CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 12/03/2014 02:23 PM, Per Zetterlund wrote:
> As far as I understand, it can extract
> a manifold Polyhedron as long as the the
> surface embedded in the triangulation
> actually is manifold. It does not in any
> way enforce or aid in the process of making
> the surface manifold, right?
Right.

> When I try it I get lots of errors such as
>
> CGAL::Polyhedron_incremental_builder_3<HDS>::
> add_vertex_to_facet(): input error: disconnected facet complexes at vertex 
> 352:
>             involved facets are: 1815 1814 1813 (closed cycle) and.
> terminate called after throwing an instance of 'CGAL::Assertion_exception'
>    what():  CGAL ERROR: assertion violation!
> Expr: check_protocoll == 1
> File: /usr/local/include/CGAL/Polyhedron_incremental_builder_3.h
> Line: 225
> Aborted (core dumped)
>
> I guess that is because the embedded surface
> was not manifold.

Most probably.
A simple hack is to duplicate the non-manifold vertices.

Sebastien.

>   /Per
>
>
>
>
> On Tue, Dec 2, 2014 at 1:32 PM, Sebastien Loriot (GeometryFactory)
> <>
>  wrote:
> > On 11/24/2014 09:10 AM, Per Zetterlund wrote:
> > > Hi all,
> > >
> > > This is an issue I've run into several times
> > > in different applications. Say that I have a
> > > Triangulation_3 and I do a binary labelling of
> > > the cells. Then I want to extract the interface
> > > surface between the labels as a manifold
> > > Polyhedron_3. Often it happens that that the
> > > topology of the actual triangle faces in the
> > > triangulation is not manifold. Are there any
> > > routines in CGAL to extract a manifold surface
> > > from a triangulation that (in some sense) is
> > > close to the true interface surface?
> >
> >
> > There is nothing working out-of-the-box but looking
> > at the file CGAL/IO/Complex_2_in_triangulation_3_polyhedron_builder.h
> > should give you ideas of how a manifold surface mesh is extracted
> > from a 3D triangulation.
> >
> > Sebastien.
> >
> > > Any ideas?
> > >
> > >    /Per
> >
> >
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