source: GTP/trunk/App/Demos/Illum/Ogre/Media/PMDemo/PathMapWeightCompute.hlsl @ 2202

#define SAMPLECUTDIST2 0.01
#define WEIGHTCUTOFF 0.01

uniform int nRadionColumns;
uniform sampler2D radionSampler       : register(s0);
uniform sampler2D entryPointCountSampler : register(s1);
uniform sampler2D allWeightsSampler   : register(s2);
uniform float3 lightPos;
uniform float3 lightDir;
uniform float clusterCount;

struct vsInputComputeWeights
{
    float4      pos                     : POSITION;
    float2      tex                     : TEXCOORD0;
};

struct vsOutputComputeWeights
{
    float4      pos                     : POSITION;
    float2      tex                     : TEXCOORD0;
};

vsOutputComputeWeights
        vsComputeWeights(vsInputComputeWeights input)
{
    vsOutputComputeWeights output = (vsOutputComputeWeights)0;
    output.pos = input.pos;
    output.tex = input.tex;
    return output;
}

float4
        psComputeWeights(vsOutputComputeWeights input) : COLOR0
{
        float dataColumnWidth = 1.0 / (float)nRadionColumns;
        int bushIndex = input.tex.x * 4096 + input.tex.y * nRadionColumns * 4096;
        int werx = bushIndex % nRadionColumns;
        int wery = bushIndex / nRadionColumns;
        float3 pos = tex2D(radionSampler, float2((werx + 0.25) * dataColumnWidth, (wery  + 0.5) / 4096.0) ).xyz;
        float3 dir = tex2D(radionSampler, float2((werx + 0.75) * dataColumnWidth, (wery  + 0.5) / 4096.0) ).xyz;
        
        float3 diff = lightPos - pos;
        float dist2 = dot(diff, diff);
        if(dist2 < SAMPLECUTDIST2)
                dist2 = SAMPLECUTDIST2;
        diff = normalize(diff);
        float cosa = max(dot(lightDir, -diff), 0);
        float cosb = max(dot(dir, diff), 0);    
        
        /*
        float4 occProjPos = mul(float4(pos, 1), occWorldToProjMatrix);  
        occProjPos /= occProjPos.w;
        float2 occTexPos = mul( occProjPos.xyw, occProjToTexMatrix);
        float visibility = tex2Dproj(depthMapSampler, float4(occTexPos, occProjPos.z - 0.1, 1) );

        float3 lightToPos = pos - lightPos;
        float actualDepth = length(lightToPos);
*/
        float visibility = 1;
        
        float4 ret = cosa * cosb;

        //return float4(lightDir + ret.x * 0.00000000001, 1);
        return ret;
        //return ret.x*0.0000000001 + 0.5;
}

float4 psSumWeights(vsOutputComputeWeights input) : COLOR0
{
        float halfPixel = 0.5 / clusterCount;
        float iCluster = input.tex.x + halfPixel;
        int entryPointCount = tex2D(entryPointCountSampler, float2(iCluster, 0.25));
        int currentEntryPoint = tex2D(entryPointCountSampler, float2(iCluster, 0.75));
        //sum entrypoint weights
        float weight = 0;
        float clusterRad = 0;
        for(int i = 0; i < entryPointCount; i++)
        {
                float hp = float2(0.5 / (float) nRadionColumns, 0.5 / 4096.0);
                float2 coord1 = float2((float)(currentEntryPoint % nRadionColumns)  / (float) nRadionColumns,
                                                                currentEntryPoint / (float) nRadionColumns / 4096.0) + hp;
                coord1.y = 1.0 - coord1.y;
                float2 coord2 = coord1 + float2(hp.x / 2.0, 0);
                float radrad = tex2Dlod(radionSampler, float4(coord2, 0, 0)).a;
                //weight += tex2Dlod(allWeightsSampler, float4(coord1, 0, 0)).r * radrad;
                weight += tex2Dlod(allWeightsSampler, float4(coord1, 0, 0)).r;
                //clusterRad += radrad;
                currentEntryPoint++;
        }       
        /*
        if(clusterRad >= 0)
                weight /= clusterRad;
        else
                weight = 0;*/
        
    weight /= (float) entryPointCount;
                
        return weight;
}