CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Note that depending on the CGAL version you are using, you might need
to manually call tree.accelerate_distance_queries() before doing any
distance queries (since CGAL 5.1 it should be ON by default).

If it is too slow, you will indeed need something approximating the 
inflated volume (if it makes sense you can use mesh_3 to generate it
like it is done in the demo here:
https://github.com/CGAL/cgal/blob/master/Polyhedron/demo/Polyhedron/Plugins/Surface_mesh/Offset_meshing_plugin.cpp)

Sebastien.


On 9/29/20 5:29 PM, "Grimm, Raphael (IAR)" ( via 
cgal-discuss Mailing List) wrote:
> Hi,
> Thanks for the idea, but the problem with a distance query is:
> * it is slow (since it extract more information, than the binary label I
> need for my application)
> * after the query, I do not know whether the point is inside or outside of
> the mesh (so I need to perform the inside check anyways)
>
> To check how much slower a distance query is, I wrote some test code (it is
> attached).
>
> If I run it with mesh (21965 vertices, 43926 faces, roughly a cube), then
> the tree version takes much longer (x200+ times) than the check whether the
> point is inside of the mesh.
> This test has to be very fast, since I have a lot of query points.
>
> Hence I need some way to inflate my mesh.
>
> Maybe you or someone else has another idea.
>
> Best regards,
>
> Raphael.
>
> -----Original Message-----
> From:  <> On
> Behalf Of "Sebastien Loriot (GeometryFactory)"
> Sent: Wednesday, 23 September, 2020 18:36
> To: 
> Subject: Re: [cgal-discuss] minkowski_sum_3 segfault
>
> Did you try the AABB-tree and the closest_point() method?
>
> https://doc.cgal.org/latest/AABB_tree/#title6
>
> Best regards,
>
> Sebastien.
>
> On 9/23/20 4:17 PM, "Grimm, Raphael (IAR)" ( via
> cgal-discuss Mailing List) wrote:
> > Hello,
> >
> > I have a non-convex mesh and want to check whether a point is within a
> > certain distance of it. Since distance queries are slow, I decided to
> > inflate the mesh and check whether the point is inside.
> >
> > Scaling does not work, since my mesh is concave.
> >
> > I did some looking around and came across minkowski_sum_3. I am
> > planning to use a sphere to inflate my original mesh by using
> minkowski_sum_3.
> > I wrote some simple test for minkowski_sum_3 that adds a tetrahedron
> > to a cube (code is attached).
> >
> > This test crashes with a segfault. Here is the stack trace:
> >
> > 1  CGAL::SNC_FM_decorator<CGAL::SNC_structure<CGAL::Epick,
> > CGAL::SNC_indexed_items,
> > bool>>::determine_facet
>
> > stl_vector.h                           805  0x55555559244a
> >
> > 2  CGAL::SNC_FM_decorator<CGAL::SNC_structure<CGAL::Epick,
> > CGAL::SNC_indexed_items,
> > bool>>::create_facet_objects
>
> > In_place_list.h                        84   0x5555555a0dea
> >
> > 3  CGAL::SNC_external_structure<CGAL::SNC_indexed_items,
> > CGAL::SNC_structure<CGAL::Epick, CGAL::SNC_indexed_items,
> > bool>>::categorize_facet_cycles_and_create_facets
> > stl_list.h                             953  0x5555555a16d7
> >
> > 4  CGAL::SNC_external_structure<CGAL::SNC_indexed_items,
> > CGAL::SNC_structure<CGAL::Epick, CGAL::SNC_indexed_items,
> > bool>>::build_external_structure
> > In_place_list.h                        310  0x5555555c3417
> >
> > 5  CGAL::Nef_polyhedron_3<CGAL::Epick, CGAL::SNC_indexed_items,
> > bool>::build_external_structure
>
> > SNC_const_decorator.h                  125  0x5555555f6188
> >
> > 6  CGAL::Nef_polyhedron_3<CGAL::Epick, CGAL::SNC_indexed_items,
> > bool>::delegate
>
> > Nef_polyhedron_3.h                     1071 0x5555555f6188
> >
> > 7
> > CGAL::bipartite_nary_union_sorted_combined<CGAL::Nef_polyhedron_3<CGAL
> > ::Epick,
> > CGAL::SNC_indexed_items,
> > bool>>
> > bipartite_nary_union_sorted_combined.h 214  0x5555555f6188
> >
> > 8  CGAL::minkowski_sum_3<CGAL::Nef_polyhedron_3<CGAL::Epick,
> > CGAL::SNC_indexed_items, bool>>
>                                           In_place_list.h
>      
> > 309  0x5555555f7384
> >
> > 9
> > main
>
> >             minkowski_sum_3.cpp                    81   0x55555555d8df
> >
> > 10
> > __libc_start_main
>
> > libc-start.c                           310  0x7ffff69ccb97
> >
> > 11 _start
> >
> > I have two questions:
> >
> > 1.Is there a better (more efficient) way to do this?
> >
> > 2.If not, how can I fix the segfault / what am I doing wrong?
> >
> > I appreciate any hints.
> >
> > Best
> >
> > Raphael
> >
> > ----
> >
> > Karlsruhe Institute of Technology (KIT)
> >
> > Institute for Anthropomatics and Robotics (IAR)
> >
> > High Performance Humanoid Technologies (H2T)
> >
> > Raphael Grimm (M.Sc.)
> >
> > Research Scientist
> >
> > Adenauerring 2
> >
> > Building 50.20, Room 334
> >
> > 76131 Karlsruhe, Germany
> >
> > Phone: +49 721 608-47133
> >
> > Fax: +49 721 608-48270
> >
> > Email: 
> >
> > Web: https://www.humanoids.kit.edu
> >
> > KIT - The Research University in the Helmholtz Association
>
> --
> You are currently subscribed to cgal-discuss.
> To unsubscribe or access the archives, go to
> https://sympa.inria.fr/sympa/info/cgal-discuss