Mesh_3/mesh_3D_image_with_image_initialization.cpp

#include "random_labeled_image.h"
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
 
#include <CGAL/Mesh_triangulation_3.h>
#include <CGAL/Mesh_complex_3_in_triangulation_3.h>
#include <CGAL/Mesh_criteria_3.h>
 
#include <CGAL/Mesh_3/Construct_initial_points_labeled_image.h>
 
#include <CGAL/Labeled_mesh_domain_3.h>
#include <CGAL/make_mesh_3.h>
#include <CGAL/Image_3.h>
 
#include <CGAL/IO/File_medit.h>
 
#include <cstdlib>
 
 
// Domain
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Labeled_mesh_domain_3<K> Mesh_domain;
 
#ifdef CGAL_CONCURRENT_MESH_3
typedef CGAL::Parallel_tag Concurrency_tag;
#else
typedef CGAL::Sequential_tag Concurrency_tag;
#endif
 
// Triangulation
typedef CGAL::Mesh_triangulation_3<Mesh_domain,CGAL::Default,Concurrency_tag>::type Tr;
 
typedef CGAL::Mesh_complex_3_in_triangulation_3<Tr> C3t3;
 
// Criteria
typedef CGAL::Mesh_criteria_3<Tr> Mesh_criteria;
 
namespace params = CGAL::parameters;
 
constexpr int number_of_spheres = 50;
 
int main()
{
  CGAL::Image_3 image = random_labeled_image(number_of_spheres);
 
  // Domain
  Mesh_domain domain = Mesh_domain::create_labeled_image_mesh_domain(image);
 
  // Mesh criteria
  Mesh_criteria criteria(params::facet_angle(30).facet_size(3).facet_distance(1)
                         .cell_radius_edge_ratio(3).cell_size(3));
 
  // Mesh generation with a custom initialization that places points
  // on the surface of each connected component of the image.
  CGAL::Construct_initial_points_labeled_image<C3t3, Mesh_domain>
      img_pts_generator(image, domain, CGAL::parameters::verbose(true));
 
  C3t3 c3t3 = CGAL::make_mesh_3<C3t3>(domain, criteria,
                                      params::initial_points_generator(img_pts_generator));
  const auto& tr = c3t3.triangulation();
 
  // Output
  std::ofstream medit_file("out.mesh");
  CGAL::IO::write_MEDIT(medit_file, c3t3);
  medit_file.close();
 
  std::set<int> subdomains;
  for(const auto& c : tr.finite_cell_handles()) {
    if(c3t3.is_in_complex(c))
      subdomains.insert(c3t3.subdomain_index(c));
  }
  if(subdomains.size() == number_of_spheres) {
    std::cout << "Success: " << subdomains.size()
              << " subdomains were meshed." << std::endl;
    return EXIT_SUCCESS;
  } else {
    std::cerr << "Failure: " << subdomains.size()
              << " subdomains were meshed. Expected " << number_of_spheres << " instead.\n";
    return EXIT_FAILURE;
  }
}