source: GTP/trunk/App/Demos/Illum/Ogre/Media/PMDemo/PathMapWeightCompute.hlsl @ 2188

#define SAMPLECUTDIST2 0.01
#define WEIGHTCUTOFF 0.01

uniform int nRadionColumns;
uniform sampler2D radionSampler : register(s0);
uniform float3 lightPos;
uniform float3 lightDir;

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 = - dot(lightDir, diff);
        float cosb = dot(dir, diff);    
        
        /*
        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;
        
        float ret;
        if(  visibility < 0.5 || cosa < 0 || cosb < 0)
                ret = 0.0;
        else
                ret = pow(cosa, 9) * cosb / dist2;

        if(ret < 0.000001)
                ret = 0.0;
        
                return 1 + ret * 0.0000000001;
        return float4(ret, ret, ret, ret);
}