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;
}