Constrained_triangulation_3/ccdt_3_preprocessing.cpp

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
 
#include <CGAL/IO/write_MEDIT.h>
#include <CGAL/Surface_mesh/Surface_mesh.h>
#include <CGAL/Polygon_mesh_processing/self_intersections.h>
#include <CGAL/Polygon_mesh_processing/autorefinement.h>
#include <CGAL/Polygon_mesh_processing/triangulate_faces.h>
#include <CGAL/boost/graph/copy_face_graph.h>
 
#include <CGAL/make_conforming_constrained_Delaunay_triangulation_3.h>
 
#include <CGAL/draw_constrained_triangulation_3.h>
 
using K = CGAL::Exact_predicates_inexact_constructions_kernel;
using Point = K::Point_3;
using Surface_mesh = CGAL::Surface_mesh<Point>;
 
namespace PMP = CGAL::Polygon_mesh_processing;
 
int main(int argc, char* argv[])
{
  const auto filename = (argc > 1) ? argv[1]
                       : CGAL::data_file_path("meshes/mpi_and_sphere.off");
 
  CGAL::Surface_mesh<K::Point_3> mesh;
  if(!CGAL::IO::read_polygon_mesh(filename, mesh)) {
    std::cerr << "Error: cannot read file " << filename << std::endl;
    return EXIT_FAILURE;
  }
 
  std::cout << "Number of facets in " << filename << ": "
            << mesh.number_of_faces() << "\n";
 
  // Check if the mesh is a triangle mesh
  bool triangle_mesh = CGAL::is_triangle_mesh(mesh);
  if(!triangle_mesh)
  {
    std::cout << "Mesh is not a triangle mesh, triangulate faces"
              << " to check self-intersections...\n";
 
    CGAL::Surface_mesh<K::Point_3> trimesh;
    CGAL::copy_face_graph(mesh, trimesh);
    PMP::triangulate_faces(trimesh);
 
    if(PMP::does_self_intersect(trimesh))
    {
      std::cout << "Mesh self-intersects, let's keep the triangulated version"
                << " for future autorefinement\n";
      CGAL::copy_face_graph(trimesh, mesh);
      mesh = std::move(trimesh);
      triangle_mesh = true;
    }
  }
 
  CGAL::Conforming_constrained_Delaunay_triangulation_3<K> ccdt;
  if(triangle_mesh && PMP::does_self_intersect(mesh))
  {
    std::cout << "Mesh is a self-intersecting triangle mesh, perform autorefinement...\n";
 
    // use a polygon soup as container as the output will most likely be non-manifold
    std::vector<K::Point_3> points;
    std::vector<std::vector<std::size_t>> polygons;
    PMP::polygon_mesh_to_polygon_soup(mesh, points, polygons);
    PMP::autorefine_triangle_soup(points, polygons);
    std::cout << "Number of facets after preprocessing: "
              << polygons.size() << "\n";
 
    if(PMP::does_polygon_soup_self_intersect(points, polygons))
    {
      std::cerr << "Error: mesh still self-intersects after autorefine\n";
      return EXIT_FAILURE;
    }
 
    ccdt = CGAL::make_conforming_constrained_Delaunay_triangulation_3(points, polygons);
 
  }
  else
  {
    std::cout << "Number of facets after preprocessing: "
              << mesh.number_of_faces() << "\n";
 
    ccdt = CGAL::make_conforming_constrained_Delaunay_triangulation_3(mesh);
  }
 
  std::cout << "Number of constrained facets in the CDT: "
            << ccdt.number_of_constrained_facets() << '\n';
 
  std::ofstream ofs(argc > 2 ? argv[2] : "out.mesh");
  ofs.precision(17);
  CGAL::IO::write_MEDIT(ofs, ccdt);
 
  CGAL::draw(ccdt);
 
  return EXIT_SUCCESS;
}