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Polygon clipping issues #3
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@hjanetzek - great, thanks, I'll have a look. Do you have a screenshot with broken polygons ? |
most of these wrong points were not visible because the 'stencil buffer method' for polygon drawing can cope it. e.g. tile: 17/68736/42655 the building at top center [1]http://city.informatik.uni-bremen.de/~jeff/screenshots/Screenshot_2013-01-14-13-30-47.png Clipper produces [1]http://city.informatik.uni-bremen.de/~jeff/screenshots/Screenshot_2013-01-14-14-13-33.png another one where clipping fill the tile with water (behind residential) I had a few more really results that I cannot find atm where complex landuse polygons should result in one tile filling quad but were made of 9 points. |
btw. the problem with drawing all objects for one layer (by tag) in one go via stencil buffer is that overallping parts will cancel each other out.. just in case that you see it and wonder whats goind on. |
It seems that the default agg polygon clipper is not reliable when it is used for geometry output, as stated on their site. I tried to figure out what might cause the broken polygons when using this backend in VectorTileMap and found that the clipping messes things up. I've hacked Clipper into polygon processing and it seems to do the job well. the results is in my 'origin' branch. maybe you can integrate it properly :)
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