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Uniform distribution of cos(theta) in SphericalIndependent

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cpf 2022-05-06 10:19:16 +02:00
parent ec0b9bbd01
commit 806367c124
1 changed files with 7 additions and 3 deletions
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10
src/distribution_spatial.cpp
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@ -172,10 +172,14 @@ Position SphericalIndependent::sample(uint64_t* seed) const
{
double r = r_->sample(seed);
double theta = theta_->sample(seed);
// To distribute the points uniformly in the sphere, we must ensure that
// cos(theta) and not theta is uniformly distributed.
// This is done with theta_cos.
double theta_cos = std::acos((theta / (0.5 * PI)) - 1);
double phi = phi_->sample(seed);
double x = r * sin(theta) * cos(phi) + origin_.x;
double y = r * sin(theta) * sin(phi) + origin_.y;
double z = r * cos(theta) + origin_.z;
double x = r * sin(theta_cos) * cos(phi) + origin_.x;
double y = r * sin(theta_cos) * sin(phi) + origin_.y;
double z = r * cos(theta_cos) + origin_.z;
return {x, y, z};
}