struct Vertex
{
    float4 pos : POSITION;
    float2 tex : TEXTURE;
    float3 norm : NORMAL;
};

struct PixelShaderArgs
{
    float4 pos : SV_POSITION;
    float2 col : TEXTURE;
    float3 norm : NORMAL;
};

struct GaussianBlurShaderData
{
    float2 Resolution;
    float Intensity;
    float Padding;
};

Texture2D ShaderTexture : register(t0);
SamplerState Sampler : register(s0);
float4x4 localMatrix : register(b0);

cbuffer GaussianBlurShaderDataBuffer : register(b1)
{
    GaussianBlurShaderData GaussianData;
};

PixelShaderArgs VertexShaderMain(Vertex vertex)
{
    PixelShaderArgs output;
    output.pos = vertex.pos;
    output.col = vertex.tex;
    return output;
}

float Curve(float x)
{
    x = x * 2.0 - 1.0;
    return -x * abs(x) * 0.5 + x + 0.5;
}

float4 GaussianBlur(float2 size, float2 uv, float radius)
{
    if (radius >= 1.0)
    {
        float4 a = float4(0,0,0,0);
        float4 c = float4(0,0,0,0);
        float width = 1.0 / size.x;
        float divisor = 0.0;
        float weight = 0.0;
        float multiplier = 1.0 / radius;
        for (float x = -radius; x <= radius; x++)
        {
            a = ShaderTexture.Sample(Sampler, uv + float2(x * width, 0.0));
            weight = Curve(1.0 - (abs(x) * multiplier));
            c += a * weight;
            divisor += weight;
        }
        return float4(c.r / divisor, c.g / divisor, c.b / divisor, 1.0);
    }
    return ShaderTexture.Sample(Sampler, uv);
}

float4 PixelShaderMain(PixelShaderArgs pixelShaderArgs) : SV_Target
{
    float2 uv = pixelShaderArgs.pos.xy / GaussianData.Resolution.xy;
    return GaussianBlur( GaussianData.Resolution.xy, uv, GaussianData.Intensity);
}