/////////
///This example shader demonstrates how to use the sprite particle type added by the GTP to OGRE's particle types.
///These sprites are quads with zero size, they should be scaled and rotated towards the camera by the vertex shader.
///All four vertices of the quad are placed in the center of the particle, the z and w components of their texture coordinates
///gives us the offset they should be moved in camera space (these components store the corner direction multiplied by the particle size).
///The x and y components of the texture coordinates store the defult uv for texturing.
////////
struct VS_OUT
{
	float4 hPosition	: POSITION;
	float4 texCoord		: TEXCOORD0;
	float4 color		: COLOR0;
};

VS_OUT Sprite_VS(float4 position : POSITION,	
		float4 texCoord : TEXCOORD0,
		float4 color 	: COLOR0,
		uniform float4x4 worldView,
		uniform float4x4 Proj)
{
  VS_OUT OUT;
///transform to camera space and create a sprite with vertex offset
   //texCoord.y = 1.0 - texCoord.y;
   float2 offset = texCoord.zw;
   float4 cPosition = mul(worldView, position);
   cPosition.xy += offset;
   
 //  cPosition = float4(100*texCoord.xy,0,1);
 ///projection 
	OUT.hPosition = mul( Proj, cPosition );
   OUT.texCoord = texCoord;
  // OUT.color = float4(offset,1,1.0);
   OUT.color = color;

  return OUT;
}

///Simple texture mapping
float4 Sprite_PS(VS_OUT IN ,
		uniform sampler2D colorTexture : register(s0)):COLOR
{
	return 1;
	return tex2D( colorTexture, IN.texCoord.xy) * IN.color;
}

//////////
///These shaders uses the sprite particle type. They demonstrate the "spherical billboards" (SBB) particle rendering method.
///SBB alter the opacity of a particle according to the objects of the scene it intersects. To find out the correct opacity
///we store scene depth values in a previous step, we assume that the particle is sphere shaped and find the length of the viewray
///that travells inside a particle before reaching an object.
//////////
struct SBB_VS_OUT
{
	float4 hPosition	: POSITION;
	float4 texCoord		: TEXCOORD0;
	float3 P		: TEXCOORD1;
	float3 Q		: TEXCOORD2;
	float r			: TEXCOORD3;
	float2 screenCoord	: TEXCOORD4;	
	float4 color		: COLOR0;
};

SBB_VS_OUT SBB_Sprite_VS (float4 position : POSITION,	
		float4 texCoord : TEXCOORD0,
		float4 color 	: COLOR,
		uniform float width,
		uniform float height,
		uniform float4x4 worldView,
		uniform float4x4 Proj)
{
	SBB_VS_OUT OUT;
 ///transform to camera space and create a sprite with vertex offset 
	float2 offset = texCoord.zw;
	float4 cPosition;   
	float4 wPosition = position;    
	cPosition = mul(worldView, wPosition);
/// P is the particle sphere center	
	OUT.P = cPosition.xyz;
	OUT.P.z = - 1 * OUT.P.z;
	cPosition.xy += offset;
/// Q is the shaded point (it is moved backwards to avoid unwanted frontplane clipping)				
	OUT.Q = cPosition.xyz;	
	OUT.Q.z = OUT.P.z;
	OUT.r = abs(texCoord.z);   
/// calculate screen space position 
   OUT.hPosition = mul( Proj, cPosition );
   OUT.screenCoord =  (OUT.hPosition.xy / OUT.hPosition.w + 1.0) / 2.0;
   OUT.screenCoord.y = 1.0 - OUT.screenCoord.y;
   OUT.screenCoord += float2(0.5/width, 0.5/height);   
   
   OUT.texCoord = texCoord;
   OUT.color = color;

  return OUT;
} 


float4 SBB_Sprite_PS(SBB_VS_OUT IN ,
	//	in screenCoord : VPOS,
	    uniform float nearplane,
	    uniform float farplane,
            uniform float4 color,
	    uniform sampler2D colorTexture : register(s0),
	    uniform sampler2D DepthMap : register(s1),
	    uniform sampler2D PlanckMap : register(s2)
		) : COLOR
{
	float4 Color = IN.color;
	float alpha = 0;
	
/// get the depth values from the depthMap and calculate ray length in sphere	
	float d = length( IN.Q - IN.P );
	float Zs;
	if( d < IN.r )
	{
	 
	 float w = sqrt( IN.r * IN.r - d * d );
	 alpha = w / IN.r;
	 alpha *= pow( (IN.r-d) / IN.r , 2);
	
	 float F = IN.Q.z - w;
	 float B = IN.Q.z + w; 
	 

	 Zs = tex2D( DepthMap, IN.screenCoord ).r;
	 if(Zs == 0) Zs = farplane;
	 float ds = min( Zs, B ) - max( nearplane, F );	 
	// float ds = min( Zs, B ) - F;	 
	 alpha *=  ds / w * 0.5;
	
	
	}
/// fetch opacity from a texture
	Color.a *= tex2D( colorTexture, IN.texCoord.xy).r ;
	//Color.a *= IN.color.a;
	Color.a *= alpha;
/// address a color map (colors of fire eg.) with the alpha
	Color.rgb = tex2D( PlanckMap, Color.aa).rgb;
	
	return Color * color; 
}