GLSL Shader 笔记

float EncodeShadingModelIdAndSelectiveOutputMask(uint ShadingModelId, uint SelectiveOutputMask)
{
    uint Value = (ShadingModelId & SHADINGMODELID_MASK) | SelectiveOutputMask;
    return (float)Value / (float)0xFF;
}

uint DecodeShadingModelId(float InPackedChannel)
{
    return ((uint)round(InPackedChannel * (float)0xFF)) & SHADINGMODELID_MASK;
}

uint DecodeSelectiveOutputMask(float InPackedChannel)
{
    return ((uint)round(InPackedChannel * (float)0xFF)) & ~SHADINGMODELID_MASK;
}

UE4的把float 转uint，或者uint转float代码

float Luminance(vec3 color)
{
    return dot(color,vec3(0.299f, 0.587f, 0.114f));
}

这是神秘海域的tonemap公式：
vec3 ACESFilm(vec3 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));
}