CGAL users discussion list

["Eric A. Perlman" <>]

I noticed several of the algorithms (such as Polygon/Polygon
intersection) require that each polygon have a counter-clockwise
orientation. 

 Polygon_2 poly(...);
 if (poly.orientation() == CGAL::CLOCKWISE)
   poly.reverse_orientation(); 

I hope this helps, I am also new to CGAL,
  -- Eric


On Wed, Mar 12, 2008 at 01:39:49PM +0300, Boris Kazakov wrote:
> Hi, I'm new to CGAL and I'd like to do the following:
>    Create a new Triangulation_2
>    Add several points to it(for example, (0,0), (10,0), (10,10), 
> (0,10),(5,5))
>    Then move central point somewhere and check, weather the 
> triangulation remains valid(by calling is_valid() method)
>  
> When I am moving central point outside of the box [0,0,10,10]  I get the 
> following error:
> 
> CGAL error: assertion violation!
> Expr: s == LEFT_TURN
> File: /usr/local/include/CGAL/Triangulation_2.h
> Line: 633
> 
> Is there a way to disable this assertion  violation, so that after 
> moving the point is_valid method will return false?
> 
> Thanks,
> 
> Best regards.
> 
> 
> 
>   
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