struct VertexOut
{
	float4 VertexPosition		: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.VertexPosition=mul(ModelViewProj, Position);
	Out.TexCoord=Texcoord;
	
	return Out;	
}

/*
  Fragment program for cloud rendering 
*/
float3 FragmentProgram(	VertexOut	In,
						uniform samplerRECT IllumTexture,
						uniform samplerRECT VisMap,
						uniform samplerRECT DirectIllum,
						uniform samplerRECT Phase,
						uniform float2 Alb_Op
						):COLOR
{
		
	int thisDir=round(In.TexCoord.y);
	int thisID=round(In.TexCoord.x);
	float3 DirectRad;
	float3 Radin;
	
	float3 Color=float3(0,0,0);
				//texRECT(IllumTexture,float2(thisID,thisDir)).rgb;
	
	int visibleID=round(texRECT(VisMap,float2(thisID,thisDir)).r);
	
	if(visibleID<512)		
	{
		DirectRad=texRECT(DirectIllum,float2(visibleID,thisDir)).rgb;
		Radin=texRECT(IllumTexture,float2(visibleID,thisDir)).rgb;
		
		Color+=(1-Alb_Op.y)*(Radin+DirectRad);
	}
		
	float a_o=Alb_Op.x*Alb_Op.y*1.0/4.0;
	
	for(int d=0;d<4;d++)
	{
		visibleID=round(texRECT(VisMap,float2(thisID,d)).r);
		
		if(visibleID<4)		
		{
			DirectRad=texRECT(DirectIllum,float2(visibleID,thisDir)).rgb;
			Radin=texRECT(IllumTexture,float2(visibleID,d));
			Color+=(Radin+DirectRad)*a_o*texRECT(Phase,float2(d,thisDir)).r;
		}
	}
				
	return Color;
}