[OSM-dev] 0.6

Martijn van Oosterhout kleptog at gmail.com
Tue May 6 22:53:16 BST 2008

On Tue, May 6, 2008 at 10:34 PM, Iván Sánchez Ortega
<ivan at sanchezortega.es> wrote:
>  Namely, that the inner hulls (rings) of a multipolygon must have the inverse
>  direction of the outer hull (ring), or else some renderers will bork up the
>  result. See:

I keep hearing that assertion but no evidence. At least Mapnik should
have no problem. If there is a problem it's a bug that should be
fixed. Or at the very least *documented*.

>  http://wiki.openstreetmap.org/index.php/Relations/Multipolygon

This also provides no details about the problem to be solved. Even the
clockwiseness is mentioned only as a "may be useful".

Given a set of closed rings that don't cross you can unambiguously
draw a polygon with it. Computer are very good at working out such
details. People on the other hand, are not. Ergo, let the people draw
the shapes and let the computers sort out the drawing.

Have a nice day,
Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/

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