CGAL users discussion list

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

Hi Gert,

Thanks for your complete bug report. It is indeed a bug in Mesh_2. One 
assertion that I added a few months ago was not well thought.

In at line 425 of the file CGAL-4.0.2/include/CGAL/Mesh_2/Refine_edges.h
remove or comment the following lines:

    CGAL_assertion_msg(zone.locate_type != Tr::FACE ||
                       zone.fh == f || zone.fh == n,
                       "Your data set contains at least a vertex that is "
                       "very close to \n"
                       "  a constrained edge! "
                       "Mesh_2 cannot mesh that sort of data set.");

That assertion is wrong, and our set of automatic tests was not able to catch 
that bug. I will think about a proper way to fix the bug.

Le mercredi 25 juillet 2012 02:20:13 gerth a écrit :
> Hi!
> 
> I am new to CGAL and I try to refine some existing triangles such that they
> get filled with a triangular Delauny mesh. I walked through some tutorials
> but ended up with code that seems buggy to me. In some cases it works as
> expected, but as soon as I change some input coordinate values it gives me
> an CGAL::Assertion_exception. The exact error is:
> 
> Unhandled exception at 0x7c812afb in gui.exe: Microsoft C++ exception:
> CGAL::Assertion_exception at memory location 0x0107c438..
> 
> 
> 
> So here is my code:
> 
> //Includes
> #include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
> #include <CGAL/Exact_predicates_exact_constructions_kernel.h>
> #include <CGAL/Cartesian.h>
> #include <CGAL/Delaunay_triangulation_2.h>
> #include <CGAL/Constrained_Delaunay_triangulation_2.h>
> #include <CGAL/Delaunay_mesher_2.h>
> #include <CGAL/Delaunay_mesh_face_base_2.h>
> #include <CGAL/Delaunay_mesh_size_criteria_2.h>
> #include <CGAL/Triangulation_face_base_2.h>
> #include <CGAL/Triangulation_face_base_with_info_2.h>
> #include <CGAL/Polygon_2.h>
> #include <CGAL/Triangulation_2.h>
> #include <CGAL/Vector_3.h>
> #include <CGAL/Triangulation_conformer_2.h>
> #include <CGAL/number_utils.h>
> 
> typedef CGAL::Exact_predicates_inexact_constructions_kernel            K;
> typedef CGAL::Triangulation_vertex_base_2<K>                        Vb;
> typedef CGAL::Delaunay_mesh_face_base_2<K>                    Fb_fine;
> typedef CGAL::Triangulation_data_structure_2<Vb, Fb_fine>
> TDS_fine;
> typedef CGAL::Constrained_Delaunay_triangulation_2<K, TDS_fine>
> CDT_fine;
> typedef CGAL::Delaunay_mesh_size_criteria_2<CDT_fine>
> Criteria_fine;
> typedef CGAL::Delaunay_mesher_2<CDT_fine, Criteria_fine>
> Mesher_fine;
> typedef CDT_fine::Point                                    Point_fine;
> typedef CDT_fine::Vertex_handle
> Vertex_handle_fine;
> typedef CDT_fine::Vertex_iterator
> Vertex_iterator_fine;
> typedef CDT_fine::Triangle                                    Triangle_fine;
> typedef CDT_fine::Vertex                                    Vertex_fine;
> 
> int main()
> {
>     //Fine meshing a triangle
>     //
>     CDT_fine cdt_fine;
>     Vertex_handle_fine v_zero, v_one, v_two;
> 
>     //Define 2d points
>     //
>     double v00 = 0.0;
>     double v01 = 0.0;
> 
>     double v10 = -3.5240345245692879;
>     double v11 = -12.4;  //change this value to -12.429654299747199 and
> everything works fine
> 
>     double v20 = -9.3417057867627591;
>     double v21 = 2.6237986627966166;
> 
> 
>     //Insert 3 points and 3 edges as constraints
>     //
>     v_zero  = cdt_fine.insert( Point_fine(v00, v01 ) );
>     v_one   = cdt_fine.insert( Point_fine(v10, v11 ) );
>     v_two   = cdt_fine.insert( Point_fine(v20, v21 ) );
> 
>     cdt_fine.insert_constraint( v_zero, v_one );
>     cdt_fine.insert_constraint( v_one, v_two );
>     cdt_fine.insert_constraint( v_two, v_zero );
> 
> 
> 
>     //Refine mesh #1
>     //
>     Mesher_fine mesher_fine(cdt_fine);
>     mesher_fine.refine_mesh();    //works
> 
>     //Refine mesh #2
>     //
>     mesher_fine.set_criteria(Criteria_fine(0.125, 1.0));
>     mesher_fine.refine_mesh();    //fails
> 
>     std::cout << "Number of faces: " << cdt_fine.number_of_faces() <<
> std::endl;
>     std::cout << "Number of vertices: " << cdt_fine.number_of_vertices() <<
> std::endl;
> }
> 
> 
> This code gives me an CGAL::Assertion_Exception. If I change the value of
> v11 to a more accurate value like -12.429654299747199, it works fine. What
> is happening here? Is this a bug?
> 
> My environment:
> VS2008 on WinXP (Service Pack 3)
> CGAL 4.0.2
> 
> 
> Hope you can help me. Thank you!
> Gert H.
> 
> 
> 
> --
> View this message in context:
> http://cgal-discuss.949826.n4.nabble.com/Delauny-Mesher-gives-a-CGAL-Assert
> ion-exception-tp4655548.html Sent from the cgal-discuss mailing list archive
> at Nabble.com.

-- 
Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/