public virtual Spectrum Le(RayDifferential r)
{
return(Spectrum.Create(0.0));
}
public Spectrum Sample_f(
Vector3D woWorld,
out Vector3D wiWorld,
Point2D u,
out double pdf,
out BxdfType sampledType,
BxdfType type = BxdfType.All)
{
// ProfilePhase pp(Prof::BSDFSampling);
// Choose which _BxDF_ to sample
int matchingComps = NumComponents(type);
if (matchingComps == 0)
{
pdf = 0.0;
sampledType = BxdfType.None;
wiWorld = new Vector3D();
return(Spectrum.Create(0.0));
}
int comp = Math.Min(Convert.ToInt32(Math.Floor(u[0] * matchingComps)), matchingComps - 1);
// Get _BxDF_ pointer for chosen component
Bxdf bxdf = null;
int count = comp;
for (int i = 0; i < _nBxDFs; ++i)
{
if (_bxdfs[i].MatchesFlags(type) && count-- == 0)
{
bxdf = _bxdfs[i];
break;
}
}
//CHECK(bxdf != nullptr);
//VLOG(2) << "BSDF::Sample_f chose comp = " << comp << " / matching = " <<
// matchingComps << ", bxdf: " << bxdf->ToString();
// Remap _BxDF_ sample _u_ to $[0,1)^2$
Point2D uRemapped = new Point2D(Math.Min(u[0] * matchingComps - comp, PbrtMath.OneMinusEpsilon),
u[1]);
// Sample chosen _BxDF_
Vector3D wi, wo = WorldToLocal(woWorld);
if (wo.Z == 0)
{
wiWorld = new Vector3D();
pdf = 0.0;
sampledType = BxdfType.None;
return(Spectrum.Create(0.0));
}
pdf = 0.0;
sampledType = bxdf.Type;
Spectrum f = bxdf.Sample_f(wo, out wi, uRemapped, out pdf, out sampledType);
//VLOG(2) << "For wo = " << wo << ", sampled f = " << f << ", pdf = "
// << *pdf << ", ratio = " << ((*pdf > 0) ? (f / *pdf) : Spectrum(0.))
// << ", wi = " << wi;
if (pdf == 0.0)
{
sampledType = BxdfType.None;
wiWorld = new Vector3D();
return(Spectrum.Create(0.0));
}
wiWorld = LocalToWorld(wi);
// Compute overall PDF with all matching _BxDF_s
if ((bxdf.Type & BxdfType.Specular) != BxdfType.Specular && matchingComps > 1)
{
for (int i = 0; i < _nBxDFs; ++i)
{
if (_bxdfs[i] != bxdf && _bxdfs[i].MatchesFlags(type))
{
pdf += _bxdfs[i].Pdf(wo, wi);
}
}
}
if (matchingComps > 1)
{
pdf /= matchingComps;
}
// Compute value of BSDF for sampled direction
if ((bxdf.Type & BxdfType.Specular) != BxdfType.Specular)
{
bool reflect = wiWorld.Dot(_ng) * woWorld.Dot(_ng) > 0.0;
f = Spectrum.Create(0.0);
for (int i = 0; i < _nBxDFs; ++i)
{
if (_bxdfs[i].MatchesFlags(type) &&
((reflect && ((_bxdfs[i].Type & BxdfType.Reflection) == BxdfType.Reflection) ||
(!reflect && ((_bxdfs[i].Type & BxdfType.Transmission) == BxdfType.Transmission)))))
{
f += _bxdfs[i].f(wo, wi);
}
}
}
//VLOG(2) << "Overall f = " << f << ", pdf = " << *pdf << ", ratio = "
// << ((*pdf > 0) ? (f / *pdf) : Spectrum(0.));
return(f);
}