CGAL users discussion list

[Renato Espírito Basso Poli <>]

Hi Laurent,

I am still struggling on this one. 

Is it possible to avoid edge splitting of _some_ constrained edges only?

Thanks

Renato

Em sex, 20 de set de 2019 16:23, Renato Espírito Basso Poli <> escreveu:

Hi Laurent,

Thanks, it is exactly what I needed and it is working fine.

(But)

In the next step of my project, I need to refine freely "some" of the constrained edges, but not others.

Can you see a way to select which constrained edges to _lock_ the refinement?

Perhaps some tweaks in "refine_Delaunay_mesh_2_without_edge_refinement"?

rgds,

Renato

Em qua, 11 de set de 2019 às 03:35, Laurent Rineau (CGAL/GeometryFactory) <> escreveu:

On Tuesday, September 10, 2019 8:39:37 PM CEST Renato Poli wrote:
> Hi Sebastien,
>
> I worked the past days on simplifying my problem and trying to understand
> what is going on.
> I made a very raw code (below) as an example.
>
> Please find attached three pictures:
> (1) the mesh without refinement
> <http://cgal-discuss.949826.n4.nabble.com/file/t376144/cgal-mesh1.png>
>
> (2) the refined mesh after
> / typedef CGAL::Delaunay_mesh_size_criteria_2<CDT> Criteria;
>      CGAL::refine_Delaunay_mesh_2(cdt,seeds.begin(), seeds.end(),
> Criteria(0, 100));/
> <http://cgal-discuss.949826.n4.nabble.com/file/t376144/cgal-mesh2.png>
>
> (3) the seed location (the extra point when compared to mesh1)
> <http://cgal-discuss.949826.n4.nabble.com/file/t376144/cgal-mesh3.png>
>
> I dont understand
>      (i) why the refiner changes the mesh beyond the shape and size
> criteria? ; and

Hi Renato,

Even without any mesh criteria on faces, the algorithm starts by inserting
points on constrained edges to ensures that all sub-edges have the Gabriel
property (empty circumscribed circle).

>      (ii) why the mesh refiner changes the area with a seed?
>
> Is there any way to avoid those points and get more 'control' on the
> meshing?

The seeds control insertion of points inside the regions, and not on the
border of it.

There is an undocumented header file in CGAL:

  <CGAL/Delaunay_mesher_no_edge_refinement_2.h>

It has a function `refine_Delaunay_mesh_2_without_edge_refinement` that you
could use to mesh the region without touching at all at the constrained edges.
That might suit your needs.


Best regards,

Laurent

--
Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/




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