conversion between surface mesh and nef_polyhedron_3

[Supranaturaler]

Issue Details

I can construct nef_polyhedron_3 using unclosed surface mesh. But when I convert this nef_polyhedron_3 to surface mesh, I got empty result. How can I get the original surface mesh using nef_polyhedron_3?

Source Code

#include "CGAL/Exact_predicates_exact_constructions_kernel.h"
typedef CGAL::Exact_predicates_exact_constructions_kernel Kernel;
typedef Kernel::Point_3 Point_3;

#include "CGAL/Surface_mesh.h"
typedef CGAL::Surface_mesh<Point_3> SurfaceMesh;

#include "CGAL/Nef_polyhedron_3.h"
typedef CGAL::Nef_polyhedron_3<Kernel> NefPolyhedron;

#include "CGAL/boost/graph/convert_nef_polyhedron_to_polygon_mesh.h"

int main(int argc, char* argv[])
{
    SurfaceMesh surfaceMesh;
    SurfaceMesh::Vertex_index v0 = surfaceMesh.add_vertex(Point_3(-1, 0, 0));
    SurfaceMesh::Vertex_index v1 = surfaceMesh.add_vertex(Point_3(1, 0, 0));
    SurfaceMesh::Vertex_index v2 = surfaceMesh.add_vertex(Point_3(0, 1, 0));
    surfaceMesh.add_face(v0, v1, v2);
    std::cout << "Before conversion, number_of_faces: " << surfaceMesh.number_of_faces() << std::endl;

    NefPolyhedron nefPoly(surfaceMesh);
    std::cout << "NefPolyhedron, number_of_faces: " << nefPoly.number_of_facets() << std::endl;

    SurfaceMesh convertedSurfaceMesh;
    CGAL::convert_nef_polyhedron_to_polygon_mesh(nefPoly, convertedSurfaceMesh, true);
    std::cout << "After conversion, number_of_faces: " << convertedSurfaceMesh.number_of_faces() << std::endl;

    return EXIT_SUCCESS;
}

Environment

• Operating system (Windows/Mac/Linux, 32/64 bits): Windows 64 bits
• Compiler: MSVC-2019-Community
• Release or debug mode: debug
• Specific flags used (if any):
• CGAL version: CGAL-5.4
• Boost version: boost_1_76_0
• Other libraries versions if used (Eigen, TBB, etc.):

[stla]

Hello,

A polyhedron is closed by definition, and a 3D triangle is not closed. Maybe it is the reason?