uniform float4x4 ViewProj;
uniform texture2d image;
uniform float2 texel;
uniform int widthHalf;
uniform int width;
uniform float bilateralSmoothing;
uniform float bilateralSharpness;

sampler_state textureSampler {
	Filter    = Point;
	AddressU  = Clamp;
	AddressV  = Clamp;
};

struct VertDataIn {
	float4 pos : POSITION;
	float2 uv  : TEXCOORD0;
};

struct VertDataOut {
	float4 pos : POSITION;
	float2 uv  : TEXCOORD0;
};

VertDataOut VSDefault(VertDataIn v_in)
{
	VertDataOut vert_out;
	vert_out.pos = mul(float4(v_in.pos.xyz, 1.0), ViewProj);
	vert_out.uv  = v_in.uv;
	return vert_out;
}

// Bilateral Blur
float Bilateral(float x, float sigma)
{
	return 0.39894 * exp(-0.5 * (x*x) / (sigma*sigma)) / sigma;
}

float Bilateral3(float3 v, float sigma)
{
	return 0.39894 * exp(-0.5 * dot(v,v) / (sigma*sigma)) / sigma;
}

float4 PSBilateral(VertDataOut v_in) : TARGET
{
	float4 source = image.Sample(textureSampler, v_in.uv);	
	
	float3 color = float3(0, 0, 0);
	float2 rootuv = v_in.uv - (texel * widthHalf);
	float Z = 0.0;
	float bZ = 1.0 / Bilateral(0.0, bilateralSharpness);
	for (int k = -widthHalf; k <= widthHalf; k++) {
		// Sample Color
		float3 sample = image.Sample(textureSampler, rootuv);
		
		// Bilateral Stuff
		float bKernel = Bilateral(abs(k), bilateralSmoothing);
		bKernel *= bKernel;		
		float factor = Bilateral3(sample - source.rgb, bilateralSharpness) * bZ * bKernel;
		Z += factor;
		
		// Store Color
		color += factor * sample;
		
		// Advance UV
		rootuv += texel;
	}
	
	return float4(color.rgb / Z, source.a);
}

technique Draw
{
	pass
	{
		vertex_shader = VSDefault(v_in);
		pixel_shader  = PSBilateral(v_in);
	}
}