progs/glsl/shadowtex.frag

   1 // Fragment shader for 2D texture with shadow attenuation
   2 // Brian Paul
   3
   4
   5 uniform sampler2D tex2d;
   6 uniform vec3 lightPos;
   7
   8 void main()
   9 {
  10    // XXX should compute this from lightPos
  11    vec2 shadowCenter = vec2(-0.25, -0.25);
  12
  13    // d = distance from center
  14    float d = distance(gl_TexCoord[0].xy, shadowCenter);
  15
  16    // attenuate and clamp
  17    d = clamp(d * d * d, 0.0, 2.0);
  18
  19    // modulate texture by d for shadow effect
  20    gl_FragColor = d * texture2D(tex2d, gl_TexCoord[0].xy, 0.0);
  21 }