/// <summary>
/// Computes the distribution of microfacets with the given normal.
/// </summary>
/// <param name="normal">The normal vector of the microfacets, in shading space.</param>
/// <returns>The fraction of microfacets that are oriented with the given normal.</returns>
public float NormalDistribution(Vector3 normal)
{
float tan2Theta = ShadingSpace.TanThetaSqr(normal);
if (float.IsInfinity(tan2Theta))
{
return(0);
}
float cos4Theta = ShadingSpace.CosThetaSqr(normal) * ShadingSpace.CosThetaSqr(normal);
float e = tan2Theta * (
ShadingSpace.CosPhiSqr(normal) / (AlphaX * AlphaX)
+ ShadingSpace.SinPhiSqr(normal) / (AlphaY * AlphaY)
);
return(1 / (MathF.PI * AlphaX * AlphaY * cos4Theta * (1 + e) * (1 + e)));
}
