CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 11/14/2012 12:32 PM, Shriramana Sharma wrote:
> Hello and thanks for your reply.
>
> On Tue, Nov 13, 2012 at 1:12 PM, Efi 
> Fogel<>
>   wrote:
> > If the input does not comply with the precondition, that is, the input
> > polygons are invalid according to the specification in the manual, the
> > results are nondeterministic.
>
> Well that is what I was asking, wasn't I? I asked in a previous mail
> in this thread:
>
> """Or is it just that for "invalid" polygons the output is undefined, and
> maybe sometimes right and sometimes wrong?"""
>
> IMHO it should be mentioned in the documentation that for invalid
> polygons, proper results of operations cannot be expected.

It's already there:
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Boolean_set_operations_2/Chapter_main.html#Subsection_19.2.1
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Boolean_set_operations_2/Chapter_main.html#Subsection_19.2.2


> > The program may halt and output wrong results or run forever, who cares, at
> > least I don't. It's not worth it.
>
> Fine, but I can always check for the orientation and reverse it using
> functions that CGAL itself provides, right? It's just that you guys
> don't do it by default because it can be costly (and perhaps not what
> the user intended to happen), right?
Correct.


Sebastien.