#define D 128
//#define Dper4Pi 14.33

struct VertexOut
{
	float4 Position				:POSITION;
	float4 Color				:COLOR0;
	float2 TexCoord				:TEXCOORD;
	int ID						:TEXCOORD1;	
};


VertexOut VertexProgram(
		  float4 Position   : POSITION,
          float2 TexCoord	: TEXCOORD0,
          float4 Color		: COLOR0,         			
          uniform float4x4 ModelViewProj:state.matrix.mvp			
          )
{
	VertexOut Out;	
	
	Out.TexCoord=TexCoord;
	//Out.Position=mul(ModelViewProj, Position);
	Out.Position=Position;
	Out.ID=TexCoord.x;
	return Out;	
}

float4 FragmentProgram(VertexOut In,
					uniform samplerRECT IllumTexture,
					uniform samplerRECT TauTexture,						
					uniform samplerRECT VisMap,
					uniform samplerRECT DirectIllumTexture,
					uniform samplerRECT Phase,						
					uniform float4 EyeDirsWeights ,
					uniform float3 Alb_Op) : COLOR
{
	
		float4 Color=float4(0,0,0,1);
			
		int particle=In.ID;
		int direction=floor(EyeDirsWeights.x);
		float4 I;
		
		float ds=texRECT(VisMap,float2(particle,direction)).g;
		float tau=texRECT(TauTexture,float2(particle,1)).r;
		float alpha=1-exp(-ds*tau);
		//float alpha=Alb_Op.y;
				
		I=texRECT(IllumTexture,float2(particle,direction));
		Color=texRECT(DirectIllumTexture,float2(particle,direction))+(1-alpha)*I;
						
		for(int d=0;d<D;d++)
		{
				I=texRECT(IllumTexture,float2(particle,d));
				Color+=I*(alpha*Alb_Op.z*texRECT(Phase,float2(d,direction)).r);
		}
			
		
		return  Color;       
}