Texture2D DiffuseTexture;
Texture2D DepthTexture;

float2 Center = { 0.5, 0.5 };
float BlurWidth;
float BlurStart = 1.0f;
float NumberOfSamples = 32;

struct VS_INPUT
{
    float4 Pos : POSITION;
    float2 Tex : TEXCOORD;
};

struct PS_INPUT
{
    float4 Pos : SV_POSITION;
    float2 Tex : TEXCOORD;
};

shared SamplerState Sampler
{
    Filter = MIN_MAG_MIP_LINEAR;
    AddressU = Border;
    AddressV = Border;
};

BlendState NoBlend
{
    AlphaToCoverageEnable = FALSE;
    BlendEnable[0] = FALSE;
};

DepthStencilState EnableDepthWrites
{
    DepthEnable = TRUE;
    DepthWriteMask = ALL;
};

PS_INPUT VS(VS_INPUT input)
{
    PS_INPUT output = (PS_INPUT)0;
    output.Pos = input.Pos;
    output.Tex = input.Tex;

    return output;
}

float4 PS(PS_INPUT input) : SV_Target
{
    float2 UV = input.Tex - Center;
    float4 color = 0;
    for (int i = 0; i < NumberOfSamples; i++)
    {
        float scale = BlurStart - BlurWidth*(i / (float)(NumberOfSamples - 1));
        color += DiffuseTexture.Sample(Sampler, UV * scale + Center);
    }
    color /= NumberOfSamples;
    return color;
}

technique10 Render
{
    pass P0
    {
        SetVertexShader(CompileShader(vs_5_0, VS()));
        SetGeometryShader(NULL);
        SetPixelShader(CompileShader(ps_5_0, PS()));
        SetDepthStencilState(EnableDepthWrites, 0);
        SetBlendState(NoBlend, float4(0, 0, 0, 0), 0xFFFFFFF);
    }
}