CGAL users discussion list

[Zhanghong Tang <>]

Hi Dr. Lu,

Thank you very much for your kindly reply. The OFF files are generated by CGAL code after some bool operations. Is there any funciton in CGAL package to output polyhedron/OFF file to let it can be used by mesher? Do you have any suggestion to simplify (for example, remove very closed nodes) the output polyhedron?

Thanks,
Zhanghong Tang

> Date: Sat, 15 Sep 2012 08:38:27 -0700
> From:
> To:
> Subject: [cgal-discuss] RE: Error in CGAL bool operation to the OFF files
>
> Hi Tang,
>
> I could see the source of the problem. You have at least two faces
> (triangles) in a1.off with vertices they are linear combination.
>
> (a1.off)
> Line 356 defines wrong face --> 3 133 65 106
> Line 448 defines wrong face --> 3 123 133 106
>
> Vertices 106 and 133 has the same value.
>
> Line 109 defines vertex 106: -0.045 5.51091e-018 -0.45
> Line 136 defines vertex 133: -0.045 5.51091e-018 -0.45
>
> The conversion from Polyhedron_3 to Nef_polyhedron (line 53 of your main.cpp
> source code) requires to calculate the normals for each of faces in your
> polyhedron. It's not possible to calculate the normal for the above faces.
>
> Your program should throw an error message "Error !!!!!" in line 106 of
> polyhedron_3_to_nef_3.h
>
> Later, the program crash in following assert:
>
> terminate called after throwing an instance of 'CGAL::Assertion_exception'
> what(): CGAL ERROR: assertion violation!
> Expr: pe_prev->is_border() ||
> !internal::Plane_constructor<Plane>::get_plane(pe_prev->facet(),pe_prev->facet()->plane()).is_degenerate()
> File: ../../dev/CGAL-4.1-beta1/include/CGAL/Nef_3/polyhedron_3_to_nef_3.h
> Line: 252
>
> These faces in your file define a segment instead of a triangle due to the
> linear combination.
>
> Regards,
> Juan Luis.
>
>
>
> --
> View this message in context: http://cgal-discuss.949826.n4.nabble.com/Error-in-CGAL-bool-operation-to-the-OFF-files-tp4655853p4655861.html
> Sent from the cgal-discuss mailing list archive at Nabble.com.
>
> --
> You are currently subscribed to cgal-discuss.
> To unsubscribe or access the archives, go to
> https://sympa.inria.fr/sympa/info/cgal-discuss
>
>