private void EvalBrdf(out RgbSpectrum fs, ref Vector lwi, ref Vector lwo)
{
float sinthetai = SinTheta(ref lwi);
float sinthetao = SinTheta(ref lwo);
// Compute cosine term of Oren--Nayar model
float sinphii = SinPhi(ref lwi), cosphii = CosPhi(ref lwi);
float sinphio = SinPhi(ref lwo), cosphio = CosPhi(ref lwo);
float dcos = cosphii*cosphio + sinphii*sinphio;
#if VERBOSE
Assert.IsNotNaN(cosphii,"cosphii "+lwi.ToString());
Assert.IsNotNaN(cosphio, "cosphio " + lwo.ToString());
Assert.IsNotNaN(sinphii, "sinphii " + lwi.ToString());
Assert.IsNotNaN(sinphio, "sinphio " + lwo.ToString());
#endif
float maxcos = Math.Max(0f, dcos);
// Compute sine and tangent terms of Oren--Nayar model
float sinalpha, tanbeta;
if (Math.Abs(CosTheta(ref lwi)) > Math.Abs(CosTheta(ref lwo)))
{
sinalpha = sinthetao;
tanbeta = sinthetai/Math.Abs(CosTheta(ref lwi));
}
else
{
sinalpha = sinthetai;
tanbeta = sinthetao/Math.Abs(CosTheta(ref lwo));
}
fs = R*MathLab.INVPI*
(A + B*maxcos*sinalpha*tanbeta);
#if VERBOSE
if (fs.IsNegative())
{
Tracer.TraceLine("OrenNayar - f - negative");
}
if (fs.IsBlack())
{
Tracer.TraceLine("OrenNayar - f - black");
}
#endif
}