On Tue, 3 Mar 2009, Frederik Ramm wrote:

>> I wrote this patch, so such ugly constructs are no longer needed and
>> should be removed from our data. So it is counter-productive to add
>> support for this "feature".
>
> If you define advanced multipolygons to allow this then it is no longer
> ugly but "specified behaviour" ;-) - but as I said, I'm not fond of
> touching rings either, it was someone else who stuffed that into the
> Wiki against my advice.

We need to separate two cases: Touching outer polygons should be 
considered ugly and if there is a outer style border running through the 
area --> Fine, looks a bit ugly, hopefully will get fixed :-)

Touching inner polygons are different. When I implemented inner polygons I 
thought that is not necessary, but creating e.g. the wood with beach and 
water inside without touching requires a very complicated way of tagging 
the ways (which BTW is not yet supported by JOSM, as JOSM uses every way 
once only). 3 different inner ways and 2 inner multipolygons compared to 2 
inner touching ways, so that from my point of view touching inner ways are 
a must have (if the have different features only).

>> I also would like to see the feature to handle
>> old style multipolygons removed (inner and outer with the same tags) as
>> this would provide an incentive to change these polygons to the new tagging
>> scheme.
>
> As map renderers, we have to educate mappers to do the right thing, but
> also we have to try to make the best maps from the material available. I

JOSM already warns about this old style construct and thus hopefully 
causes mappers to fix inner ways.

I wait for the day when both renderers implement the advanced 
multipolygons well and I can start warning about tagged outer ways :-)

> think that removing support for old-style polygons would be premature.
> We should also try to get not too far out of touch with Mapnik. The
> thing I hate most about multipolygons is the idea that certain rings
> need to be clockwise or counter-clockwise. This pops up every so often
> and I always say it is rubbish and then people produce some strange
> example where it really makes a difference ;-) I hope we've now got rid
> of these cases once and for all.

I did not even think about the direction of the ways. And Java also did 
not. Is there really a reason for way direction except for large 
structures like oceans (where you by definition cannot decide whats inner 
and outer otherwise)?

Ciao
-- 
http://www.dstoecker.eu/ (PGP key available)

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