CGAL users discussion list

[Andrew Crozier <>]

Hi Benjamin,

Thanks very much for your fast reply!

Would use of the 'Polygon soup' functions as described in the documentation (http://doc.cgal.org/latest/Polygon_mesh_processing/index.html#PolygonSoups) be a suitable preprocessing step to robustly account for this issue?

Best wishes,
Andrew

On 11/02/16 20:19, Benjamin Kehlet wrote:

Hi Andrew

The triangles in your files are not properly oriented. This leads to triangles sharing halfedges which is not allowed in a halfedge based data structure. In fact all the triangles in the plane z=2.5 should be flipped. See eg.

Line 1148: 3 745 739 251

Line 1980: 3 739 743 745

These triangles share an edge from vertex 745 to vertex 739.

Attached is a repaired version. I am able to generate a mesh from this file without problems.

Hope this helps!

Best regards

Benjamin Kehlet

On 11 February 2016 at 19:03, Andrew Crozier <> wrote:
Hi,

I am using the 3D mesh generation code as part of my workflow for building finite element models of the heart, but have run into a bit of bother with one aspect of it.

I am attempting to mesh a 3D polyhedral surface as in the example in the Mesh3 documentation:
http://doc.cgal.org/latest/Mesh_3/index.html#Mesh_33DPolyhedralDomains

When running this example, but only changing the input .off surface file to the attached 'slice.off' (and scaling the size parameters appropriately to correspond to the size of the input mesh), I get a segmentation fault in:

Program received signal SIGSEGV, Segmentation fault.
0x0000000000494a60 in CGAL::Triangle_accessor_3<CGAL::Polyhedron_3<CGAL::Epick, CGAL::Polyhedron_items_3, CGAL::HalfedgeDS_default, std::allocator<int> >, CGAL::Epick>::triangle(CGAL::internal::In_place_list_const_iterator<CGAL::HalfedgeDS_in_place_list_face<CGAL::I_Polyhedron_facet<CGAL::HalfedgeDS_face_base<CGAL::HalfedgeDS_list_types<CGAL::Epick, CGAL::I_Polyhedron_derived_items_3<CGAL::Polyhedron_items_3>, std::allocator<int> >, CGAL::Boolean_tag<true>, CGAL::Plane_3<CGAL::Epick> > > >, std::allocator<CGAL::HalfedgeDS_in_place_list_face<CGAL::I_Polyhedron_facet<CGAL::HalfedgeDS_face_base<CGAL::HalfedgeDS_list_types<CGAL::Epick, CGAL::I_Polyhedron_derived_items_3<CGAL::Polyhedron_items_3>, std::allocator<int> >, CGAL::Boolean_tag<true>, CGAL::Plane_3<CGAL::Epick> > > > > > const&) const [clone .isra.1304] ()

However, when I run with the attached 'cube.off', I get no such error, and the mesh generates successfully.

I suspect that there may be an issue with my input file, but having checked that the number of polys and points is correct, and that none of the polys contain out-of-range points, I am fairly stumped.

If anyone here is able to have a look at my input files and/or suggest further action, I would appreciate it!

Best wishes,
Andrew Crozier

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Andrew Crozier

+43 316 380 7759

Postdoctoral Researcher
Institute for Biophysics
Medical University of Graz