public override float Lambda(Vector3 <float> w)
{
var absTanTheta = Math.Abs(BxDF.TanTheta(w));
if (float.IsInfinity(absTanTheta))
{
return(0);
}
var alpha = MathF.Sqrt(BxDF.Cos2Phi(w) * alphaX * alphaX + BxDF.Sin2Phi(w) * alphaY * alphaY);
var alpha2Tan2Theta = (alpha * absTanTheta) * (alpha * absTanTheta);
return((-1 + MathF.Sqrt(1 + alpha2Tan2Theta)) / 2.0f);
}
public override float D(Vector3 <float> wh)
{
var tan2Theta = BxDF.Tan2Theta(wh);
// Special case: tan² converges to infinity (at grazing angles)
if (float.IsInfinity(tan2Theta))
{
return(0);
}
var cos2Theta = BxDF.Cos2Theta(wh);
return
(MathF.Exp(-tan2Theta * (BxDF.Cos2Phi(wh) / (alphaX * alphaX) + BxDF.Sin2Phi(wh) / (alphaY * alphaY))) /
(MathUtils.Pi * alphaX * alphaY * cos2Theta * cos2Theta));
}
public override float Lambda(Vector3 <float> w)
{
var absTanTheta = Math.Abs(BxDF.TanTheta(w));
if (float.IsInfinity(absTanTheta))
{
return(0);
}
var alpha = MathF.Sqrt(BxDF.Cos2Phi(w) * alphaX * alphaX + BxDF.Sin2Phi(w) * alphaY * alphaY);
var a = 1.0f / (alpha / absTanTheta);
if (a >= 1.6f)
{
return(0);
}
return((1 - 1.259f * a + 0.396f * a * a) / (3.535f * a + 2.181f * a * a));
}