bool Cube::sampleDirection(PathSampleGenerator &sampler, const PositionSample &point, DirectionSample &sample) const
{
Vec3f d = SampleWarp::cosineHemisphere(sampler.next2D());
sample.d = TangentFrame(point.Ng).toGlobal(d);
sample.weight = Vec3f(1.0f);
sample.pdf = SampleWarp::cosineHemispherePdf(d);
return true;
}
void Primitive::setupTangentFrame(const IntersectionTemporary &data,
const IntersectionInfo &info, TangentFrame &dst) const
{
const Texture *bump = info.bsdf ? info.bsdf->bump().get() : nullptr;
if ((!bump || bump->isConstant()) && !info.bsdf->lobes().isAnisotropic()) {
dst = TangentFrame(info.Ns);
return;
}
Vec3f T, B, N(info.Ns);
if (!tangentSpace(data, info, T, B)) {
dst = TangentFrame(info.Ns);
return;
}
if (bump && !bump->isConstant()) {
Vec2f dudv;
bump->derivatives(info.uv, dudv);
T += info.Ns*(dudv.x() - info.Ns.dot(T));
B += info.Ns*(dudv.y() - info.Ns.dot(B));
N = T.cross(B);
if (N == 0.0f) {
dst = TangentFrame(info.Ns);
return;
}
if (N.dot(info.Ns) < 0.0f)
N = -N;
N.normalize();
}
T = (T - N.dot(T)*N);
if (T == 0.0f) {
dst = TangentFrame(info.Ns);
return;
}
T.normalize();
B = N.cross(T);
dst = TangentFrame(N, T, B);
}
void Quad::prepareForRender()
{
_base = _transform*Vec3f(0.0f);
_edge0 = _transform.transformVector(Vec3f(1.0f, 0.0f, 0.0f));
_edge1 = _transform.transformVector(Vec3f(0.0f, 0.0f, 1.0f));
_base -= _edge0*0.5f;
_base -= _edge1*0.5f;
Vec3f n = _edge1.cross(_edge0);
_area = n.length();
_invArea = 1.0f/_area;
n /= _area;
_frame = TangentFrame(n, _edge0.normalized(), _edge1.normalized());
_invUvSq = 1.0f/Vec2f(_edge0.lengthSq(), _edge1.lengthSq());
Primitive::prepareForRender();
}
bool HenyeyGreensteinPhaseFunction::sample(PathSampleGenerator &sampler, const Vec3f &wi, PhaseSample &sample) const
{
Vec2f xi = sampler.next2D(MediumPhaseSample);
if (_g == 0.0f) {
sample.w = SampleWarp::uniformSphere(xi);
sample.weight = Vec3f(1.0f);
sample.pdf = SampleWarp::uniformSpherePdf();
} else {
float phi = xi.x()*TWO_PI;
float cosTheta = (1.0f + _g*_g - sqr((1.0f - _g*_g)/(1.0f + _g*(xi.y()*2.0f - 1.0f))))/(2.0f*_g);
float sinTheta = std::sqrt(max(1.0f - cosTheta*cosTheta, 0.0f));
sample.w = TangentFrame(wi).toGlobal(Vec3f(
std::cos(phi)*sinTheta,
std::sin(phi)*sinTheta,
cosTheta
));
sample.weight = Vec3f(1.0f);
sample.pdf = henyeyGreenstein(cosTheta);
}
return true;
}
