CGAL users discussion list

[Peter Hachenberger <>]

If they are small. I personally would prefer off files. 

On Wed, 2006-12-13 at 13:14 +0100, FEYEL Frederic. wrote:
> Humm, under which form could I send this datas to the list. Two vrml files ?
> 
> 
> Peter Hachenberger a écrit :
> > Can you also sent the input data for which the program crashed.
> >
> > Peter
> >
> > On Wed, 2006-12-13 at 10:23 +0100, FEYEL Frederic. wrote:
> >   
> >> First of all, thank you very much for your help. It is a real pleasure
> >> to see this reactivity !
> >>
> >> My program is really simple:
> >>
> >>   to_cgal(mesh1,P1); to_cgal(mesh2,P2);
> >>
> >>   if (!P1.is_closed() || !P2.is_closed() ) ERROR("Supplied meshes are
> >> not closed");
> >>
> >>   Nef_polyhedron N1(P1);
> >>   Nef_polyhedron N2(P2);
> >>
> >>   Nef_polyhedron N3;
> >>
> >>   N3=N1-N2;
> >>   if (!N3.is_simple()) ERROR("Resulting shape is not a 2-manifold");
> >>   N3.convert_to_Polyhedron(P3);
> >>
> >>  
> >>
> >> The to to_cgal(...) methods allows the conversion from  my own data
> >> structure: it constructs the Polyhedron, knowing the surface mesh,
> >> using the following piece of code:
> >>
> >>   Build_poly_from_utility_mesh<HalfedgeDS> builder(mesh);
> >>   P.delegate(builder);
> >>
> >>
> >> where the Build_poly_from_utility_mesh contains (all UTILITY_xxxxx
> >> classes are my datastructures, containing nodes, elements, etc...
> >> In the test, all those UTILITY_ELEMENT are made of 3-nodes shell 
> >> elements) :
> >>
> >>    void operator()( HDS& hds) {
> >>       CGAL::Polyhedron_incremental_builder_3<HDS> B(hds);
> >>
> >>       B.begin_surface(mesh->nodes.size(),mesh->elements.size());
> >>
> >>       for (int inode=0;inode<mesh->nodes.size();inode++) {
> >>         VECTOR &pos=mesh->nodes[inode]->position;
> >>         Point p(pos[0],pos[1],pos[2]);
> >>         B.add_vertex(p);
> >>       }
> >>
> >>       for (int ielem=0;ielem<mesh->elements.size();ielem++) {
> >>         UTILITY_ELEMENT &an_elem=*mesh->elements[ielem];
> >>
> >>         B.begin_facet();
> >>         for (int inode=0;inode<an_elem.nodes.size();inode++)
> >>           B.add_vertex_to_facet(an_elem.nodes[inode]->give_rank());
> >>         B.end_facet();
> >>       }
> >>
> >>       B.end_surface();
> >>     }
> >>
> >>
> >> I think that the creation of the Polyhedron works well, because the VRML
> >> exported file looks ok in an
> >> independent VRML viewer.
> >>
> >> Once again, thank you very much for your help.
> >>
> >> Frédéric.
> >>
> >>
> >>
> >> Andreas Fabri a écrit :
> >>     
> >>> Please post your test program if it is short.
> >>>
> >>> andreas
> >>>
> >>> Frédéric FEYEL wrote:
> >>>       
> >>>> Thank you for your advice.
> >>>>
> >>>> I changed my closed surface so that it contains only 3-nodes
> >>>> facets, so that all facets are obviously planar.
> >>>>
> >>>> However, the same problem is still there:
> >>>>
> >>>> CGAL error: assertion violation!
> >>>> Expr: pe_prev->facet()->plane().
> >>>> has_on(pe_prev->opposite()->vertex()->point())
> >>>> File: 
> >>>> ./cgal_build/CGAL-3.2.1/include/CGAL/Nef_3/polyhedron_3_to_nef_3.h
> >>>>
> >>>> Does anyone has some extra clues ?
> >>>>
> >>>> Thank you very much for your help,
> >>>>
> >>>> Best Regards,
> >>>>
> >>>> Frederic.
> >>>>
> >>>> Andreas Fabri a écrit :
> >>>>         
> >>>>> Hello,
> >>>>>
> >>>>> When you have facets with more than three vertices they must be
> >>>>> coplanar, which might not be given if their coordinates are doubles.
> >>>>> The solution is to either make them coplanar, or to triangulate
> >>>>> the faces.
> >>>>>
> >>>>> best regards,
> >>>>>
> >>>>> andreas
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> 
> >>>>>  wrote:
> >>>>>           
> >>>>>> Hello,
> >>>>>>
> >>>>>> I am very new to CGAL, and I am wondering if it is possible to do
> >>>>>> solid/solid intersections.
> >>>>>>
> >>>>>> It is funny to see that infact, I have the same question as Cedric
> >>>>>> Le Maitre (he sent a mail today)...
> >>>>>>
> >>>>>> More precisely, I have two solids described by two closed Polyhedra
> >>>>>> (using 3 and 4 nodes faces).
> >>>>>>
> >>>>>> I would like to get the Polyhedra that represents the difference
> >>>>>> between
> >>>>>> the two solids.
> >>>>>>
> >>>>>> I tried using the Nef_polyhedron_3 classes :
> >>>>>>
> >>>>>> 1- construct two Polyhedron
> >>>>>> 2- construct the Nef_polyhedron from the 2 polyhedron
> >>>>>> 3- intersect the 2 Nef_polyhedron
> >>>>>> 4- convert the result back to a Polyhedron
> >>>>>>
> >>>>>> When I construct the nef associated with one of the Polyhedrons, I
> >>>>>> get the following error :
> >>>>>>
> >>>>>> CGAL error: assertion violation!
> >>>>>> Expr: pe_prev->facet()->plane().
> >>>>>> has_on(pe_prev->opposite()->vertex()->point())
> >>>>>> File:
> >>>>>> ./cgal_build/CGAL-3.2.1/include/CGAL/Nef_3/polyhedron_3_to_nef_3.h
> >>>>>> Line: 151
> >>>>>>
> >>>>>> I had a look in this file, but the error is not so obvious, at
> >>>>>> least for
> >>>>>> a 'CGAL-beginner' like me.
> >>>>>>
> >>>>>>
> >>>>>> Could anyone guide me, and tell me if such operation is available in
> >>>>>> CGAL, and if yes, how to achieve it ? Any help would be greatly
> >>>>>> appreciated.
> >>>>>>
> >>>>>>
> >>>>>> Best Regards,
> >>>>>>
> >>>>>> Frederic.
> >>>>>>
> >>>>>>
> >>>>>>             
> >>>>
> >>>>
> >>>>         
> >
> >
> >   
>