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//	Photoshop style layer blending - multiply

float4x4 WorldViewProjection  : WORLDVIEWPROJECTION;

//Textures

sampler2D tex1Sampler : register (s[0]) = sampler_state
{
	//Texture = <tex1>; Unnecessary due to register (s[0]) which binds the sampler to a specific stage ( in this case 0).
};

sampler2D tex2Sampler : register (s[1]) = sampler_state
{
};

//Mapping
float4x4 TexMap[8] 
< 
	string SasBindAddress = "Ventuz.Textures[*].Mapping"; 
>;


// Vertex shader program input
struct VS_INPUT
{
	float4 Position : POSITION;
	float2 tex1co	: TEXCOORD0;
};


// Vertex shader program output
struct VS_OUTPUT
{
	float4 Position : POSITION;
	float2 tex1co	: TEXCOORD0;
};


// Vertex Shader Program

VS_OUTPUT VS( VS_INPUT Input )
{
	VS_OUTPUT Output;

	// Transform the vertex from 3D object space to 2D screen space.
	Output.Position = mul(Input.Position, WorldViewProjection);

	//Pass Texture Coordinates
	Output.tex1co = Input.tex1co;
	
	return Output;
}

//Pixel Shader Programs

float4 PS_Normal( VS_OUTPUT Input ) :COLOR
{
	//Apply mapping to texture coordinates by multiplying TC as a float4 vector with mapping matrix; get texture from sampler
	float4 col1 = tex2D(tex1Sampler, mul(float4(Input.tex1co, 1.0, 0.0), TexMap[0]).xy);
	float4 col2 = tex2D(tex2Sampler, mul(float4(Input.tex1co, 1.0, 0.0), TexMap[1]).xy);
	
	return float4((col2.a * (col2) + (1.0f - col2.a) * col1).rgb, col1.a);	
}

float4 PS_Multiply( VS_OUTPUT Input ) : COLOR
{
	//Apply mapping to texture coordinates by multiplying TC as a float4 vector with mapping matrix; get texture from sampler
	float4 col1 = tex2D(tex1Sampler, mul(float4(Input.tex1co, 1.0, 0.0), TexMap[0]).xy);
	float4 col2 = tex2D(tex2Sampler, mul(float4(Input.tex1co, 1.0, 0.0), TexMap[1]).xy);
	
	//Multiply blend 
	//Step by step:
	//float3 rgb1 = float3(col1.r,col1.g,col1.b);
	//float3 rgb2 = float3(col2.r,col2.g,col2.b);
	//float alpha2 = col2.a;
	//
	//float3 fill;
	//fill = alpha2 * ( rgb1 * rgb2 ) + (1.0f-alpha2) * rgb1;
	//float4 fin = float4(fill, col1.a);
	//
	//return fin;
	
	// Same operation in one line:
	return float4((col2.a * (col1 * col2) + (1.0f - col2.a) * col1).rgb, col1.a);
	
}



// Techniques
//
// Techniques are used to support multiple vertex/pixel shader
// implementations in a single shader source file. For example,
// these might be different implementations of the same effect,
// each optimized for a specific hardware. The active technique
// can be switched by changing the "Technique" property in the
// Property Editor.

technique Normal
{
	pass pass0
	{
		vertexshader = compile vs_3_0 VS();
		pixelshader  = compile ps_3_0 PS_Normal();
	}
}

technique Multiply
{
	pass pass0
	{
		vertexshader = compile vs_3_0 VS();
		pixelshader  = compile ps_3_0 PS_Multiply();
	}
}