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Sierpinski tetrahedron attempt

matrefeytontias May 19th, 2016 77 Never
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  1. #define DE_ITER 10
  2. #define MARCHING_ITER 64
  3. #define MARCHING_THRESHOLD 10e-6
  4.  
  5. vec3 camera = vec3(0., 1., -5.);
  6.  
  7. float d_sierpinski_tetrahedron(vec3 z)
  8. {
  9.     float Scale = 0.5;
  10.     vec3 a1 = vec3(1,1,1);
  11.     vec3 a2 = vec3(-1,-1,1);
  12.     vec3 a3 = vec3(1,-1,-1);
  13.     vec3 a4 = vec3(-1,1,-1);
  14.     vec3 c;
  15.     int n = 0;
  16.     float dist, d;
  17.     while (n < DE_ITER) {
  18.          c = a1; dist = length(z-a1);
  19.             d = length(z-a2); if (d < dist) { c = a2; dist=d; }
  20.          d = length(z-a3); if (d < dist) { c = a3; dist=d; }
  21.          d = length(z-a4); if (d < dist) { c = a4; dist=d; }
  22.         z = Scale*z-c*(Scale-1.0);
  23.         n++;
  24.     }
  25.  
  26.     return length(z) * pow(Scale, float(-n));
  27. }
  28.  
  29. float d_plane(vec3 p, vec3 e1, vec3 e2, vec3 a)
  30. {
  31.     e1 = normalize(e1);
  32.     e2 = normalize(e2);
  33.     vec3 pp = dot(p, e1) * e1 + dot(p, e2) * e2 + a;
  34.     return length(p - pp);
  35. }
  36.  
  37. float d_sphere(vec3 p, vec3 c, float r)
  38. {
  39.     return length(p - c) - r;
  40. }
  41.  
  42. float DE(vec3 p)
  43. {
  44.     // return d_sphere(p, vec3(cos(time), sin(time), cos(time)), 1.);
  45.     return d_sierpinski_tetrahedron(p);
  46.     // return min(d_plane(p, vec3(1., 0., 0.), vec3(0., 0., 1.), vec3(0.)), d_sphere(p, vec3(cos(time), sin(time), cos(time)), 1.));
  47. }
  48.  
  49. void main()
  50. {
  51.     vec2 uv = (in_uv_coords - vec2(0.5, 0.5)) * 2;
  52.     vec3 dir = normalize(vec3(uv, 1.));
  53.     int i;
  54.     float d = 0;
  55.     bool ended = false;
  56.     for(i = 0; i < MARCHING_ITER; i++)
  57.     {
  58.         vec3 p = camera + d * dir;
  59.         float dd = DE(p);
  60.         d += dd;
  61.         if(abs(dd) < MARCHING_THRESHOLD)
  62.         {
  63.             ended = true;
  64.             break;
  65.         }
  66.     }
  67.    
  68.     if(ended) gl_FragColor = vec4(1., 1., 1., 0.) * (1. - (float(i) / float(MARCHING_ITER)));
  69.     else gl_FragColor = vec4(0., 0., 0., 0.);
  70. }
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