code / hill-noise

   1 #define TAU 6.283185307179586476925286766559005768394338798750211641949
   2 #define MAX_RESOLUTION 64
   3 extern int resolution;
   4 extern float sigma;
   5 extern float amplitudes[MAX_RESOLUTION];
   6 extern float offsets[MAX_RESOLUTION];
   7 extern float range_min, range_max;
   8 extern bool draw_outline = false;
   9 
  10 float cdf(float x) {
  11     return .5 + .5*sign(x)*sqrt(1.-exp(-4./TAU * x*x));
  12 }
  13 
  14 float noise1d(float x) {
  15     float noise = 0.;
  16     for (int i=0; i < resolution; i++) {
  17         float a = amplitudes[i];
  18         noise += a*cos(x/a + offsets[i]);
  19     }
  20     return cdf(noise/sigma);
  21 }
  22 
  23 vec4 effect(vec4 color, Image texture, vec2 texture_coords, vec2 pixel_coords)
  24 {
  25     float x = mix(range_min,range_max,texture_coords.x);
  26     float n = noise1d(x);
  27     if (draw_outline) {
  28         return texture_coords.y > (1.-n) ? vec4(1.,1.,1.,1.) : vec4(0.,0.,0.,1.);
  29     } else {
  30         return vec4(n,n,n,1.);
  31     }
  32 }