[geos-devel] [GEOS] #995: Voronoi diagram fails when the points are from the ring of a circle

[GEOS]

#995: Voronoi diagram fails when the points are from the ring of a circle
------------------------+--------------------------
 Reporter:  ajolma      |      Owner:  geos-devel@…
     Type:  defect      |     Status:  new
 Priority:  major       |  Milestone:
Component:  Default     |    Version:  3.6.2
 Severity:  Unassigned  |   Keywords:
------------------------+--------------------------
 I have a set of points from the ring of a circle. If I select all or
 almost all of them for voronoi diagram computation, it fails with

 {{{
 GEOSVoronoiDiagram: TopologyException: Input geom 1 is invalid: Self-
 intersection at or near point 360736.47000001703 7127320.700000016 at
 360736.47000001703 7127320.700000016
 }}}

 There is a clear boundary where the error happens (I'm using PostGIS),
 this fails:

 {{{
 SELECT ST_VoronoiPolygons(geom) As geom
 FROM (SELECT st_collect(geom) as geom from s where i < 248) As g;
 }}}

 but this does not fail:

 {{{
 SELECT ST_VoronoiPolygons(geom) As geom
 FROM (SELECT st_collect(geom) as geom from s where i < 247) As g;
 }}}

 Versions are
 {{{
 POSTGIS="3.0.0dev r17356" [EXTENSION] PGSQL="100"
 GEOS="3.8.0rc2-CAPI-1.13.1 " PROJ="Rel. 5.2.0, September 15th, 2018"
 LIBXML="2.9.4" LIBJSON="0.12.1" LIBPROTOBUF="1.2.1"
 }}}

-- 
Ticket URL: <https://trac.osgeo.org/geos/ticket/995>
GEOS <http://trac.osgeo.org/geos>
GEOS (Geometry Engine - Open Source) is a C++ port of the Java Topology Suite (JTS).