public override Spectrum f(Vector3 wo, Vector3 wi)
{
if (!Utils.SameHemisphere(wo, wi))
{
return(Spectrum.ZeroSpectrum);
}
// Cos term
// Adicijski izrek: cos(x +- y) = cos(x) * cos(y) -+ sin(x) * sin(y)
double cosDiff = Utils.CosPhi(wi) * Utils.CosPhi(wo) + Utils.SinPhi(wi) * Utils.SinPhi(wo);
// Sin and tan terms
double sinAlpha, tanBeta;
if (Utils.AbsCosTheta(wi) > Utils.AbsCosTheta(wo)) // oTheta > iTheta
{
sinAlpha = Utils.SinTheta(wo);
tanBeta = Utils.SinTheta(wi) / Utils.AbsCosTheta(wi);
}
else // iTheta >= oTheta
{
sinAlpha = Utils.SinTheta(wi);
tanBeta = Utils.SinTheta(wo) / Utils.AbsCosTheta(wo);
}
return(kd * Utils.PiInv * (A + B * Math.Max(0, cosDiff) * sinAlpha * tanBeta));
}
public override Spectrum f(Vector3 wo, Vector3 wi)
{
if (!Utils.SameHemisphere(wo, wi))
{
return(Spectrum.ZeroSpectrum);
}
double A = 1 - (this.cov) / (2 * (this.cov + 0.33));
double B = 0.45 * (this.cov) / (this.cov + 0.09);
double r_o = Math.Sqrt(wo.x * wo.x + wo.y * wo.y + wo.z * wo.z);
double r_i = Math.Sqrt(wi.x * wi.x + wi.y * wi.y + wi.z * wi.z);
//double alpha = Math.Max(Math.Acos(wo.z / r_o), Math.Acos(wi.z / r_i));
//double beta = Math.Min(Math.Acos(wo.z / r_o), Math.Acos(wi.z / r_i));
//double cosPhi_o = Utils.CosPhi(wo);
//double cosPhi_i = Utils.CosPhi(wi);
//double cosTheta_o = Utils.CosTheta(wo);
//double cosTheta_i = Utils.CosTheta(wi);
double alpha = Math.Max(Math.Acos(wo.z / r_o), Math.Acos(wi.z / r_i));
double beta = Math.Min(Math.Acos(wo.z / r_o), Math.Acos(wi.z / r_i));
double phi_o = Math.Atan(wo.y / wo.x);
double phi_i = Math.Atan(wi.y / wo.x);
return(kd * Utils.PiInv * (A + B * Math.Max(0, Math.Cos(phi_i - phi_o)) * Math.Sin(alpha) * Math.Tan(beta)));
}
public override Spectrum f(Vector3 wo, Vector3 wi)
{
if (!Utils.SameHemisphere(wo, wi))
{
return(Spectrum.ZeroSpectrum);
}
return(kd * Utils.PiInv);
}
public override double Pdf(Vector3 wo, Vector3 wi)
{
if (!Utils.SameHemisphere(wo, wi))
{
return(0.0);
}
return(Math.Abs(wi.z) * Utils.PiInv);
}
public static double CosineHemispherePdf(Vector3 wo, Vector3 wi)
{
if (!Utils.SameHemisphere(wo, wi))
{
return(0);
}
return(Math.Abs(wi.z) * Utils.PiInv);
}