CGAL users discussion list

[Monique Teillaud <>]

On 07 Apr 2016, at 16:06, Pratyush Pranav <> wrote:

Hi Monique,

thanks for the mail. What you suggest sounds good below. Actually, outputting the convex hull as a polyhedron_3 would have made my life much simple. But i think there is a problem. I have additional information stored on the vertices of the triangulation. I guess when I output the convex hull as a polyhedron, i lose this additional information on the vertices?

I would “guess” the opposite, but in general I don’t trust guesses… I trust the manual better, and/or results of experiments. 

While going through the manual, I ahvent encountered the possibility of deriving polyhedron_3 from vertex_with_info_3. As far as I understand, it is only possible to derive the triangulation class from the base class of vertex with info. Any additional cues would be helpful.

I guess i could circumvent this problem if I can also inherit the polyhedron from the vertex_base_with_if_3 class ( the name of the class is not accurate probably, i am spewing it out of my mind). Do you think it is possible to inherit poly from vertex with info? I am sorry, it has been many years since i touched CGAL, and i am on a bit of shaky ground here.

Alternatively, if this is not possible,

to be checked

I guess I can work with the original triangulation by restricting myself to the simplifies on the convex hull only. I think, for this i need to devise a function that checks if a particular simplex is on the convex hull or not. I write below my idea of how to check if a particular simplex is on the hull.

— for a vertex it is trivial, because by design they are al on the surface of the sphere (or do i need additional checks?)

you can check if it is incident to the infinite vertex

can a vertex itself be incident to the infinite vertex? i "guess" again it has to be through a cell or a facet or an edge, isnt it? i wonder what i am missing here. 

I should have written adjacent, instead of incident. 

I maybe wrong, but i was not able to find if it is possible to directly access the incident cells to a facet. hence i was going through the route of the "checking the edges of the facets". could you please confirm if it is indeed a possiblitiy to access the cells incident to a facet directly?

How can you manage to access a facet without knowing at least one of its incident cells?

http://doc.cgal.org/latest/TDS_3/classTriangulationDataStructure__3.html#ad6a20b45e66dfb690bfcdb8438e9fcae

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Monique Teillaud 
http://www.loria.fr/~teillaud/ 
INRIA Nancy - Grand Est, LORIA 
Institut National de Recherche en Informatique et Automatique