Polygon_mesh_processing/volume_connected_components.cpp

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Surface_mesh.h>
 
#include <CGAL/Polygon_mesh_processing/orientation.h>
#include <CGAL/Polygon_mesh_processing/IO/polygon_mesh_io.h>
 
#include <CGAL/boost/graph/Face_filtered_graph.h>
 
#include <fstream>
#include <iostream>
#include <sstream>
#include <string>
 
typedef CGAL::Exact_predicates_inexact_constructions_kernel   Kernel;
typedef CGAL::Surface_mesh<Kernel::Point_3>                   Mesh;
 
namespace PMP = CGAL::Polygon_mesh_processing;
namespace params = CGAL::parameters;
 
int main(int argc, char** argv)
{
  const std::string filename = (argc > 1) ? argv[1] : CGAL::data_file_path("meshes/blobby.off");
 
  Mesh mesh;
  if(!PMP::IO::read_polygon_mesh(filename, mesh))
  {
    std::cerr << "Invalid input." << std::endl;
    return 1;
  }
 
  // property map to assign a volume id for each face
  Mesh::Property_map<Mesh::Face_index, std::size_t> vol_id_map =
    mesh.add_property_map<Mesh::Face_index, std::size_t>().first;
 
  // fill the volume id map
  std::vector<PMP::Volume_error_code> err_codes;
  std::size_t nb_vol = PMP::volume_connected_components(mesh, vol_id_map,
                                                        params::error_codes(std::ref(err_codes)));
  std::cout << "Found " << nb_vol << " volumes\n";
 
  // write each volume in an OFF file
  typedef CGAL::Face_filtered_graph<Mesh> Filtered_graph;
  Filtered_graph vol_mesh(mesh, 0, vol_id_map);
  for(std::size_t id = 0; id < nb_vol; ++id)
  {
    if(err_codes[id] != PMP::VALID_VOLUME)
      std::cerr << "There is an issue with volume #" << id << "\n";
 
    if(id > 0)
      vol_mesh.set_selected_faces(id, vol_id_map);
 
    Mesh out;
    CGAL::copy_face_graph(vol_mesh, out);
    std::ostringstream oss;
    oss << "vol_" << id <<".off";
    std::ofstream os(oss.str().data());
    os << out;
  }
  return 0;
}