CGAL users discussion list

[Gert Hutter <>]

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.