Constrained_triangulation_3/ccdt_3_check_preconditions.cpp

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
 
#include <CGAL/Surface_mesh/Surface_mesh.h>
#include <CGAL/Polygon_mesh_processing/triangulate_faces.h>
#include <CGAL/Polygon_mesh_processing/self_intersections.h>
#include <CGAL/boost/graph/copy_face_graph.h>
#include <CGAL/Polygon_mesh_processing/polygon_mesh_to_polygon_soup.h>
 
#include <CGAL/make_conforming_constrained_Delaunay_triangulation_3.h>
 
#include <CGAL/draw_constrained_triangulation_3.h>
#include <CGAL/IO/polygon_mesh_io.h>
#include <CGAL/IO/polygon_soup_io.h>
#include <CGAL/IO/write_MEDIT.h>
 
#include <vector>
 
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;
 
// Function to verify preconditions for a mesh input
bool verify_preconditions_mesh(const Surface_mesh& mesh)
{
  if(CGAL::is_triangle_mesh(mesh))
    return !CGAL::Polygon_mesh_processing::does_self_intersect(mesh);
 
  Surface_mesh triangle_mesh;
  CGAL::copy_face_graph(mesh, triangle_mesh);
  bool tri_ok = CGAL::Polygon_mesh_processing::triangulate_faces(triangle_mesh);
  if(!tri_ok)
    return false;
 
  return !CGAL::Polygon_mesh_processing::does_self_intersect(triangle_mesh);
}
 
// Function to verify preconditions for a polygon soup input
template <typename PointRange, typename PolygonRange>
bool verify_preconditions_soup(const PointRange& points, const PolygonRange& polygons)
{
  return !CGAL::Polygon_mesh_processing::does_polygon_soup_self_intersect(points, polygons);
}
 
int main(int argc, char* argv[])
{
  const auto filename = (argc > 1) ? argv[1]
                       : CGAL::data_file_path("meshes/cubes.off");
 
  // Read polygon soup
  using Points = std::vector<Point>;
  using PLC_face = std::vector<std::size_t>;
  using PLC_faces = std::vector<PLC_face>;
  Points points;
  PLC_faces faces;
  if(!CGAL::IO::read_polygon_soup(filename, points, faces))
  {
    std::cerr << "Error: cannot read file " << filename << std::endl;
    return EXIT_FAILURE;
  }
 
  // When possible, convert polygon soup to polygon mesh
  CGAL::Surface_mesh<K::Point_3> mesh;
  if(CGAL::Polygon_mesh_processing::is_polygon_soup_a_polygon_mesh(faces))
  {
    CGAL::Polygon_mesh_processing::polygon_soup_to_polygon_mesh(points, faces, mesh);
    std::cout << "Number of facets in " << filename << ": " << mesh.number_of_faces() << "\n";
  }
 
  // Verify preconditions for the mesh input
  const bool is_polygon_mesh = !mesh.is_empty();
  if(is_polygon_mesh && !verify_preconditions_mesh(mesh))
  {
    std::cerr << "Error: input mesh is not a valid input for CCDT_3\n";
    return EXIT_FAILURE;
  }
  else if(!verify_preconditions_soup(points, faces))
  {
    std::cerr << "Error: input polygon soup is not a valid input for CCDT_3\n";
    return EXIT_FAILURE;
  }
 
  // Build conforming constrained Delaunay triangulation
  auto ccdt = is_polygon_mesh
    ? CGAL::make_conforming_constrained_Delaunay_triangulation_3(mesh)
    : CGAL::make_conforming_constrained_Delaunay_triangulation_3(points, faces);
 
  // Print mesh details
  if(ccdt.number_of_constrained_facets() == 0)
  {
    std::cerr << "Error: no constrained facets in the CDT.\n";
    std::cerr << "Invalid input.\n";
    return EXIT_SUCCESS;
  }
 
  std::cout << "Number of constrained facets in the CDT: "
            << ccdt.number_of_constrained_facets() << '\n';
 
  // Output
  std::ofstream ofs(argc > 2 ? argv[2] : "out.mesh");
  ofs.precision(17);
  CGAL::IO::write_MEDIT(ofs, ccdt);
 
  CGAL::draw(ccdt);
 
  return EXIT_SUCCESS;
}