CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Does one of you mesh has a boundary?

The list of PRs that could have introduced a regression is here:
https://github.com/CGAL/cgal/pulls?utf8=%E2%9C%93&q=is%3Apr+is%3Aclosed+label%3AMerged_in_4.12.2++label%3APkg%3A%3APMP+

I don't see anything suspicious. Is it deterministic?

Best,

Sebastien.



On 2/4/20 11:59 PM, Giles Puckett wrote:
> Bonjour,
>
> I have a CAD program that uses PMP to merge meshes. I moved from 4.12 to 
> 5.0 in order to use the default visitor to keep attributes on faces 
> through surface mesh unions. However, some previously working meshes now 
> fail with an infinite loop. The problem also appears on 4.14.2.
>
> The infinite loop is in Corefinement::remove_unused_polylines at 
> face_graph_utils.h, line 1634: (in 5.0)
>
> for(vertex_descriptor v: vertices_kept)
>    {
>      halfedge_descriptor h = halfedge(v, tm), start=GT::null_halfedge();
>
>      do{
>        while ( !is_border(h, tm) || is_border(opposite(h, tm), tm) ) // 
> This while loop never exits
>          h = opposite(next(h, tm), tm);
>        halfedge_descriptor in = h;
>        if (start==GT::null_halfedge())
>          start=in;
>        else
>          if (start==in)
>            break;
>        while ( is_border(h, tm) )
>          h = opposite(next(h, tm), tm);
>        set_next(in, opposite(h, tm), tm);
>      }
>      while(true);//this loop handles non-manifold vertices
>    }
>
> One mesh is a simple convex shape, the other is the result of a previous 
> union. All unions are done with exact predicates and constructions in 
> the standard way for consecutive bool ops. Testing for 
> self-intersections before and during the union reveals nothing.
>
> Sadly, I cannot reproduce it in a simple test example program (when 
> writing the meshes to OFF file, precision is lost, and I get 
> self-intersections or an assertion about collinear points). I suspect 
> there may be zero-area triangles produced by the first union.
>
> Three questions:
>
> Have there been any changes in corefinement, PMP or surface meshes 
> between 4.12 and 4.14.2 that might produce this, or any known regressions?
> And is there any way I can write the meshes out with sufficient accuracy 
> to submit a simple test case?
> Lastly, is there any way I can get the functionality of the example 
> program (corefinement_mesh_union_with_attributes) to work in 4.12?
>
> Thanks for any help and for reading on this far :-)
>
> Giles.