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)
{
double a = 1 - ((roughness2 / 2 * (roughness2 + 0.33)));
double b = 0.45 * roughness2 / (roughness2 + 0.09);
double sinThetaI = Utils.SinTheta(wi);
double sinThetaO = Utils.SinTheta(wo);
double sinAlpha;
double tanBeta;
if (Utils.AbsCosTheta(wi) > Utils.AbsCosTheta(wo))
{
sinAlpha = sinThetaO;
tanBeta = sinThetaI / Utils.AbsCosTheta(wi);
}
else
{
sinAlpha = sinThetaI;
tanBeta = sinThetaO / Utils.AbsCosTheta(wo);
}
double maxCos = 0;
if (sinThetaI > 1e-4 && sinThetaO > 1e-4)
{
double dCos = Utils.CosPhi(wi) * Utils.CosPhi(wo) + Utils.SinPhi(wi) * Utils.SinPhi(wo);
maxCos = Math.Max(0, dCos);
}
Spectrum nnn = (kd / Math.PI) * (a + b * maxCos * sinAlpha * tanBeta);
return(nnn);
}
public override Spectrum f(Vector3 wo, Vector3 wi)
{
Vector3 wh = wo + wi;
if (wh.z < 0.0)
{
wi = -wi;
wh = -wh;
}
if (wh.LengthSquared() == 0.0) // epsilon ?
{
return(Spectrum.ZeroSpectrum);
}
wh = wh.Normalize();
double cos_phi_h = Utils.CosPhi(wh);
double sin_phi_h = Utils.SinPhi(wh);
double cos_theta_h = Utils.CosTheta(wh);
double sin_theta_h = Utils.SinTheta(wh);
Vector3 w_hx = new Vector3(cos_phi_h * cos_theta_h, sin_phi_h * cos_theta_h, -sin_theta_h);
Vector3 w_hy = new Vector3(-sin_phi_h, cos_phi_h, 0.0);
Vector3 w_d = new Vector3(Vector3.Dot(wi, w_hx), Vector3.Dot(wi, w_hy), Vector3.Dot(wi, wh));
double theta_h = SphericalTheta(wh);
double theta_d = SphericalTheta(w_d);
double phi_d = SphericalPhi(w_d);
if (phi_d > Math.PI)
{
phi_d = phi_d - Math.PI;
}
// Get i.
int theta_h_idx = ThetaHalfIndex(theta_h);
int theta_d_idx = ThetaDiffIndex(theta_d);
int phi_d_idx = PhiDiffIndex(phi_d);
int i = phi_d_idx + (BRDF_SAMPLING_RES_PHI_D / 2) * (theta_d_idx + theta_h_idx * BRDF_SAMPLING_RES_THETA_D);
return(Spectrum.Create(Vector <double> .Build.Dense(new[] { brdf[3 * i], brdf[3 * i + 1], brdf[3 * i + 2] })));
}
public override Spectrum f(Vector3 wo, Vector3 wi)
{
// var phiWi = Phi(wi.x, wi.y);
// var phiWo = Phi(wo.x, wo.y);
// var thetaWi = Theta(wi.x, wi.y, wi.z);
// var thetaWo = Theta(wo.x, wo.y, wo.z);
//
// var alpha = Math.Max(thetaWi, thetaWo);
// var beta = Math.Min(thetaWi, thetaWo);
//
// return kd * Utils.PiInv * (a + b * Math.Max(0, Math.Cos(phiWi - phiWo))) * Math.Sin(alpha) * Math.Tan(beta);
var sinThetaI = Utils.SinTheta(wi);
var sinThetaO = Utils.SinTheta(wo);
var maxCos = 0.0;
if (sinThetaI > 1e-4 && sinThetaO > 1e-4)
{
var sinPhiI = Utils.SinPhi(wi);
var cosPhiI = Utils.CosPhi(wi);
var sinPhiO = Utils.SinPhi(wo);
var cosPhiO = Utils.CosPhi(wo);
var dCos = cosPhiI * cosPhiO + sinPhiI * sinPhiO;
maxCos = Math.Max(0, dCos);
}
double sinAlpha;
double tanBeta;
if (Utils.AbsCosTheta(wi) > Utils.AbsCosTheta(wo))
{
sinAlpha = sinThetaO;
tanBeta = sinThetaI / Utils.AbsCosTheta(wi);
}
else
{
sinAlpha = sinThetaI;
tanBeta = sinThetaO / Utils.AbsCosTheta(wo);
}
return(kd * Utils.PiInv * (a + b * maxCos * sinAlpha * tanBeta));
}