ACES Filmic Tone Mapping Curve の近似の近似

ACES Filmic Tone Mapping Curve(Krzysztof Narkowicz)

float3 ACESFilm(float3 x)
{
    float a = 2.51f;
    float b = 0.03f;
    float c = 2.43f;
    float d = 0.59f;
    float e = 0.14f;
    return saturate((x*(a*x+b))/(x*(c*x+d)+e));
}

の近似. 定義域を[0 2]に狭める.

//domain x: [0 2]
float3 ACESFilmApprox(float3 x)
{
    return -0.053173 + x*(2.170622 + x*(-2.132296 + x*(0.996822 + x*-0.176583)));
}