source: GTP/branches/IllumWPdeliver2008dec/IlluminationWP/demos/Standalone/Hierarchical Systems Demo [OpenGL]/src/Psystem_Default_Depth.cg @ 3255

struct VertexOut
{
        float4 VertexPosition           :POSITION;
        float2 TexCoord                         :TEXCOORD;
        float4 Position                         :TEXCOORD1;
        float4 EyePosition                      :TEXCOORD2;
        float2 BbSizeAngleCos           :TEXCOORD3;
        float4 LightSpacePos            :TEXCOORD4;     
        float4 Color                            :COLOR0;
};


//
//  Vertex program for displaying particle system with rectangle rendertexture 
//
VertexOut VertexProgram( float4 Position :POSITION,
                                                float4 Texcoord: TEXCOORD,
                                                float4 Color:COLOR0,
                                                uniform float4x4 ModelViewProj  :state.matrix.mvp,
                                                uniform float4x4 ModelViewMatrix:state.matrix.modelview
                                                )                                                                       
{
        VertexOut Out;  
                        
        Out.Color=Color;
        
        Out.VertexPosition=mul(ModelViewProj, Position);
        Out.TexCoord=Texcoord.xy;
                
        Out.Position=Out.VertexPosition;
        Out.BbSizeAngleCos.x=Texcoord.z;
                
        Out.EyePosition=mul(ModelViewMatrix, Position);
        
        Out.Position.xyz=(Out.Position.xyz/Out.Position.w+1)/2;
        
        return Out;     
}

//
//  Fragment program for displaying particle system with rectangle rendertexture
//
void FragmentProgram(   VertexOut       In,
                                                uniform samplerRECT FrontTexture,
                                                uniform samplerRECT ObjTexture,
                                                uniform float Transparency,
                                                uniform float3 LightColor,
                                                float4 out Color:COLOR                                          
                                        )
{               
        
        float objdepth=texRECT(ObjTexture,In.Position.xy*512).r;
        
        In.TexCoord*=256;
        
        float depth=texRECT(FrontTexture,In.TexCoord).r;
        float density=1;                
        
        if(depth.x==1)
        {
                Color=float4(0,0,0,1);  
        }
        else
        {                       
                float size=0.5*In.BbSizeAngleCos.x;
                float frontdepth=-In.EyePosition.z-size+texRECT(FrontTexture,In.TexCoord).r*size;
                float backdepth=-In.EyePosition.z-size+(1-texRECT(FrontTexture,In.TexCoord).g)*size;
                
                float d=backdepth-frontdepth;
                float o=-objdepth-frontdepth;           
                
                density*=texRECT(FrontTexture,In.TexCoord).a;//density  
                density*=saturate(o/d); 
                                        
                float realdens=density*Transparency;
                                        
                Color=float4(LightColor*realdens*In.Color.rgb,1-realdens);
        }
                
}