CGAL users discussion list

[Andreas Fabri <>]

 wrote:
> Dear all,
>
> Is there any way to reverse the orientation of a single face (given by a 
> halfedge handle) in a polygonal mesh?
>
> Now I know how to reverse the orientaions of all faces. This can be achieved 
> by calling:
> void Polyhedron_3<..>.inside_out ()  ------ reverses facet orientations
>
> How do I deal with a single face?

Hi Kevin,

What would be the meaning of this?  Faces must be oriented in a consistent
way, that is two faces sharing an edge, must be  hooked up with two
opposite halfedges. So the orientation of one face implies the orientation
of the neighbor faces, and changing the orientation of one face, does
not really make sense.

What you can do is have an adapter layer, add a boolean flag to your Face 
type,
and write an iterator adaptor that when you call operator++ for a halfedge
circulator internally calls operator--

andreas