// sample the bsdf
Colour BSDF::sample(RenderContext *rc,
const HitContext *hc,
const Vec3 &woW,
Vec3 &wiW,
float &pdf,
const float r1,
const float r2,
const float r3,
BxDFtype flags,
BxDFtype *sampled) const
{
// Grab the number of appropriate BxDF
int matchingComps = numComponents(flags);
if (matchingComps == 0)
{
pdf = 0.f;
return Colours::black;
}
// Pick the bxdf
int which = (int)(r3 * matchingComps);//rc->rnd.randInt(matchingComps - 1);
which = which == matchingComps ? matchingComps - 1 : which;
BxDF *bxdf = NULL;
int count = which;
int bxdfNum = 0;
for (int i = 0; i < numBxDFs; ++i)
{
if (bxdfs[i]->hasFlags(flags))
{
if (count-- == 0)
{
bxdf = bxdfs[i];
bxdfNum = i;
break;
}
}
}
// Sample the appropriate BxDF
pdf = 0.0f;
Vec3 wi;
const Vec3 wo = hc->onb.untransform(woW);
const Colour C = getCol(rc, hc, bxdfNum);
Colour f = bxdf->sample(rc, wo, wi, pdf, r1, r2, C);
f = adjust(hc, f, bxdfNum, wo, wi); // custom adjustment for each BSDF
if (pdf == 0.0f) return 0.0f;
if (sampled != NULL) *sampled = bxdf->type;
wiW = hc->onb.transform(wi);
// Compute overall PDF with all matching BxDFs
if (matchingComps > 1)
{
if (!(bxdf->type & BSDF_SPECULAR))
{
for (int i = 0; i < numBxDFs; ++i)
{
if (bxdfs[i] != bxdf && bxdfs[i]->hasFlags(flags))
pdf += bxdfs[i]->pdf(wo, wi);
}
}
pdf /= matchingComps;
}
// Compute value of BSDF for sampled direction
if (!(bxdf->type & BSDF_SPECULAR))
{
f = 0.0;
if (Dot(wiW, hc->gNormal) * Dot(woW, hc->gNormal) > 0)
flags = BxDFtype(flags & ~BSDF_TRANSMISSION); // ignore BTDFs
else
flags = BxDFtype(flags & ~BSDF_REFLECTION); // ignore BRDFs
for (int i = 0; i < numBxDFs; ++i)
{
if (bxdfs[i]->hasFlags(flags))
{
// Tweak eval output to suit each BSDF
f += adjust(hc, bxdfs[i]->eval(wo, wi, getCol(rc, hc, bxdfNum)), i, wo, wi);
}
}
}
return f;
}
