[geos-devel] Holes in holes

strk strk at keybit.net
Fri Nov 27 12:31:42 EST 2009

On Fri, Nov 27, 2009 at 02:47:17AM +0100, Frederik Ramm wrote:

> I have another remotely related question, that concerns the direction of 
> a polygon ring (CW or CCW). When I create a polygon with the 
> createPolygon factory method and pass it a number of rings, do I have to 
> take care that they spin in the right direction, or will GEOS make sure 
> that a correct polygon is created?

The createPolygon method takes an explicit shell and a list of holes.
You don't need to care about direction.

GEOS won't check validity automatic.
Use Geometry::isValid() if you want to check that.
Any ring direction is OGC valid.


 Free GIS & Flash consultant/developer      ()  ASCII Ribbon Campaign
 http://foo.keybit.net/~strk/services.html  /\  Keep it simple! 

More information about the geos-devel mailing list