Surface_mesh_segmentation/extract_segmentation_into_mesh_example.cpp

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Surface_mesh.h>
 
#include <CGAL/boost/graph/copy_face_graph.h>
#include <CGAL/boost/graph/Face_filtered_graph.h>
#include <CGAL/Polygon_mesh_processing/measure.h>
#include <CGAL/Polygon_mesh_processing/IO/polygon_mesh_io.h>
#include <CGAL/mesh_segmentation.h>
 
#include <iostream>
#include <fstream>
#include <sstream>
 
typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
typedef CGAL::Surface_mesh<Kernel::Point_3> SM;
typedef boost::graph_traits<SM>::face_descriptor face_descriptor;
 
int main(int argc, char** argv )
{
  const std::string filename = (argc > 1) ? argv[1] : CGAL::data_file_path("meshes/cactus.off");
 
  SM mesh;
  if(!CGAL::Polygon_mesh_processing::IO::read_polygon_mesh(filename, mesh) ||
     !CGAL::is_triangle_mesh(mesh))
  {
    std::cerr << "Invalid input file." << std::endl;
    return EXIT_FAILURE;
  }
 
  typedef SM::Property_map<face_descriptor,double> Facet_double_map;
  Facet_double_map sdf_property_map;
 
  sdf_property_map = mesh.add_property_map<face_descriptor,double>("f:sdf").first;
 
  CGAL::sdf_values(mesh, sdf_property_map);
 
  // create a property-map for segment-ids
  typedef SM::Property_map<face_descriptor, std::size_t> Facet_int_map;
  Facet_int_map segment_property_map = mesh.add_property_map<face_descriptor,std::size_t>("f:sid").first;;
 
  // segment the mesh using default parameters for number of levels, and smoothing lambda
  // Any other scalar values can be used instead of using SDF values computed using the CGAL function
  std::size_t number_of_segments = CGAL::segmentation_from_sdf_values(mesh, sdf_property_map, segment_property_map);
 
  typedef CGAL::Face_filtered_graph<SM> Filtered_graph;
  //print area of each segment and then put it in a Mesh and print it in an OFF file
  Filtered_graph segment_mesh(mesh);
  for(std::size_t id = 0; id < number_of_segments; ++id)
  {
    segment_mesh.set_selected_faces(id, segment_property_map);
    std::cout << "Segment "<<id<<"'s area is : "<<CGAL::Polygon_mesh_processing::area(segment_mesh)<<std::endl;
 
    SM out;
    CGAL::copy_face_graph(segment_mesh, out);
    std::ostringstream oss;
    oss << "Segment_" << id<<".off";
    std::ofstream os(oss.str().data());
    os<<out;
  }
}