CGAL users discussion list

[Peter Hachenberger <>]

Hi Max,

the problems have nothing to do with the new functionality but with
the kernel. If you modify for off-file with floating-point coordinates
as input, you must use the Exact_predicates_exact_constructions_kernel.

About your other question. To find out how to get all the shells, you
should study the incidence structure. Look at:

http://www.cgal.org/Manual/3.3/doc_html/cgal_manual/Nef_3/Chapter_main.html#Subsection_18.7.2
http://www.cgal.org/Manual/3.3/doc_html/cgal_manual/Nef_3_ref/Class_Nef_polyhedron_3-Traits---Volume.html

Peter


On Fri, 2008-01-18 at 10:44 +0800, Max wrote:
> Hello Peter,
> 
> I've tested with three OFF models as attached.
> The output are as follows:
> 
> 1. robocat_deci.off
> I got only a bunch of "Error !!!!!!!!!!!!!!!!!!!!!!!" then 
> the program terminated abnormally.
> 
> 2. torus_tri.off 
> The program terminated abnormally without saying anything.
> 
> 3. Simple.off
> The program said:
> old impl 0.07
> new impl 0.06
> and then ends normally.
> 
> My platform:
> CGAL 3.3.1
> Windows XP/SP2
> VS2005 without SP1
> 
> Build under release mode.
> 
> One more question: If the code runs correctly, how can I get
> the group of single closed polyhedrona I needed?
> 
> p.s., I've slightly modified the program to get a model in OFF format.
> it's also attached. perhaps some problem comes from the conversion 
> from a polyhedron to a nef_3.
> 
> B/Rgds
> Max
> 
> >Hello Peter,
> >
> >Thank you very much for you prompt and detailed reply!
> >I'll test your code addition and post the result asap.
> >
> >B/Rgds
> >Max
> >
> >>Hi Max,
> >>
> >>I got this question frequently off late. For this reason I implemented a
> >>new function. Add the attached file shell_to_nef_3.h to your
> >>include/CGAL/Nef_3 directory and add the following code to
> >>Nef_polyhedron_3.h:
> >>
> >>Nef_polyhedron_3(const Nef_polyhedron& N,
> >>                 SFace_const_iterator sf)
> >>{
> >>  SNC_structure rsnc;
> >>  *this = Nef_polyhedron_3(rsnc, new SNC_point_locator_default, false);
> >>  initialize_infibox_vertices(EMPTY);
> >>  shell_to_nef_3(N, sf, snc());
> >>  build_external_structure();
> >>  simplify();
> >>  CGAL::Mark_bounded_volumes<Nef_polyhedron_3> mbv(true);
> >>  delegate(mbv);
> >>  set_snc(snc());
> >>}
> >>
> >>There is another file attached, which demonstrates the usage. This
> >>program compares two methods of conversion, an old and simple one with
> >>the new one. If you don't use CGAL 3.3.1, you won't have the code for
> >>the old implementation and need to comment/ignore the first part of the
> >>program. I originally wrote the code to work for closed inner shells,
> >>but maybe it also works non-closed shells and outer shells. Please tell
> >>me how it works.
> >>
> >>Peter
> >>
> >>
> >>On Thu, 2008-01-17 at 19:18 +0800, Max wrote:
> >>> Hi all,
> >>> 
> >>> I know if a Nef_polyhedron is simple (or, in other words,
> >>> a manifold), it could be converted to a single polyhedron 
> >>> with the method: 
> >>> 
> >>> Nef_polyhedron::convert_to_Polyhedron ( Polyhedron& P) 
> >>> 
> >>> My question is, if N is not a single manifold, but still finite, 
> >>> is there a way in CGAL to convert it into a group of polyhedra?
> >>> 
> >>> Thanks for any help.
> >>> 
> >>> B/Rgds
> >>> Max
> >>> 
> >>-- 
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