// OBS Default
uniform float4x4 ViewProj;

// Settings (Shared)
uniform texture2d u_image;
uniform float2 u_imageSize;
uniform float2 u_imageTexel;
uniform int u_radius;
uniform int u_diameter;
uniform float2 u_texelDelta;

// Settings (Private)
uniform float bilateralSmoothing;
uniform float bilateralSharpness;

sampler_state textureSampler {
	Filter    = Point;
	AddressU  = Clamp;
	AddressV  = Clamp;
	MinLOD    = 0;
	MaxLOD    = 0;
};

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) {
	// First part is Bilateral function (1.0 / (o * sqrt(2.0 * pivalue))) with o = 1
	return 0.39894 * exp(-0.5 * dot(v,v) / (sigma*sigma)) / sigma;
}

float4 BlurFunc(float2 uv, float4 rgba) {
	float2 uvOffset = float2(0, 0);

	float Z = 0.0;
	float bZ = 1.0 / Bilateral(0.0, bilateralSharpness);
	float3 color = float3(0, 0, 0);
	for (int k = 1; k <= u_radius; k++) {
		uvOffset += u_texelDelta;

		// Bilateral Kernel
		float bKernel = Bilateral(abs(k), bilateralSmoothing);
		bKernel *= bKernel;
		float bZKernel = bZ  * bKernel;

		// Sample Color
		float3 l_p = u_image.SampleLevel(textureSampler, uv + uvOffset, 0).rgb;
		float3 l_n = u_image.SampleLevel(textureSampler, uv - uvOffset, 0).rgb;

		// Bilateral Stuff
		float l_factor_p = Bilateral3(l_p - rgba.rgb, bilateralSharpness) * bZKernel;
		float l_factor_n = Bilateral3(l_n - rgba.rgb, bilateralSharpness) * bZKernel;
		Z = Z + l_factor_p + l_factor_n;

		// Store Color
		color += l_p * l_factor_p;
		color += l_n * l_factor_n;
	}

	return float4(color.rgb / Z, rgba.a);
}

float4 PSBilateral(VertDataOut v_in) : TARGET {
	float4 rgba = u_image.SampleLevel(textureSampler, v_in.uv, 0);	
	return BlurFunc(v_in.uv, rgba);
}

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