source: GTP/trunk/App/Demos/Illum/Illumination Networks Demo [OpenGL]/src/Interpol_LightIlluminatePrograms.cg @ 845

struct VertexOut
{
        float4 Position         :POSITION;
        float2 TexCoord                 :TEXCOORD;      
};


/*
  Vertex program for cloud rendering 
*/
VertexOut VertexProgram( float4 Position :POSITION,
                                                float2 TexCoord:TEXCOORD,
                                                uniform float4x4 ModelViewProj  :state.matrix.mvp
                                                )                                                                       
{
        VertexOut Out;  
        
        Out.TexCoord=TexCoord;
        Out.Position=mul(ModelViewProj, Position);
        Out.TexCoord.y=1-Out.TexCoord.y;
                
        return Out;     
}

/*
  Fragment program for cloud rendering 
*/
float3 FragmentProgram( VertexOut       In,
                                                uniform sampler1D PosTex,
                                                uniform sampler2D PhaseTex,
                                                uniform sampler2D LVisMap,
                                                uniform sampler2D DirMap,
                                                uniform float3 LightRad,
                                                uniform float3 LightPosition):COLOR
{
        const float eps=0.001;
        float3 Color=float3(0,0,0);     
        float3 ParticlePos=tex1D(PosTex,In.TexCoord.x).rgb;
        
        ParticlePos=float3(0,0,0);
        float3 toLight=ParticlePos-LightPosition;
        float3 dir0=normalize(toLight);
        
        float2 angles;
        angles.y=asin(dir0.y); // -pi/2 -- pi/2
                
        float2 d=normalize(dir0.xz);
        angles.x=acos(d.x)*sign(d.y); // -pi -- pi
        angles.x=angles.x/6.28+0.5; // 0 -- 1
        angles.y=angles.y/3.14+0.5; // 0 -- 1
                
        float nearestdir=tex2D(DirMap,angles).r;
        float nearestdir2=tex2D(DirMap,angles).g;
        float weight1=tex2D(DirMap,angles).b;
        float weight2=tex2D(DirMap,angles).a;
        
        if(tex2D(LVisMap,float2(In.TexCoord.x,nearestdir)).r!=0)
        {
                Color+=LightRad*weight1*tex2D(PhaseTex,float2(nearestdir,In.TexCoord.y)).r*0.6;
        }       
        
        if(tex2D(LVisMap,float2(In.TexCoord.x,nearestdir2)).r!=0)
        {
                Color+=LightRad*weight2*tex2D(PhaseTex,float2(nearestdir2,In.TexCoord.y)).r*0.6;
        }
        
        if(abs(In.TexCoord.y-(1-nearestdir))<eps)
        {
                Color+=LightRad*weight1*0.8;
        }
        
        if(abs(In.TexCoord.y-(1-nearestdir2))<eps)
        {
                Color+=LightRad*weight2*0.8;
        }
        
        //Color+=float3(0.01,0.01,0.01);//emission
        return Color;
}