id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
10803,union algorithm returning invalid geometry,Volker Schöch <vschoech@…>,Barend Gehrels,"My ""_intPolygon"" type is actually a multi-polygon, using a polygon type that is based on '''int''', oriented '''counter-clockwise''' and '''open''' (not closed). Please consider the following example:
{{{
_intPolygon polygonA;
boost::geometry::read_wkt(""MULTIPOLYGON(((3174 1374,3174 2886,1374 2886,1374 2139,3174 1374)))"", polygonA); // does not throw
boost::geometry::correct(polygonA); // remove redundant closing point returned by wkt
boost::geometry::is_valid(polygonA); // returns true

_intPolygon polygonB;
boost::geometry::read_wkt(""MULTIPOLYGON(((1374 1092,1734 1092,3174 2526,3174 2886,1374 2886,1374 1092)))"", polygonB); // does not throw
boost::geometry::correct(polygonB); // remove redundant closing point returned by wkt
boost::geometry::is_valid(polygonB); // returns true

_intPolygon polygonC;
boost::geometry::union_(polygonA, polygonB, polygonC);
// polygonC = MULTIPOLYGON(((1374 809,1374 1092,1734 1092,3529 1718,3174 1374,3174 2526,3174 2886,1374 2886,1374 2139,1374 809)))
boost::geometry::is_valid(polygonC); // returns FALSE

boost::geometry::remove_spikes(polygonC);
// polygonC = MULTIPOLYGON(((1374 1092,1734 1092,3529 1718,3174 1374,3174 2526,3174 2886,1374 2886,1374 2139,1374 1092)))
boost::geometry::is_valid(polygonC); // still returns FALSE
}}}

May be related to #10661.[[BR]]
May be related to #9828.",Bugs,closed,Boost 1.60.0,geometry,Boost 1.57.0,Regression,fixed,"union, multi-polygon, polygon",