CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Hello,

As documented here:
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Nef_3/Chapter_main.html#Subsection_27.5.4
If you use the constructor of nef from a polyhedron, then the polyhedron
must be a 2-manifold. sphere0.off is definitely not (you have duplicated 
vertices and probably autointersection).

You can use the function OFF_to_nef_3
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Nef_3_ref/Function_OFF_to_nef_3.html
to convert sphere0.off to a valid nef. However, the resulting nef is not
simple. The union operation can be computed but as the result is also
not simple you cannot export it as a polyhedron.

I simplified sphere0.off and your original code was working out of the
box.


Sebastien.

Jayesh Salvi wrote:
> Ok, I have managed to put together a simple example that reproduces
> the crash I reported earlier.
>
> Attached is a simple .cpp program which reads two polyhedra from off
> files and performs union operation on them. Also attached are the two
> off files that you have to pass as argument to the program, in order
> to make it crash.
>
> I tested against CGAL 3.8.
> --
> Jayesh
>
>
>
> On Wed, Jun 1, 2011 at 5:16 PM, Sebastien Loriot (GeometryFactory)
> <>
>  wrote:
> > Sorry cannot debug with just this.
> >
> >
> > S.
> >
> > Jayesh Salvi wrote:
> > > Ok,
> > >
> > > I've made some progress on this.
> > >
> > > The wild behavior was probably due to our memory allocation bugs.
> > > After replacing malloc, by calloc the erratic behavior went away and I
> > > got a nice segmentation fault. Here is the stack trace:
> > >
> > > (gdb) bt
> > > #0  0xb7796cf5 in
> > > CGAL::SNC_FM_decorator<CGAL::SNC_structure<CGAL::Epeck,
> > > CGAL::SNC_indexed_items, bool>
> > > > ::create_facet_objects(CGAL::Plane_3<CGAL::Epeck> const&,
> > > std::_List_iterator<CGAL::Object>, std::_List_iterator<CGAL::Object>)
> > > const
> > >    () from build/libcsgop.so
> > >    #1  0xb7783dc7 in
> > > CGAL::SNC_external_structure<CGAL::SNC_indexed_items,
> > > CGAL::SNC_structure<CGAL::Epeck, CGAL::SNC_indexed_items, bool>
> > > > ::categorize_facet_cycles_and_create_facets() const () from
> > > build/libcsgop.so
> > >    #2  0xb7789fcb in void
> > > CGAL::SNC_external_structure<CGAL::SNC_indexed_items,
> > > CGAL::SNC_structure<CGAL::Epeck, CGAL::SNC_indexed_items, bool>
> > > > ::build_after_binary_operation<CGAL::ID_support_handler<CGAL::SNC_indexed_items,
> > > CGAL::SNC_decorator<CGAL::SNC_structure<CGAL::Epeck,
> > > CGAL::SNC_indexed_items, bool> > >
> > > > (CGAL::ID_support_handler<CGAL::SNC_indexed_items,
> > > CGAL::SNC_decorator<CGAL::SNC_structure<CGAL::Epeck,
> > > CGAL::SNC_indexed_items, bool> > >&) () from build/libcsgop.so
> > >    #3  0xb7775484 in void
> > > CGAL::Binary_operation<CGAL::SNC_structure<CGAL::Epeck,
> > > CGAL::SNC_indexed_items, bool>
> > > > ::operator()<CGAL::Nef_polyhedron_3<CGAL::Epeck,
> > > CGAL::SNC_indexed_items,
> > >
> > > bool>::OR>(CGAL::SNC_point_locator<CGAL::SNC_decorator<CGAL::SNC_structure<CGAL::Epeck,
> > > CGAL::SNC_indexed_items, bool> > >*, CGAL::SNC_structure<CGAL::Epeck,
> > > CGAL::SNC_indexed_items, bool> const&,
> > >
> > > CGAL::SNC_point_locator<CGAL::SNC_decorator<CGAL::SNC_structure<CGAL::Epeck,
> > > CGAL::SNC_indexed_items, bool> > > const*,
> > > CGAL::SNC_structure<CGAL::Epeck, CGAL::SNC_indexed_items, ---Type
> > > <return> to continue, or q <return> to quit---
> > >    bool> const&,
> > >
> > > CGAL::SNC_point_locator<CGAL::SNC_decorator<CGAL::SNC_structure<CGAL::Epeck,
> > > CGAL::SNC_indexed_items, bool> > > const*,
> > > CGAL::Nef_polyhedron_3<CGAL::Epeck, CGAL::SNC_indexed_items, bool>::OR
