CGAL users discussion list

[Phil Weir <>]

On 10/17/2013 05:57 PM, Garth N. Wells wrote:
> I'm trying to create a volume mesh of a polyhedron with many faces, 
> but I keep getting the error:
>
> construct initial points:
> 8/8 initial point(s) found...
> Start surface scan...end scan. [Bad facets:12]
>
> Refining Surface...
> Legende of the following line: (#vertices,#steps,#facets to 
> refine,#tets to refine)
> (3286,3277,0,0) (2847.9 vertices/s))))
> Total refining surface time: 1.15069s
>
> Start volume scan...end scan. [Bad tets:9713]
>
> Refining...
> Legende of the following line: (#vertices,#steps,#facets to 
> refine,#tets to refine)
> (7617,4330,0,37339) (11173.1 vertices/s)terminate called after 
> throwing an instance of 'CGAL::Assertion_exception'
>   what():  CGAL ERROR: assertion violation!
> Expr: !r_tr_.is_infinite(*cell_it)
> File: /usr/include/CGAL/Mesh_3/Refine_cells_3.h
> Line: 385
>
>
> What I'm doing is surface meshing a sphere, converting the surface 
> mesh to a polyhedron, and trying to generate a volume mesh of the 
> polyhedron (the motivation is to add/subtract polyhedra to create more 
> complicated domains). The code that reproduces the error (using CGAL 
> 4.2 and GCC 4.8) is attached. The code is basically a concatenation of 
> the demos in sections 48.3.1 and 51.3.2. Any suggestions to get this 
> working?
>
> Garth

Actually, I have just had a very similar problem the last couple of 
days, same abort message - I rebuilt CGAL 4.2, with identical source to 
the working version, and it appeared. The old binary still runs fine. 
CGAL 4.2 and 4.3 show the same thing with the mesh_polyhedral_domain 
demo. A fresh compile of CGAL 4.3 on an Ubuntu 12.04 virtual box has no 
problems. As such, I suspect there may be something with library versions.

Looking through the code and running tests, it seems that this is caused 
by infinite cells, ones defining external facets, being included in the 
incident_cells in update_star_self (Refine_cells_3.h:371 in 4.3) This 
has a CGAL_assertion that triggers the abort.

update_star does not have an abort, just an if statement. As a 
workaround, I have defined 
CGAL_MESH_3_USE_OLD_SURFACE_RESTRICTED_DELAUNAY_UPDATE and that seems to 
avoid it (so far).

This could be completely up the wrong street, but it may help you.

Best wishes,
Phil

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