CGAL users discussion list

[Guillaume Damiand <>]

Splitting edges or vertices will introduce new vertices, however my requirment is just connecting the vertices on the two rings without introducing any new vertices.

Besides, the two rings are disconnected to each other, how to build a halfedge connecting them at the first beginning please? If this could be done, then i believe the following connection operations can be implemented by using the functions such as split_vertex, split_edge and so on.

Thanks!

This is not possible. By definition of half-edge data structure you can only connect couple of half-edges. Thus if your two cycles do not have the same number of half-edges, you can
1) add half-edges on the smaller cycle by using split-edge (or symmetrically remove some half-edges of the bigger cycle);
2) or create a new facet connected to the smaller one such that the boundary of the two facets has the same number of half-edges than the second facet, then you can connect the two components.

Guillaume

On Sat, Feb 19, 2011 at 12:30 AM, Sebastien Loriot (GeometryFactory) <sloriot.ml@gmail.com> wrote:

wrote:

Hi everyone, I now have a problem as follows:
I have two rings of vertices (halfedges) with different degrees (number of
edges), each ring can be seen as a hole, which means the halfedges on each ring
are border edges. Now i want to merge the two rings with some algorithm, how to
use the functions in  Polyhedron_3, for example split_edge,join_facet..., to
connect the vertices on the two rings one by one, in order to finish this task
please?

Have you tried splitting some edges in the loop having the less boundary
halfedges (see split_vertex and split_edge)?

http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Polyhedron_ref/Class_Polyhedron_3.html

Actually, this problem can be explained as: how to do the "join_loop" operation
in Polyhedron_3 when the degrees of the two facets are different? I know the
rule of how to connect the vertices on the two rings gradually, and just don't
know how to do it through the functions provided in Polyhedron_3, since the two
rings are diconnected to each other at first.

Meanwhile, I just want to use the operations in Polyhedron_3 without rebuilding
the whole mesh using the "delegate " method or Nef_polyhedron.

Could you please help me? Thanks!

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