CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Joe C wrote:
> someone from CGAL can help on this thread? The old thread has been there 
> for more than two years still waiting for an answer.
I do not now this package. However I add a look yesterday. I understood
why this does crash but finding why would have took me a lot of time ( 
that I don't have right now).
If you can simply your models to come with smaller size examples
it will be easier to find out what is going on.

S.

> On Wed, Oct 27, 2010 at 3:50 PM, Joe C < 
> <mailto:>> wrote:
>
>     Hi,
>
>     I am getting crash while performing 3D difference. When I searched
>     for the forum, I found this old thread which I copied below. It
>     seems that this issue still exists (I'm using fairly recent release
>     CGAL 3.6.1). Any solution to this?
>
>     Joe
>
>
>     *****************************************************************
>     The following is the contents from the old thread:
>
>
>
>     Hi there,
>
>      
>
>     I have encountered a crash during execution of boolean operations on
>     a data set.  The assertion is below.
>
>      
>
>     CGAL error: assertion violation!
>
>     Expr: itl != it->second.end()
>
>     File: $(CGALROOT)\include\CGAL/Nef_3/SNC_external
>
>     _structure.h
>
>     Line: 567
>
>      
>
>     If the assertion is ignored, a null-pointer reference occurs in
>     make_twins() a few lines below that code.  I have attached the
>     offending files, and a modification of the example
>     “interface_polyhedron” program that demonstrates this error.  The
>     kernels I have used are Cartesian<Gmpq> and
>     Exact_predicates_exact_constructions_kernel.  I know the input files
>     are ugly (a.off is pretty ugly), but they pass is_valid() and
>     is_closed()/is_simple() tests both in Polyhedron_3 and Nef_polyhedron_3.
>
>      
>
>     If anyone can provide any more details regarding how to avoid this
>     kind of error, or why this is happening, I am glad to hear it!
>
>      
>
>     Thanks,
>
>      
>
>     Stephen
>
>     //#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
>     #include <CGAL/Gmpq.h>
>     #include <CGAL/Cartesian.h>
>     #include <CGAL/Polyhedron_3.h>
>     #include <CGAL/IO/Polyhedron_iostream.h>
>     #include <CGAL/Nef_polyhedron_3.h>
>     #include <CGAL/IO/Nef_polyhedron_iostream_3.h>
>     #include <iostream>
>     #include <fstream>
>
>     typedef CGAL::Cartesian<CGAL::Gmpq> Kernel;
>     typedef CGAL::Polyhedron_3<Kernel> Polyhedron;
>     typedef CGAL::Nef_polyhedron_3<Kernel> Nef_polyhedron;
>     typedef Kernel::Vector_3 Vector_3;
>     typedef Kernel::Aff_transformation_3 Aff_transformation_3;
>
>     Polyhedron* loadPolyFromFile( const char* file )
>     {
>     std::ifstream fin( file ) ;
>     if ( !fin.is_open() ) return NULL ;
>
>     Polyhedron* p = new Polyhedron() ;
>     fin >> *p ;
>
>     if ( p->is_closed() && p->is_valid() )
>     {
>     // Only return when closed and valid.
>     return p ;
>     }
>     else
>     {
>     delete p ;
>     return NULL ;
>     }
>     }
>
>     void savePolyToFile( const Polyhedron& p )
>     {
>     std::ofstream fout( "out.off" ) ;
>     fout << p ;
>     fout.close() ;
>     }
>
>     int main()
>     {
>     Polyhedron* p1 = loadPolyFromFile( "a.off" ) ;
>     Polyhedron* p2 = loadPolyFromFile( "a2.off" ) ;
>     Polyhedron* p3 = loadPolyFromFile( "b.off" ) ;
>
>     if ( !p1 || !p2 || !p3 )
>     {
>     std::cerr << "Error loading files..." << std::endl ;
>     exit( 1 ) ;
>     }
>
>     Nef_polyhedron n1( *p1 ) ;
>     if ( !n1.is_simple() || !n1.is_valid() )
>     {
>     std::cerr << "n1 is not a 2-manifold." << std::endl ;
>     exit( 1 ) ;
>     }
>     Nef_polyhedron n2( *p2 ) ;
>     if ( !n2.is_simple() || !n2.is_valid() )
>     {
>     std::cerr << "n2 is not a 2-manifold." << std::endl ;
>     exit( 1 ) ;
>     }
>     Nef_polyhedron n3( *p3 ) ;
>     if ( !n3.is_simple() || !n3.is_valid() )
>     {
>     std::cerr << "n3 is not a 2-manifold." << std::endl ;
>     exit( 1 ) ;
>     }
>     Nef_polyhedron n = n1 - n2 - n3 ; // <-- Crashes here...
>
>     if ( n.is_simple() )
>     {
>     Polyhedron p ;
>     n.convert_to_Polyhedron( p ) ;
>     savePolyToFile( p ) ;
>     }
>     else
>     {
>     std::cerr << "N1 is not a 2-manifold." << std::endl;
>     }
>
>     // Clean up.
>     delete p1 ;
>     delete p2 ;
>     delete p3 ;
>     exit( 0 ) ;
>     }