> > > const&) () from build/libcsgop.so
> > >    #4  0xb776e6a6 in CGAL::Nef_polyhedron_3<CGAL::Epeck,
> > > CGAL::SNC_indexed_items,
> > > bool>::join(CGAL::Nef_polyhedron_3<CGAL::Epeck,
> > > CGAL::SNC_indexed_items, bool> const&) const () from build/libcsgop.so
> > >    #5  0xb7769efc in CGAL::Nef_polyhedron_3<CGAL::Epeck,
> > > CGAL::SNC_indexed_items,
> > > bool>::operator+=(CGAL::Nef_polyhedron_3<CGAL::Epeck,
> > > CGAL::SNC_indexed_items, bool> const&) () from build/libcsgop.so
> > >    #6  0xb7764308 in csgop () from build/libcsgop.so
> > > ... application specific frames ...
> > >
> > > Does that give any clue?
> > > --
> > > Jayesh
> > >
> > >
> > >
> > > On Tue, May 31, 2011 at 7:15 PM, Jayesh Salvi 
> > > <>
> > > wrote:
> > > > Let me see if I can put together some minimal c++ code to demo this.
> > > > --
> > > > Jayesh
> > > >
> > > >
> > > >
> > > > On Tue, May 31, 2011 at 11:31 AM, Sebastien Loriot (GeometryFactory)
> > > > <>
> > > >  wrote:
> > > > > Any complete minimal example showing the problem?
> > > > >
> > > > > S.
> > > > >
> > > > > Jayesh Salvi wrote:
> > > > > > ^ Bump ^
> > > > > >
> > > > > > Any thoughts?
> > > > > > --
> > > > > > Jayesh
> > > > > >
> > > > > >
> > > > > >
> > > > > > On Sun, May 29, 2011 at 4:43 PM, Jayesh Salvi 
> > > > > > <>
> > > > > > wrote:
> > > > > > > Hello,
> > > > > > >
> > > > > > > In my program I am creating two polyhedrons from two meshes (In this
> > > > > > > case a cube and a sphere). Then I convert them to Nef Polyhedra and
> > > > > > > apply union (+) operation on them. I then convert the returned Nef
> > > > > > > Polyhedron into a Polyhedron_3, but before doing that I run
> > > > > > > is_simple() check (just so that if it is not simple, I can generate an
> > > > > > > error message, instead of assertion failure crash during the
> > > > > > > conversion process).
> > > > > > >
> > > > > > > In this particular case - with a cube and sphere of specific
> > > > > > > geometries - I observed that after some time the program starts
> > > > > > > occupying a lot of memory and consumes most of the CPU. From the top
> > > > > > > utility, I can see that the process is taking >90% memory and >90%
> > > > > > > CPU. To see what's going on, I put cout statements at various places
> > > > > > > to see during which part of the program does this start to happen. I
> > > > > > > was surprised to find out that this happens when I call is_simple()
> > > > > > > check on the nef polyhedron. At this point either I have to kill the
> > > > > > > process or the system terminates it.
> > > > > > >
> > > > > > > I tried to run the program through valgrind, but as I read elsewhere
> > > > > > > valgrind can't be used with CGAL programs because of floating point
> > > > > > > issues.
> > > > > > >
> > > > > > > Do you have any suggestions how can I proceed to debug this?
> > > > > > >
> > > > > > > Thanks in advance.
> > > > > > >
> > > > > > > (My project is available at http://jayesh3.github.com/cadmium/ I can
> > > > > > > provide instructions on how to reproduce the issue, if you need)
> > > > > > > --
> > > > > > > Jayesh
> > > > > --
> > > > > You are currently subscribed to cgal-discuss.
> > > > > To unsubscribe or access the archives, go to
> > > > > https://lists-sop.inria.fr/wws/info/cgal-discuss
> >
> > --
> > You are currently subscribed to cgal-discuss.
> > To unsubscribe or access the archives, go to
> > https://lists-sop.inria.fr/wws/info/cgal-discuss

OFF
6 8 0
 0 0  2
 2 0  0
 0 0 -2
-2 0  0
0 2 0
0 -2 0
 
 3 1 4 0
 3 2 4 1
 3 0 4 3
 3 2 3 4

 3 1 0 5
 3 2 1 5
 3 0 3 5
 3 2 5 3