golden_spiral_sampler.hpp

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#pragma once
 
#include "mini_map.hpp"
#include "spherical_voronoi.hpp"
#include "utils_math.hpp"
 
namespace netdem {
 
class GoldenSpiralSampler {
public:
  GoldenSpiralSampler(const GoldenSpiralSampler &) = delete;
 
  GoldenSpiralSampler &operator=(const GoldenSpiralSampler &) = delete;
 
  static GoldenSpiralSampler &GetInstance() {
    static GoldenSpiralSampler instance;
    return instance;
  }
 
  VecXT<Vec3d> Get(int num_samples) {
    VecXT<Vec3d> samples(num_samples);
 
    for (int i = 0; i < num_samples; i++) {
      double theta = std::acos(1.0 - 2.0 * (i + epsilon) /
                                         (num_samples - 1.0 + 2.0 * epsilon));
      double phi = two_pi_by_lambda * i;
      Vec3d vert_sph = {1.0, theta, phi};
      samples[i] = Math::SphericalToCartesian(vert_sph);
    }
 
    return samples;
  }
 
private:
  const double lambda = (1.0 + std::sqrt(5.0)) / 2.0;
  const double two_pi_by_lambda = 2.0 * Math::PI / lambda;
  const double epsilon = 0.36;
 
  GoldenSpiralSampler() {}
};
 
} // namespace netdem