Tonemapping

tonemap.hlsl

float3 HableToneMap(float3 color)
{
    float A = 0.22;//Shoulder Strength
    float B = 0.30;//Linear Strength
    float C = 0.10;//Linear Angle
    float D = 0.20;//Toe Strength
    float E = 0.01;//Toe Numerator
    float F = 0.30;//Toe Denominator

    color = max(0, color - 0.004f);
    color = ((color * (A*color+C*B)+D*E)/(color*(A*color+B)+D*F))-(E/F);
    return color;
}

float4 ToneMapPass(float2 TexC : TEXCOORD) : SV_TARGET
{
    // Get average luminance
    float3 Color = gImage.Sample(gPointSampler, TexC).xyz;

    // This should be a per-vertex opeartion, since it's constant
    float AvgLuminance = exp(gLuminanceMap.SampleLevel(gPointSampler, float2(0, 0), 9));
    AvgLuminance = max(AvgLuminance, 0.001f);
    Color *= gMiddleGray / AvgLuminance;

    float TonedWhite = HableToneMap(gWhiteLevel.xxx);
     Color = HableToneMap(Color)/TonedWhite.xxx;
}