data/r2c2/sky.shader

   1 vertex_shader "
   2         varying vec3 eye_look_dir;
   3         void main()
   4         {
   5                 vec4 eye_pos = vec4(mat3(gl_ModelViewMatrix)*gl_Vertex.xyz, 1);
   6                 gl_Position = gl_ProjectionMatrix*eye_pos;
   7                 eye_look_dir = eye_pos.xyz;
   8         }";
   9
  10 fragment_shader "
  11         uniform vec3 eye_sky_dir;
  12         uniform vec3 wavelengths;
  13         uniform float scatter_constant;
  14         uniform float sun_intensity;
  15         uniform float sun_size;
  16         varying vec3 eye_look_dir;
  17         float thickness(float c, float r)
  18         {
  19                 float rc = r*c;
  20                 return sqrt(2.0*r+1.0+rc*rc)-rc;
  21         }
  22         float srgb(float c)
  23         {
  24                 if(c<0.0031308)
  25                         return 12.92*c;
  26                 else
  27                         return (1.055)*pow(c, 1.0/2.4)-0.055;
  28         }
  29         void main()
  30         {
  31                 vec3 n_eye_look_dir = normalize(eye_look_dir);
  32                 vec3 n_eye_sun_dir = normalize(gl_LightSource[0].position.xyz);
  33
  34                 if(dot(n_eye_look_dir, eye_sky_dir)>0)
  35                 {
  36                         float look_scale = thickness(dot(n_eye_look_dir, eye_sky_dir), 635.0);
  37                         float sun_scale = thickness(dot(n_eye_sun_dir, eye_sky_dir), 635.0);
  38                         float c = dot(n_eye_look_dir, n_eye_sun_dir);
  39                         float scatter_strength = (1.0+c*c)/2.0;
  40                         vec3 scatter_factor = scatter_constant/pow(wavelengths, vec3(4.0));
  41
  42                         vec3 color;
  43                         float scale_ratio = look_scale/sun_scale;
  44                         if(scale_ratio>0.999 && scale_ratio<1.001)
  45                                 color = sun_intensity*scatter_strength*scatter_factor*sun_scale*exp(-scatter_factor*sun_scale);
  46                         else
  47                                 color = sun_intensity*scatter_strength*(exp(-scatter_factor*sun_scale)-exp(-scatter_factor*look_scale))/(1.0-sun_scale/look_scale);
  48                         if(dot(n_eye_look_dir, n_eye_sun_dir)>cos(sun_size))
  49                                 color += exp(-scatter_factor*look_scale)*sun_intensity;
  50                         gl_FragColor = vec4(srgb(color.r), srgb(color.g), srgb(color.b), 1.0);
  51                 }
  52                 else
  53                         gl_FragColor = vec4(vec3(0.0), 1.0);
  54         }";