CGAL users discussion list

[Francesc Vila <>]

El 21/06/2010 18:23, Sebastien Loriot (GeometryFactory) escribió:
> Francesc Vila wrote:
> > El 21/06/2010 17:44, Sebastien Loriot (GeometryFactory) escribió:
> > > Francesc Vila wrote:
> > > > Hi all,
> > > >
> > > > I am using CGAL to make some transformations on a GDSII (stream 
> > > > format) file. Within this file, I can read polygons that aren't 
> > > > always simple. Is there any way to partition a polygon that is not 
> > > > simple? In fact, the polygon is weakly simple (has a coincident edge).
> > > >
> > > > Thanks in advance,
> > > >
> > > > Francesc Vila
> > >
> > > I think you will need to use a pre-processing step to extract simple 
> > > polygons from each weakly simple polygon.
> > >
> > > S.
> > I thought so..... :(
> >
> > Further reading this list, I found a method to create polygons with 
> > holes from Polygon_2. But it is dated 2009 and the code doesn't 
> > compile on my system.... Maybe it is my fault, but I think I can 
> > benefit from the general idea it implements.
> >
> > Regards,
> >
> > Francesc Vila
> An alternative that may fit you need is to use a constrained
> triangulation to partition your weakly simple polygon,
> constraints being polygon edges.
>
> S.
Hi,

I tried the constrained triangulation, but some of the triangles it 
generated were part of the hole and not the polygon. Finally I 
preprocessed the polygon to make it simple. I have iterated through all 
vertices, and once I find a repeated one, I create a new polygon and 
save into a list. When I have finished I join all polygons in that list 
to obtain the polygon with holes.

Best regards,

Francesc