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A little bit cheaper triangle random sampling + documentation.

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This commit is contained in:
Vojtech Bubnik 2020-10-15 07:58:13 +02:00
parent cc7eaef493
commit 19a115260a
1 changed files with 17 additions and 4 deletions
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21
src/libslic3r/SLA/SupportPointGenerator.cpp
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@ -357,13 +357,26 @@ std::vector<Vec2f> sample_expolygon(const ExPolygon &expoly, float samples_per_m
double r = random_triangle(rng);
size_t idx_triangle = std::min<size_t>(std::upper_bound(areas.begin(), areas.end(), (float)r) - areas.begin(), areas.size() - 1) * 3;
// Select a random point on the triangle.
double u = float(std::sqrt(random_float(rng)));
double v = float(random_float(rng));
const Vec2f &a = triangles[idx_triangle ++];
const Vec2f &b = triangles[idx_triangle++];
const Vec2f &c = triangles[idx_triangle];
const Vec2f x = a * (1.f - u) + b * (u * (1.f - v)) + c * (v * u);
out.emplace_back(x);
#if 0
// https://www.cs.princeton.edu/~funk/tog02.pdf
// page 814, formula 1.
double u = float(std::sqrt(random_float(rng)));
double v = float(random_float(rng));
out.emplace_back(a * (1.f - u) + b * (u * (1.f - v)) + c * (v * u));
#else
// Greg Turk, Graphics Gems
// https://devsplorer.wordpress.com/2019/08/07/find-a-random-point-on-a-plane-using-barycentric-coordinates-in-unity/
double u = float(random_float(rng));
double v = float(random_float(rng));
if (u + v >= 1.f) {
u = 1.f - u;
v = 1.f - v;
}
out.emplace_back(a + u * (b - a) + v * (c - a));
#endif
}
}
return out;