Point Triangle::Sample(float u1, float u2, Normal *Ns) const {
float b1, b2;
UniformSampleTriangle(u1, u2, &b1, &b2);
// Get triangle vertices in _p1_, _p2_, and _p3_
const Point &p1 = mesh->p[v[0]];
const Point &p2 = mesh->p[v[1]];
const Point &p3 = mesh->p[v[2]];
Point p = b1 * p1 + b2 * p2 + (1.f - b1 - b2) * p3;
Normal n = Normal(Cross(p2-p1, p3-p1));
*Ns = Normalize(n);
if (ReverseOrientation) *Ns *= -1.f;
return p;
}
Interaction Triangle::Sample(const Point2f &u) const {
Point2f b = UniformSampleTriangle(u);
// Get triangle vertices in _p0_, _p1_, and _p2_
const Point3f &p0 = mesh->p[v[0]];
const Point3f &p1 = mesh->p[v[1]];
const Point3f &p2 = mesh->p[v[2]];
Interaction it;
it.p = b[0] * p0 + b[1] * p1 + (1 - b[0] - b[1]) * p2;
// Compute surface normal for sampled point on triangle
if (mesh->n)
it.n = Normalize(b[0] * mesh->n[v[0]] + b[1] * mesh->n[v[1]] +
(1 - b[0] - b[1]) * mesh->n[v[2]]);
else
it.n = Normalize(Normal3f(Cross(p1 - p0, p2 - p0)));
if (reverseOrientation) it.n *= -1;
// Compute error bounds for sampled point on triangle
Point3f pAbsSum =
Abs(b[0] * p0) + Abs(b[1] * p1) + Abs((1 - b[0] - b[1]) * p2);
it.pError = gamma(6) * Vector3f(pAbsSum.x, pAbsSum.y, pAbsSum.z);
return it;
}