.233)))* 
+        43758.5453123);
+}
+
+float noise (in vec2 st) {
+    vec2 i = floor(st);
+    vec2 f = fract(st);
+
+    float a = random(i);
+    float b = random(i + vec2(1.0, 0.0));
+    float c = random(i + vec2(0.0, 1.0));
+    float d = random(i + vec2(1.0, 1.0));
+
+    vec2 u = f * f * (3.0 - 2.0 * f);
+
+    return mix(a, b, u.x) + 
+            (c - a)* u.y * (1.0 - u.x) + 
+            (d - b) * u.x * u.y;
+}
+
+#define OCTAVES 10
+float fbm (in vec2 st) {
+    float value = 0.0;
+    float amplitud = .5;
+    float frequency = 0.;
+    
+    for (int i = 0; i < OCTAVES; i++) {
+        value += amplitud * noise(st);
+        st *= 2.;
+        amplitud *= .7;
+    }
+    return value;
+}
+
+
+vec3 circle(in vec2 _st, in float _radius, vec3 color){
+    vec2 dist = _st-vec2(0.5);
+    return color-smoothstep(_radius-(_radius*0.02),
+                         _radius+(_radius*0.02),
+                         dot(dist,dist)*4.0);
+}
+
+void main() {
+    vec2 st = gl_FragCoord.xy/u_resolution.xy;
+    st*=5.;
+    st.x *= u_resolution.x/u_resolution.y;
+
+    vec3 color = vec3(0.);
+    color += fbm(st*3.0);
+    float resmin = min(u_resolution.x, u_resolution.y);
+    color -=  smoothstep(0.44, 0.48, distance(gl_FragCoord.xy/resmin, (u_resolution/2.)/resmin));
+
+    
+    
+
+    gl_FragColor = vec4(color,1.0);
+}