progs/glsl/CH18-mandel.frag

   1 //
   2 // Fragment shader for drawing the Mandelbrot set
   3 //
   4 // Authors: Dave Baldwin, Steve Koren, Randi Rost
   5 //          based on a shader by Michael Rivero
   6 //
   7 // Copyright (c) 2002-2005: 3Dlabs, Inc.
   8 //
   9 // See 3Dlabs-License.txt for license information
  10 //
  11
  12 varying vec3  Position;
  13 varying float LightIntensity;
  14
  15 uniform float MaxIterations;
  16 uniform float Zoom;
  17 uniform float Xcenter;
  18 uniform float Ycenter;
  19 uniform vec3  InnerColor;
  20 uniform vec3  OuterColor1;
  21 uniform vec3  OuterColor2;
  22
  23 void main()
  24 {
  25     float   real  = Position.x * Zoom + Xcenter;
  26     float   imag  = Position.y * Zoom + Ycenter;
  27     float   Creal = real;   // Change this line...
  28     float   Cimag = imag;   // ...and this one to get a Julia set
  29
  30     float r2 = 0.0;
  31     float iter;
  32
  33 //    for (iter = 0.0; iter < MaxIterations && r2 < 4.0; ++iter)
  34     for (iter = 0.0; iter < 12.0 && r2 < 4.0; ++iter)
  35     {
  36         float tempreal = real;
  37
  38         real = (tempreal * tempreal) - (imag * imag) + Creal;
  39         imag = 2.0 * tempreal * imag + Cimag;
  40         r2   = (real * real) + (imag * imag);
  41     }
  42
  43     // Base the color on the number of iterations
  44
  45     vec3 color;
  46
  47     if (r2 < 4.0)
  48         color = InnerColor;
  49     else
  50         color = mix(OuterColor1, OuterColor2, fract(iter * 0.05));
  51
  52     color *= LightIntensity;
  53
  54     gl_FragColor = vec4(color, 1.0);
  55 }