code / hill-noise

   1 #define TAU 6.283185307179586476925286766559005768394338798750211641949
   2 #define PHI 1.618033988749894848204586834365638117720309179805762862135
   3 #define MAX_RESOLUTION 64
   4 extern int resolution;
   5 extern float sigma;
   6 extern float amplitudes[MAX_RESOLUTION];
   7 extern vec2 offsets[MAX_RESOLUTION];
   8 extern vec2 range_min, range_max;
   9 
  10 float cdf(float x) {
  11     return .5 + .5*sign(x)*sqrt(1.-exp(-4./TAU * x*x));
  12 }
  13 
  14 float noise2d(vec2 pos) {
  15     float noise = 0.;
  16     for (int i=0; i < resolution; i++) {
  17         float angle = mod(float(i)*PHI, 1.)*TAU;
  18         float u = pos.x*cos(angle) - pos.y*sin(angle);
  19         float v = pos.x*cos(angle+TAU/4.) - pos.y*sin(angle+TAU/4.);
  20         float a = amplitudes[i];
  21         noise += a*mix(cos(u/a + offsets[i].x), cos(v/a + offsets[i].y), .5);
  22     }
  23     return cdf(noise/sigma);
  24 }
  25 
  26 
  27 vec4 effect(vec4 color, Image texture, vec2 texture_coords, vec2 pixel_coords)
  28 {
  29     vec2 coords = mix(range_min,range_max,texture_coords);
  30     float n = noise2d(coords);
  31     return vec4(n,n,n,1.);
  32 }