CGAL users discussion list

[Monique Teillaud <>]

Le 06/05/15 03:06, Adam Getchell a écrit :
> Hello all,
>
> I’m attempting to implement the (2,6) move which may be described
> pictorially as:

Hi Adam,

> My questions:
>
> 1. Is it correct to delete the two old cells before creating the new ones?

It is correct, as long as you don't lose their neighbors, which will be 
neighbors of the new cells.
However it might be more efficient not to delete them, but just modify 
them, and create only the 4 additional cells needed.
You may want to have a look at how flips are implemented in 
Triangulation_data_structure_3.h

> 2. Is there a way to create a vertex without inserting it into the
> Delaunay triangulation?

You must certainly not insert a point in the Delaunay triangulation, in 
general it cannot give you what you want. You should only use and patch TDS.

look for create_vertex in
http://doc.cgal.org/latest/TDS_3/classTriangulationDataStructure__3.html
Other modifiers
The following modifiers can affect the validity of the triangulation 
data structure.

> 3. If not, is there a way to prevent the Delaunay triangulation from
> re-triangulating with the newly inserted vertex before other operations
> are created?

NA

> 4. What is the correct way to create new cells in a region with older ones?

I don't understand this question, but I hope/guess that my answers above 
will help for this one as well.

> 5. How do I know that I need to change orientation

Look at section 1 (Representation) in the User manual of 3D 
Triangulation Data Structure, the (non-geometric) notion of orientation 
is explained.

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