#define D 128

struct VertexOut
{
	float4 VertexPosition		:POSITION;
	float2 TexCoord				:TEXCOORD;
	int ID						:TEXCOORD1;
};


/*
  Vertex program for cloud rendering 
*/
VertexOut VertexProgram( float4 Position :POSITION,
						float2 Texcoord: TEXCOORD
						)									
{
	VertexOut Out;	
	
	Out.VertexPosition=Position;
	Out.TexCoord=Texcoord;
	Out.ID=Texcoord.x;	
	
	return Out;	
}

/*
  Fragment program for cloud rendering 
*/
float3 FragmentProgram(	VertexOut	In,
						uniform samplerRECT LVisMap,
						uniform samplerRECT Phase,
						uniform float4 LightDirsWeights,
						uniform float3 LightRad,
						uniform float3 LightRad2,
						uniform float2 Alb_Op):COLOR
{	
	float3 Color=float3(0,0,0);	
	
	int direction=floor(In.TexCoord.y);
	int negDir=D-1-direction;
	int particle=In.ID;
	
	float a_o=Alb_Op.x*Alb_Op.y;		
	
	//Light1			
	int LDir=floor(LightDirsWeights.x);		
	float isvisible=texRECT(LVisMap,float2(particle,0)).r;
	
	//Scattering
	Color+=isvisible*a_o*texRECT(Phase,float2(LDir,negDir)).r*LightRad;
	//Transmittance	
	if(direction==LDir)
	{
		//Color+=LightRad*(1-Alb_Op.y)*isvisible;
		Color+=LightRad*isvisible;
	}
		
	//Light2			
	int LDir2=floor(LightDirsWeights.y);		
	
	isvisible=texRECT(LVisMap,float2(particle,1)).r;
	//isvisible=1;
	
	//Scattering
	Color+=isvisible*a_o*texRECT(Phase,float2(LDir2,negDir)).r*LightRad2;
	//Transmittance	
	if(direction==LDir2)
	{
		//Color+=LightRad2*(1-Alb_Op.y)*isvisible;
		Color+=LightRad2*isvisible;
	}	
		
	
	///Emission
	//Color+=float3(0.01,0.01,0.01);	
		
	return Color;
}