#976: Voronoi polygons robustness issue ------------------------+--------------------------- Reporter: komzpa | Owner: geos-devel@… Type: defect | Status: new Priority: major | Milestone: Component: Default | Version: 3.6.2 Severity: Unassigned | Resolution: Keywords: | ------------------------+---------------------------
Comment (by mdavis): This is due to a couple of the generated Voronoi polygons being topologically invalid, and because of that failing during the intersection computation (when clipping the raw Voronoi polygons to a surrounding rectangle). The reason the polygons are invalid is that they contain two points which are almost identical, one of which happens to lie on another edge of the polygon, thus creating a self-intersection. The reason the very close points are present is because the input points (Voronoi sites) generating them lie on a regular grid pattern. This produces two Delaunay triangles with *almost* identical circumcentres. They are not 100% identical because of round-off error. The DT circumcentres form the vertices of the Voronoi polygons, and so polygons are created with almost-but-not-identical points in them. See attached diagrams for images. -- Ticket URL: <https://trac.osgeo.org/geos/ticket/976#comment:4> GEOS <http://trac.osgeo.org/geos> GEOS (Geometry Engine - Open Source) is a C++ port of the Java Topology Suite (JTS).
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