grayscale.fx

// Grayscale post-processing effect
// AJ Weeks 2017

Texture2D gTexture;
float gIntensity;

SamplerState samPoint
{
    Filter = MIN_MAG_MIP_POINT;
    AddressU = Mirror;
    AddressV = Mirror;
};

RasterizerState BackfaceCull
{
    CullMode = NONE;
};

BlendState DisableBlending
{
    BlendEnable[0] = FALSE;
};

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

//IN / OUT STRUCTS
//----------------
struct VS_INPUT
{
    float3 Position : POSITION;
    float2 TexCoord : TEXCOORD0;
};

struct PS_INPUT
{
    float4 Position : SV_POSITION;
    float2 TexCoord : TEXCOORD1;
};


//VERTEX SHADER
//-------------
PS_INPUT VS(VS_INPUT input)
{
    PS_INPUT output = (PS_INPUT)0;

    output.Position = float4(input.Position, 1.0);
    output.TexCoord = input.TexCoord;
    
    return output;
}

//PIXEL SHADER
//------------
float4 PS(PS_INPUT input): SV_Target
{
    float4 sam = gTexture.Sample(samPoint, input.TexCoord);
    float mean = 0.21 * sam.r + 0.72 * sam.g + 0.07 * sam.b;

    return float4(lerp(sam.rgb, float3(mean, mean, mean), gIntensity), 1.0f);
}

//TECHNIQUE
//---------
technique11 Grayscale
{
    pass P0
    {
        SetRasterizerState(BackfaceCull);
        SetDepthStencilState(EnableDepth, 0);
        SetBlendState(DisableBlending, float4(0.0f, 0.0f, 0.0f, 0.0f), 0xFFFFFFFF);
        SetVertexShader( CompileShader( vs_4_0, VS() ) );
        SetGeometryShader( NULL );
        SetPixelShader( CompileShader( ps_4_0, PS() ) );
    }
}