[OSM-talk] Complex multipolygon not rendering

[Michael]

Hi everyone,

recently I stumbled across a pretty complex relation [1] which is not 
rendered correctly.

Looking into it I found that JOSM reported some validation errors. So I 
thought those caused the problems and so I fixed the geometry until JOSM 
was happy. But obviously this did not solve the issues since the 
rendering still is not really what one would expect. At least on zoom 
level 14 some patches render fine while others are still broken ([2]).

I assume that this might be due to the specific geometry of the 
multipolygon. Especially there are many rings touching in one or two 
single points. There is a page on the wiki [3] discussing the validity 
of this geometry. So this seems to be a critical geometry.

So in the end I am still not sure if this relation is actually beyond 
the capability of the rendering or if there is simply something wrong 
with the multipolygon.

Thanks,
Michael

[1] http://www.openstreetmap.org/relation/1284003
[2] http://www.openstreetmap.org/relation/1284003#map=14/42.0100/-120.7526
[3] http://wiki.openstreetmap.org/wiki/Relation:multipolygon/validity