// This is C7E6f_dispersion from "The Cg Tutorial" (Addison-Wesley, ISBN
// 0321194969) by Randima Fernando and Mark J. Kilgard.  See page 195.

void C7E6f_dispersion(float  reflectionFactor : COLOR,
                      float3 R                : TEXCOORD0,
                      float3 TRed             : TEXCOORD1,
                      float3 TGreen           : TEXCOORD2,
                      float3 TBlue            : TEXCOORD3,

                  out float4 color : COLOR,

              uniform samplerCUBE environmentMap0,
              uniform samplerCUBE environmentMap1,
              uniform samplerCUBE environmentMap2,
              uniform samplerCUBE environmentMap3)
{
  // Fetch the reflected environment color
  float4 reflectedColor = texCUBE(environmentMap0, R);

  // Compute the refracted environment color
  float4 refractedColor;
  refractedColor.x = texCUBE(environmentMap1, TRed).x;
  refractedColor.y = texCUBE(environmentMap2, TGreen).y;
  refractedColor.z = texCUBE(environmentMap3, TBlue).z;
  refractedColor.w = 1;

  // Compute the final color
  color = lerp(refractedColor, 
               reflectedColor, 
               reflectionFactor);
}