CGAL users discussion list

[Sebastien Loriot <>]

The CGAL-BGL reading function returns false, so it means that the input 
is not a valid manifold surface.

If you using the PMP function:

#include <CGAL/Polygon_mesh_processing/IO/polygon_mesh_io.h>
if (!CGAL::Polygon_mesh_processing::IO::read_polygon_mesh(filename, 
polygon_mesh)) {
...
}

some repair operations will be done to solve non-manifoldness (to the
price of adding duplicated simplices and thus self-intersections).

More details here:
https://doc.cgal.org/latest/Polygon_mesh_processing/group__PMP__IO__grp.html#gac5b3295bd1b6375628a46d1fbaf7e881

Sebastien.

On 8/28/23 08:54, Claus Volko ( via cgal-discuss 
Mailing List) wrote:
> I used the attached program and got an error message.
>
> Am Mo., 28. Aug. 2023 um 08:48 Uhr schrieb Sebastien Loriot 
> < <>>:
>
>     I did not have any issue opening the shared file.
>     Could you please share a minimal example I can compile and that shows
>     the error so that I can run on my side?
>
>     Best,
>
>     Sebastien.
>
>     On 8/28/23 08:28, Claus Volko (
>     <> via cgal-discuss
>     Mailing List) wrote:
>      > Yes, I uploaded it to:
>      > http://www.21stcenturyheadlines.com/temp/Scene_obj.zip
>     <http://www.21stcenturyheadlines.com/temp/Scene_obj.zip>
>      > <http://www.21stcenturyheadlines.com/temp/Scene_obj.zip
>     <http://www.21stcenturyheadlines.com/temp/Scene_obj.zip>>
>      >
>      > Am Mo., 28. Aug. 2023 um 08:06 Uhr schrieb Sebastien Loriot
>      > < <>
>     < <>>>:
>      >
>      >     Could you share such an obj file that CGAL cannot open?
>      >
>      >     Thanks,
>      >
>      >     Sebastien.
>      >
>      >     On 8/27/23 17:03, Claus Volko (
>     <>
>      >     < <>> via
>     cgal-discuss
>      >     Mailing List) wrote:
>      >      > We are trying to make OBJ files saved from Google Maps HD
>     compatible
>      >      > with CGAL 5.6 for Shape Detection (Region Growing). On opening
>      >     the OBJ
>      >      > file I get an error message that does not explain what is
>     wrong, but
>      >      > after converting to OFF it is more verbose:
>      >      >
>      >      > CGAL::Polyhedron_incremental_builder_3<HDS>::
>      >      > lookup_halfedge(): input error: facet 49 shares a halfedge
>     from
>      >     vertex
>      >      > 145 to vertex 146 with facet 48.
>      >      >
>      >      > Polyhedron_scan_OFF<Traits>::
>      >      > operator()(): input error: facet 50 has fewer than 3 vertices.
>      >      > ERROR: cannot read the input file!
>      >      >
>      >      > I wrote a short program in C# that should fix the problem
>      >     (attached).
>      >      > However, the result is a file that is somewhat
>     degenerated: the
>      >     number
>      >      > of planes is equal to the number of faces. This cannot be
>     used.
>      >      >
>      >      > Does anybody have an idea how else this could be fixed?
>      >      >
>      >      > --
>      >      > Dipl.-Ing. Dr. Claus D. Volko, BSc
>      >      > http://www.cdvolko.net/ <http://www.cdvolko.net/>
>     <http://www.cdvolko.net/ <http://www.cdvolko.net/>>
>      >     <http://www.cdvolko.net/ <http://www.cdvolko.net/>
>     <http://www.cdvolko.net/ <http://www.cdvolko.net/>>>
>      >      >
>      >      >
>      >      >
>      >      >
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>      > --
>      > Dipl.-Ing. Dr. Claus D. Volko, BSc
>      > http://www.cdvolko.net/ <http://www.cdvolko.net/>
>     <http://www.cdvolko.net/ <http://www.cdvolko.net/>>
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> Dipl.-Ing. Dr. Claus D. Volko, BSc
> http://www.cdvolko.net/ <http://www.cdvolko.net/>
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