Texture2D BlurTexture;
SamplerState BlurSampler;

cbuffer ScreenSizeBuffer
{
    float screenHeight;
    float blurAmount;
};

struct VS_to_PS
{
    float4 position : SV_POSITION;
    float2 texCoord0 : TEXCOORD0;
};

static float PixelKernel[9] =
{
    -4.0,
    -3.0,
    -2.0,
    -1.0,
     0.0,
     1.0,
     2.0,
     3.0,
     4.0
};
 
static float BlurWeights[9] =
{
    0.02242,
    0.04036,
    0.12332,
    0.20179,
    0.22422,
    0.20179,
    0.12332,
    0.04036,
    0.02242
};

float4 VerticalBlurPixelShader(VS_to_PS input) : SV_TARGET
{
    float4 color = float4(0.0, 0.0, 0.0, 0.0);
    float texelSize = 1.0 / screenHeight;

    for(int i = 0; i < 9; i++)
    {
	color += BlurTexture.Sample(BlurSampler, input.texCoord0 + float2(0.0, texelSize * PixelKernel[i] * blurAmount)) * BlurWeights[i];
    }
	
    color.a = 1.0f;

    return color;
}