void SampleFromSurface()

in src/PreprocessMesh.cpp [23:85]

• 49 lines of code
• 8 McCabe index (conditional complexity)

void SampleFromSurface(
    pangolin::Geometry& geom,
    std::vector<Eigen::Vector3f>& surfpts,
    int num_sample) {
  float total_area = 0.0f;

  std::vector<float> cdf_by_area;

  std::vector<Eigen::Vector3i> linearized_faces;

  for (const auto& object : geom.objects) {
    auto it_vert_indices = object.second.attributes.find("vertex_indices");
    if (it_vert_indices != object.second.attributes.end()) {
      pangolin::Image<uint32_t> ibo =
          pangolin::get<pangolin::Image<uint32_t>>(it_vert_indices->second);

      for (int i = 0; i < ibo.h; ++i) {
        linearized_faces.emplace_back(ibo(0, i), ibo(1, i), ibo(2, i));
      }
    }
  }

  pangolin::Image<float> vertices =
      pangolin::get<pangolin::Image<float>>(geom.buffers["geometry"].attributes["vertex"]);

  for (const Eigen::Vector3i& face : linearized_faces) {
    float area = TriangleArea(
        (Eigen::Vector3f)Eigen::Map<Eigen::Vector3f>(vertices.RowPtr(face(0))),
        (Eigen::Vector3f)Eigen::Map<Eigen::Vector3f>(vertices.RowPtr(face(1))),
        (Eigen::Vector3f)Eigen::Map<Eigen::Vector3f>(vertices.RowPtr(face(2))));

    if (std::isnan(area)) {
      area = 0.f;
    }

    total_area += area;

    if (cdf_by_area.empty()) {
      cdf_by_area.push_back(area);

    } else {
      cdf_by_area.push_back(cdf_by_area.back() + area);
    }
  }

  std::random_device seeder;
  std::mt19937 generator(seeder());
  std::uniform_real_distribution<float> rand_dist(0.0, total_area);

  while ((int)surfpts.size() < num_sample) {
    float tri_sample = rand_dist(generator);
    std::vector<float>::iterator tri_index_iter =
        lower_bound(cdf_by_area.begin(), cdf_by_area.end(), tri_sample);
    int tri_index = tri_index_iter - cdf_by_area.begin();

    const Eigen::Vector3i& face = linearized_faces[tri_index];

    surfpts.push_back(SamplePointFromTriangle(
        Eigen::Map<Eigen::Vector3f>(vertices.RowPtr(face(0))),
        Eigen::Map<Eigen::Vector3f>(vertices.RowPtr(face(1))),
        Eigen::Map<Eigen::Vector3f>(vertices.RowPtr(face(2)))));
  }
}