id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
13566	difference and intersection yield wrong result	Henrik Zimmer <henrik@…>	Barend Gehrels	"We are developing new algorithm that will hopefully be based on boost::geometry. Unfortunately we have come across some errors in the difference and intersection computations (possibly related to #13522 and #13553), which are a central part of the algorithm.

I posted my original problem as a comment in #13522 (https://wandbox.org/permlink/ThHHAW13DOdHbgEx)

After reading #13553 I tried out the define BOOST_GEOMETRY_NO_ROBUSTNESS which at first seemed to work. However, I then ran into a problem at another position (https://wandbox.org/permlink/8YH8EiIRMtsUd1LH)
The two polygons have finite, not too small intersection, but both the intersection and the difference are empty.

The problem seems be that the two geometries overlap almost exactly in one vertex (0.0054, -0.02436) - this is the second vertex of the green polygon and the first vertex of the blue polygon.

Changing the coordinate (0.0054) in the green polygon only slightly yields the correct result.

"	Bugs	new	To Be Determined	geometry	Boost 1.66.0	Showstopper			henrik@…