Holes of multipolygon relation not rendered #2082
Comments
Author: augustus.kling[at]gmail.com The islands within the lake are rendered by Mapnik for zoom level 11 or smaller. |
Author: steve8[at]mdx.ac.uk John - could you have a look at this one. Multipolygon relations boggle my mind. |
Author: Ldp I believe it currently renders fine and as expected? If agreed, this ticket can be closed. |
Author: augustus.kling[at]gmail.com You're right, the originally mentioned example looks great now. Unfortunately, I found another example where islands don't show up in Mapnik (but look fine in Osmarender and JOSM). See http://www.openstreetmap.org/?lat=47.87375&lon=9.83786&zoom=15&layers=B000FTF Cheers for looking into this. |
Author: steve8[at]mdx.ac.uk I have added natural=land to the three inner parts of the multipolygon for Rohrsee and it seems to have resolved it. This is the way I normally tag multipolygons, and I think tagging the inners is the key. |
Author: augustus.kling[at]gmail.com I don't agree that tagging the inner objects resolves the problem. It does fix the rendering, though.[[BR]] |
Author: mdk I think this problem is generally solved. Mapnik is normally leaving the holes in multipolygons empty. But sometimes it seams, that the mapnik DB is in an inconsistent state. This happens if there are several updates to to the MP and the inner/outer ways. In this case it could happend, that the holes are not correctly rendered. Only deleting and inserting ways and relation solf the problem for me (I run into this problem twice). But I can't tell you which opperations corruptede the mapnik DB. |
Author: joriskofman[at]gmail.com I have spotted this problem in some multipolygons located here: |
Author: Andy Allan As far as I'm aware, all multipolyon handling in osm2pgsql is working fine. If there are currently problems with multipolygons, that's the component to add new tickets to. |
Reporter: augustus.kling[at]gmail.com
[Submitted to the original trac issue database at 8.08am, Monday, 20th July 2009]
Mapnik does not render inner polygons of the multipolygon relation 172181. It consists of one outer polygon (26940083) tagged as natural=water and multiple inner polygons. The inner polygons are tagged as natural=wood and should be rendered as islands within the lake. Osmarender and JOSM are rendering the multipolygon correctly.
The holes (ways 23493419 and 23493421) in the nearby forest are rendered correctly in Mapnik, too.
Link to the area: http://www.openstreetmap.org/?lat=53.6127&lon=12.257&zoom=14&layers=0B00FTF
The direction of the inner polygons are differing. It seems that multipolygon relations are only rendered correctly if the outer polygon goes clockwise and the inner polygon goes counterclockwise. This behavior is documented in the English and German wiki-pages covering multipolygon relations. The wiki also clearly states that the directions of the polygons does not matter.
In the fixed issue #1113 it is said that the directions should be fixed during the osm2pgsql conversion process. This makes me wonder what causes the wrong rendering described above.
Does the polygon direction still matter for Mapnik?[[BR]]
If yes:[[BR]]
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