CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Here is an example of usage of copy_tds():

https://gist.github.com/sloriot/f9f929ce2e30b59f1b63a3cf3780159e

Are talking of filtering infinite cells?

Sebastien.


On 01/09/2019 10:25 PM, Marc Alexa wrote:
> Hi Sebastian,
>
> Thanks for your answer. I use the stream operator on both, c3t3 and 
> c3t3.triangulation and the result is identical.
>
> I was never able to downcast. I somehow don’t manage to use types that CGAL 
> understand to cast. The copy_tds function looks interesting. For now I solved 
> my problem in a more ugly way by directly filtering the stream generated by 
> c3t3.
>
> My other problem remains. c3t3 uses some peeling, but the peeled tets are 
> part of the triangulation so they still get exported.
>
> I guess, fundamentally I need to solve the following problem: given a 
> collection of tets that form a valid tet mesh with boundary. How can I 
> generate the ‘outside’ tets that CGAL expects for Triangulation 3, i.e. the 
> tets connected to the infinite vertex. Is there a simple way in CGAL to do 
> this?
>
> Thanks!
> -Marc
>
>
>
> > On 7. Jan 2019, at 08:47, Sebastien Loriot (GeometryFactory) 
> > <>
> >  wrote:
> >
> > Hi Marc,
> >
> > Did you try to dump c3t3.triangulation()? AFAIK, this should directly
> > call the operator<<() from Regular_triangulation_3 and gives you what
> > you need. I guess you could even down cast it to a given Triangulation_3
> > class.
> >
> > If you need to import it into a different triangulation type, you have
> > to do it at the TDS level by using the function copy_tds() for example.
> >
> > See here:
> > https://doc.cgal.org/latest/TDS_3/classTriangulationDataStructure__3.html#aac784b676421bd590612bb08c0a84f89
> >
> > HTH,
> >
> > Sebastien.
> >
> > On 01/05/2019 01:53 PM, Marc Alexa wrote:
> > > Dear all,
> > > I am generating a tetrahedral mesh using the suite of algorithms in Mesh_3. I 
> > > want to use the resulting mesh in my code, which is based on Triangulation_3. 
> > > The vertex and cell base classes are incompatible. My preferred way for doing 
> > > this would be writing the mesh to a file. Unfortunately, the formats of the 
> > > stream operators are different. Is there an easy way to “reduce” what is 
> > > being written by Mesh_3 to what is being expected by Triangulation_3?
> > > On a side note: I understand that if I am not using sliver exudation, the 
> > > triangulation generated by Mesh_3 will be Delaunay. This means I could export 
> > > the points only (and then reconstruct the tetrahedra). Then I only need 
> > > information on which tetrahedra are in the interior of the meshed surface. I 
> > > tried to circumvent this by using a simple convex surface, namely a sphere. 
> > > Yet even for the sphere some tetrahedra are excluded, despite clearly lying 
> > > in the interior. I do understand that the excluded tetrahedra are slivers, 
> > > but wouldn’t it make sense that a tetrahedral mesh with the boundary vertices 
> > > on the sphere contained everything inside the sphere?
> > > Best,
> > > Marc
> >
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