source: GTP/trunk/App/Demos/Illum/Ogre/Media/materials/programs/GameTools_Caustic.hlsl @ 1094

float readDistanceCubeMap(samplerCUBE dcm, float3 coord)                
{
        float dist = texCUBE(dcm, float3(coord.xy, - coord.z)).r;
        if(dist == 0) dist = 10000; ///sky
        return dist;
}

struct VertOut
{
        float4 hPosition        :POSITION;      
        float2 texCoord         :TEXCOORD;      
        float3 wPosition        :TEXCOORD1;     
};


VertOut deaultVS(float4 position : POSITION,
                float2 texCoord : TEXCOORD0,
                uniform float4x4 worldViewProj,
                uniform float4x4 world)
{
  VertOut OUT;
  OUT.texCoord = texCoord;
  OUT.hPosition = mul(worldViewProj, position);  
  OUT.wPosition = mul(world, position).xyz;
  return OUT;    
}

float4 deaultPS(VertOut IN,
                                uniform samplerCUBE CubeMap : register(s0),
                                uniform samplerCUBE distanceCube : register(s1),
                                uniform float3 cubeMapCameraPosition,
                                uniform float attenuation):COLOR
{
        float4 Color = float4(1,1,1,1); 
        
        float3 dir = IN.wPosition - cubeMapCameraPosition;
        float4 caustic = texCUBE(CubeMap, float3(dir.xy,-dir.z) );
        float mydist = length(dir);
        float dist = readDistanceCubeMap(distanceCube, dir);
        
        float EPSILON = 1.0;

        if(mydist > dist + EPSILON) caustic = 0;
        //caustic.rgb *= max(attenuation - mydist, 0.0) / attenuation;
                        
        Color = caustic;
        Color += attenuation;
        Color.a = 1;    
        return Color;
}