Vector3f AreaDiskLight::sample(float u1, float u2, Vector3f &ns) const {
Vector3f p;
UniformSampleDisk(u1, u2, p.x(), p.y());
p.x() *= radius;
p.y() *= radius;
p.z() = height;
ns = lightToWorld.matrix.topLeftCorner<3, 3>() * Vector3f(0.f, 0.f, 1.f);
return lightToWorld * p;
}
//---------------------------------------------------------------------
static Vec3 CosineSampleHemisphere(float u1, float u2) {
Vec3 res;
UniformSampleDisk(u1, u2, res.x, res.y);
res.z = sqrtf(std::max(0.f, 1.f - res.x*res.x - res.y*res.y));
return res;
}