[OSM-dev] Advice sought on polygon-with-hole drawing

Frederik Ramm frederik at remote.org
Fri Mar 14 01:03:02 GMT 2008


Hi,

> I think we should stick with the evenodd rule. It is not that difficult
> for users when editing - colour on the right, it is neccesary for
> coastlines, and there is nothing to gain by making it unneccesary. If
> some renderers don't need the rule, it's going to be much harder to tell
> people they are wrong when the draw things the wrong way round.

I think coastlines are really a big exception and everybody can
understand that. 

If we have proper "inner" and "outer" roles, direction of the ways is
not required for computing and simply requiring it to make people into
better coastline mappers seems a bit over the top to me.

The logical consequence of your above statement would be that we
should drop rendering of simple areas (without holes) unless they're
drawn clockwise!

Also, my idea would allow a way to serve as an "inner" member of one
multipoly at the same time as as an "outer" member of another; I think
you couldn't get that with evenodd. 

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00.09' E008°23.33'





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