Distinguish inner and boundary vertices of a Mesh_complex_3_in_triangulation_3

vertices.cpp

#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/Labeled_image_mesh_domain_3.h>
#include <CGAL/make_mesh_3.h>
#include <CGAL/Image_3.h>

// Domain
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Labeled_image_mesh_domain_3<CGAL::Image_3,K> Mesh_domain;

// Triangulation
#ifdef CGAL_CONCURRENT_MESH_3
  typedef CGAL::Mesh_triangulation_3<
    Mesh_domain,
    CGAL::Kernel_traits<Mesh_domain>::Kernel, // Same as sequential
    CGAL::Parallel_tag                        // Tag to activate parallelism
  >::type Tr;
#else
  typedef CGAL::Mesh_triangulation_3<Mesh_domain>::type Tr;
#endif
typedef CGAL::Mesh_complex_3_in_triangulation_3<Tr> C3t3;

// Mesh Criteria
typedef CGAL::Mesh_criteria_3<Tr> Mesh_criteria;

// To avoid verbose function and named parameters call
using namespace CGAL::parameters;

int main()
{
  // Domain
  CGAL::Image_3 image;
  image.read("data/liver.inr");
  Mesh_domain domain(image);

  // Mesh criteria
  Mesh_criteria criteria(facet_angle=30, facet_distance=1.2);

  // Mesh generation and optimization in one call
  C3t3 c3t3 = CGAL::make_mesh_3<C3t3>(domain, criteria,
                                      no_perturb(), no_exude());
  
  // Output
  std::ofstream medit_file("out.mesh");
  c3t3.output_to_medit(medit_file);
  
  std::set<Tr::Vertex_handle> boundary_vertices, inner_vertices;

  // A facet is in the complex if it has different indices to its two sides
  // or if its adjacent or opposite cell is not in the complex
  for(C3t3::Facets_in_complex_iterator fit = c3t3.facets_in_complex_begin(), end = c3t3.facets_in_complex_end(); fit != end; ++fit){
    Tr::Cell_handle ch = fit->first;
    int i = fit->second;
    Tr::Cell_handle nh = ch->neighbor(i);
    if(c3t3.is_in_complex(ch) != c3t3.is_in_complex(nh)){
      boundary_vertices.insert(ch->vertex((i+1)% 4));
      boundary_vertices.insert(ch->vertex((i+2)% 4));
      boundary_vertices.insert(ch->vertex((i+3)% 4));
    }
  }
  std::cout << boundary_vertices.size() << " boundary vertices"<< std::endl;

  // A vertex is inside if it is vertex on a cell but not on the boundary
  for (C3t3::Cells_in_complex_iterator cit = c3t3.cells_in_complex_begin(), end = c3t3.cells_in_complex_end(); cit != end; ++cit){
    for(int i=0; i < 4; i++){
      if(boundary_vertices.find(cit->vertex(i)) == boundary_vertices.end()){
        inner_vertices.insert(cit->vertex(i));
      }
    }
  }
  std::cout << inner_vertices.size() << " inner vertices"<< std::endl;

  return 0;
}