CGAL users discussion list

["Laurent Rineau (CGAL/GeometryFactory)" <>]

Le Monday, May 21, 2018 6:33:00 PM CEST Gabriel Balaban a écrit :

> Dear CGAL people,

>

> I modified the demo mesh_polyhedral complex to make a mesh within a mesh,

> but I seem to be getting holes in the outside mesh for some reason. Could

> you please help me out?

>

> The file holes_in_mesh.png is a screenshot from paraview of the resulting

> mesh,

> and make_mesh.cpp is the c++ program that makes the mesh.

> The outer two files are the inner and outer mesh.

>

> I am aware that for cubes it would be easier to use geometric predicates,

> but I would like to extend the meshing to more complicated meshes so that

> is why my simple test case has surface meshes.

>

> Cheers,

> Gabriel

 

Your construction of the mesh domain is strange: `inner_off` is used twice, with different incidences. If you remove the first occurrence of it, the produced mesh is fine. I attached the modified version I had used.

 

--

Laurent Rineau, PhD

R&D Engineer at GeometryFactory http://www.geometryfactory.com/

Release Manager of the CGAL Project http://www.cgal.org/

 

#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/Polyhedral_complex_mesh_domain_3.h>
#include <CGAL/make_mesh_3.h>

#include <cstdlib>

// Domain
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Mesh_polyhedron_3<K>::type Polyhedron;
typedef CGAL::Polyhedral_complex_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,Mesh_domain::Corner_index,Mesh_domain::Curve_index> C3t3;

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

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

const char* const filenames[] = {
  // "inner_cube.off",
  "inner_cube.off",
  "outer_cube.off"
};

const std::pair<int, int> incident_subdomains[] = {
  // std::make_pair(0, 1),
  std::make_pair(1, 2),
  std::make_pair(0, 2),
};

int main()
{
  const std::size_t nb_patches = sizeof(filenames) / sizeof(const char*);
  CGAL_assertion(sizeof(incident_subdomains) ==
                 nb_patches * sizeof(std::pair<int, int>));
  std::vector<Polyhedron> patches(nb_patches);
  for(std::size_t i = 0; i < nb_patches; ++i) {
    std::ifstream input(filenames[i]);
    if(!(input >> patches[i])) {
      std::cerr << "Error reading " << filenames[i] << " as a polyhedron!\n";
      return EXIT_FAILURE;
    }
  }
  // Create domain
  Mesh_domain domain(patches.begin(), patches.end(),
                     incident_subdomains,
                      incident_subdomains+nb_patches);

  domain.detect_features(); //includes detection of borders

  // Mesh criteria
  // facet_angle = 25,
  // facet_distance = 0.3,
  // cell_radius_edge_ratio = 3,
  // facet_size = 0.3,
  // edge_size = 0.3,

  Mesh_criteria criteria(cell_size = 0.3);

  // Mesh generation
  C3t3 c3t3 = CGAL::make_mesh_3<C3t3>(domain, criteria);

  // Output
  std::ofstream medit_file("out.mesh");
  c3t3.output_to_medit(medit_file);

  return EXIT_SUCCESS;
}