id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
13522	Invalid empty result using boost::geometry::difference	lehnert@…	Barend Gehrels	"Hello,

executing the following polygon difference operation sequence produces an obviously incorrect empty result. The first difference produces a (possibliy) valid result with a spike which might be the actual problem. The third difference with the previous result generates an empty result. The intermediate difference is required the reproduce this behaviour. Without it the result of the third difference is correct. Removing the spike from step one also solves the problem.

Code to reproduce this:

using point_type = boost::geometry::model::d2::point_xy<double>; using polygon = boost::geometry::model::polygon<point_type>; using multi_polygon = boost::geometry::model::multi_polygon<polygon>; 

    BoostGeometryBridge::Polygon2d_t Right[3];
    BoostGeometryBridge::MultiPolygon2d_t Left[4];

    boost::geometry::read_wkt(""MULTIPOLYGON(((0.747399249902131135 -0.974867609298678328,0.744720465461241043 -0.984866128861542012,0.737400169703072983 -0.992186849248596014,0.72740024741975795 -0.994866631198703,0.169444950081761997 -0.994882813404528998,0.156263880981993009 -0.992649068186161054,0.144555091741144004 -0.986196591543298973,0.135626528763234999 -0.976246166252738967,0.0970341390445131069 -0.91515608670535098,0.0527935015388215009 -0.831873652851741974,0.0149278636239085008 -0.745505885364162957,-0.016349202846282801 -0.656539920475841976,-0.0408612872409169006 -0.56547754891590496,-0.0584701351532070993 -0.472832385681689005,-0.0690764281904878985 -0.379126973119241983,-0.0726203441553292944 -0.284889833651171986,-0.0690818944579700972 -0.19065248877542601,-0.058481036857029399 -0.0969464611485150035,-0.0408775628926898033 -0.00430027666216776031,-0.0163707606471800993 0.086763516577464006,0.0149011452653820004 0.17573129555438699,0.0527617733210207981 0.262101259307556012,0.0969975799226773933 0.345386259216249991,0.135586426022915013 0.406478577227274984,0.144514411807557003 0.416429520405822984,0.156222826750318011 0.422882676210660002,0.169403766258661992 0.42511718599825099,0.727359063596658029 0.425133368204076989,0.737359141304932963 0.422454166307816015,0.744679861691986966 0.415133870549649009,0.747359067455327319 0.405136098375181386,0.747329770868999987 1.43513394783313997,2.74732976755064007 1.43524915817017007,2.74708725756255978 5.64524915118547987,-2.74750006237453981 1.25999999251885009,-2.74749997944197011 -4.43500000748115042,0.747500020558034994 -4.43500000604748035,0.747399249902131135 -0.974867609298678328),(-2.49638915854706989 0.152811596222504009,-1.75719536363572004 1.80498971421238008,-1.01782283569549992 1.4741902811305001,-1.75234596398119002 -0.167548384003570999,-1.76762179055725999 -0.173243028570225999,-2.49638915854706989 0.152811596222504009)))"", Left[0]);

    boost::geometry::read_wkt(""POLYGON((-1.57590744074229994 2.19505211912179998,-2.74750006237453981 1.25999999251885009,-2.74750004134586989 -0.184043917378418992,-1.76796680349592994 -0.184043903114115004,-1.74492840055212994 -0.175455463366190001,-1.00461083616106994 1.47923439340570995,-1.57590744074229994 2.19505211912179998))"", Right[0]);
    boost::geometry::read_wkt(""POLYGON((2.74708725756255001 5.64524915118547987, 1.48149582377297007 4.63517624723808019, 2.7471454369183701 4.6352491528611397, 2.74708725756255001 5.64524915118547987))"", Right[1]);
    boost::geometry::read_wkt(""POLYGON((-2.74749997944197011 -4.43500000748115042, -2.74750006237453981 1.25999999251885009, -3.11250006493298015 1.43568817247817004, -3.11249997689355018 -4.61000000763086959, -2.74749997944197011 -4.43500000748115042))"", Right[2]);

    for(int i = 0; i < 3; i++)
    {
      boost::geometry::difference(Left[i], Right[i], Left[i + 1]);
    }

Final result in Left[3] is empty.


"	Bugs	assigned	To Be Determined	geometry	Boost 1.66.0	Problem		geometry difference	henrik@…