|
|
Geometry : |
Subject: [geometry] difference algorithm returning invalid geometry
From: Volker Schöch (vschoech_at_[hidden])
Date: 2014-10-14 05:54:34
I am about to file this as a bug report, but given the discussion here I think it makes sense to have someone review the issue first.
My "polygon" type is actually a multi-polygon. It is oriented counter-clockwise and not closed, my point type is based on int.
_intPolygon polygonA;
boost::geometry::read_wkt("MULTIPOLYGON(((1701 985,3501 985,3501 2785,1701 2785,1701 985)))", polygonA); // does not throw
boost::geometry::is_valid(polygonA); // returns true
_intPolygon polygonB;
boost::geometry::read_wkt("MULTIPOLYGON(((1698 1860,1698 1122,2598 1392,3492 1842,3492 32706,2598 2340,1698 1860)))", polygonB); // does not throw
boost::geometry::is_valid(polygonB); // returns true
_intPolygon polygonC;
boost::geometry::difference(polygonA, polygonB, polygonC); // does not throw
// polygonC == MULTIPOLYGON(((1701 1122,1701 985,3501 985,3501 2785,3492 1857,3492 1842,2598 1392,1701 1122)),((1701 1861,2598 2340,1669 2785,1701 2785,1701 1861)))
boost::geometry::is_valid(polygonC); // returns false!
_intPolygon polygonD;
boost::geometry::read_wkt("MULTIPOLYGON(((1698 2772,1698 1860,2598 2340,3492 2412,3492 32743,1698 2772)))", polygonD); // does not throw
boost::geometry::is_valid(polygonD); // returns true
_intPolygon polygonE;
boost::geometry::difference(polygonC, polygonD, polygonE); // throws "Boost.Geometry Overlay invalid input exception"!
Any suggestions or comments are greatly appreciated.
Thanks
Volker