CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Vertex handles inserted will remain valid in both scenarios
(refine_Delaunay_mesh_2 is using Delaunay_mesher_2 internally).
About the process, you can create your domain, insert your fixed points
and then only once the mesher.

Sebastien.

On 02/10/2016 10:52 AM, rytis wrote:
> Hello,
>
> I am a beginner with CGAL which I like very much so far. I think there
> is an issue (of documentation) with constrained Delaunay triangulation.
> The issue is below, but first, I want to describe the problem. If
> someone could indicate how solve my indexation problem, that would be
> nice too!
>
> Problem:
> I need to create a 2d mesh from "thin air" + boundaries (as if by
> Delaunay_mesher_2) but I must insert a few points which remain constant
> (that don't disappear or change their coordinates -- as if they were
> "punctual" constraints).
>
>
> Issue:
> Is it correct that,
> A) refine_Delaunay_mesh_2 takes vertices as constants, so that, in
> particular, vertex_handles remain valid throughout the refinement
> procedure, and that no new vertices are added, whereas
> B) Delaunay_mesher_2 invalidates vertex_handles, by possibly adding
> and/or removing some of them in the process of refinement?
>
> So far this is what I tried to solve my problem:
>
> 1: insert boundary nodes and set boundary constraints,
> 2: run B) to generate a "new" triangulation
> 3: insert my "custom" vertices,
> 4: run A) (expecting that vertices remain constant)
>
> I have to generate two types of output for nodes and links, respectively
> ID,x,y
> ...
>
> ID,ID
> ...
>
> For that, I keep vertex handles in a map like this:
> map<string,Vertex_handle> node_map;
>
> this map is updated  after each step like so:
> node_map[ID]=Vertex_handle(Vertex_iterator);
>
> which allows the retrieval of the vertex coordinates by their ID.
>
> I noticed that during step 4 some of the vertex handles were not matched
> by an ID which makes me think that A) is incorrect (Help!) I checked
> that those vertices inserted at step 3 were still present though (Help....)
>
> Thanks,
> Rytis