source: GTP/trunk/App/Demos/Illum/Ogre/Media/materials/programs/GameTools_CauCube.hlsl @ 1355

struct VS_OUT
{
        float4 hPosition        : POSITION;
        float4 color            : COLOR0;       
};

VS_OUT CauVS(float4 position : POSITION,        
                float4 texCoord : TEXCOORD0,
                float4 color    : COLOR0,
                uniform float4x4 worldView,
                uniform float4x4 Proj,
                uniform float resolution,
                uniform sampler2D PhotonHitMap : register(s0))
{
  VS_OUT OUT;
     
  float4 cPosition;
  float pixel = 1.0 / resolution;   
  float2 uv = float2(position.x, 1.0 - position.y);
  float4 pos = tex2Dlod(PhotonHitMap, float4(uv,0,0)).rgba;

   if(pos.a == 0)//no photon hit
   {
                OUT.color = float4(0,0,0,0);            
                OUT.hPosition = float4(0, 0, 100000000, 1);
   }
   else
   {
                float4 wPosition = float4(normalize(pos.xyz),1);    
                cPosition = mul(worldView, wPosition);
                OUT.hPosition = mul(Proj, cPosition);
                
                float intensity = 0.5;
                
                //read four neighbours
                float valids = 0;
                float sumdist = 0;
                float dist;
                float4 pos1 = tex2Dlod(PhotonHitMap, float4(uv + float2(pixel, pixel),0,0)).rgba;
                if(pos1.a != 0)
                {
                        dist = length(pos1.xyz - pos.xyz);
                        valids++;
                        sumdist += dist;
                }
                float4 pos2 = tex2Dlod(PhotonHitMap, float4(uv + float2(-pixel, pixel),0,0)).rgba;
                if(pos2.a != 0)
                {
                        dist = length(pos2.xyz - pos.xyz);
                        valids++;
                        sumdist += dist;
                }
                float4 pos3 = tex2Dlod(PhotonHitMap, float4(uv + float2(pixel, -pixel),0,0)).rgba;
                if(pos3.a != 0)
                {
                        dist = length(pos3.xyz - pos.xyz);
                        valids++;
                        sumdist += dist;
                }
                float4 pos4 = tex2Dlod(PhotonHitMap, float4(uv + float2(-pixel, -pixel),0,0)).rgba;
                if(pos4.a != 0)
                {
                        dist = length(pos4.xyz - pos.xyz);
                        valids++;
                        sumdist += dist;
                }
                
                float avrdist = sumdist / valids;
                float maxdist = 0.1;
                intensity = max(maxdist - avrdist, 0.0) / maxdist;
                
                OUT.color = float4(1,1,1,intensity);
        }  
   
   return OUT;
}


float4 CauPS(VS_OUT IN,
                uniform float3 color ):COLOR
{ 
  return IN.color * float4(color, 1);  
}