CGAL users discussion list

[Frédéric FEYEL <>]

Humm I dont know what you mean by small.

I attached my two off files, comrpessed using gzip. The biggest
of the 2 file weights 11 Kb.

If you consider them as too big, I am of course ready to lower
the surface discretization.

The two off files are generated by CGAL, and look good in geomview.

Thank you very much for your help and support.

Frédéric.

Peter Hachenberger a écrit :
> 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.
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>
>> >>>>
>> >>>>
>> >
>> >
>> >
>>
>
>
>

Attachment: P1.off.gz
Description: GNU Zip compressed data

Attachment: P2.off.gz
Description: GNU Zip compressed data