I have been going through some of the shader code and I keep coming across this rcp() and I have no idea what it does or is supposed to do. Where can I find the definition of this function?
I was looking at this post Physically Based Shading on Mobile - Unreal Engine and at the bottom the code references this function. Thanks for your help
half D_Approx( half Roughness, half RoL )
{
half a = Roughness * Roughness;
half a2 = a * a;
float rcp_a2 = rcp(a2);
// 0.5 / ln(2), 0.275 / ln(2)
half c = 0.72134752 * rcp_a2 + 0.39674113;
return rcp_a2 * exp2( c * RoL - c );
}