Opened 6 years ago

Closed 6 years ago

Last modified 6 years ago

#7462 closed Bugs (fixed)

geometry::union_ yields degenerated results

Reported by: Danvil <danvil@…> Owned by: Barend Gehrels
Milestone: To Be Determined Component: geometry
Version: Boost 1.48.0 Severity: Problem
Keywords: Cc:


The following data gives wrong results with geometry::union.

float data1[][2] = {{0,0}, {-0.3681253195,0.9297761917}, {2.421203136,2.034152031}, {2.789328575,1.104375958}, {0,0}};
float data2[][2] = {{2.76143527,1.093332171}, {2.076887131,1.822299719}, {4.263789177,3.875944376}, {4.948337555,3.146976948}, {2.76143527,1.093332171}};

polygon_t p1, p2;
boost::geometry::append(p1, data1);
boost::geometry::append(p2, data2);

std::vector<polygon_t> output;
boost::geometry::union_(p1, p2, output);

Please find attached the whole main file and program output.

Attachments (2)

boost_geometry_union_bug.cpp (1.3 KB) - added by Danvil <danvil@…> 6 years ago.
boost_geometry_union_bug_output.txt (431 bytes) - added by Danvil <danvil@…> 6 years ago.

Download all attachments as: .zip

Change History (6)

Changed 6 years ago by Danvil <danvil@…>

Changed 6 years ago by Danvil <danvil@…>

comment:1 Changed 6 years ago by Danvil <danvil@…>

Actually union(p1,p2) yields a degenerated polygon while union(p2,p1) gives the correct result. In my use case, wrong results occur in ~0.5% of the cases.

comment:2 Changed 6 years ago by Barend Gehrels

Resolution: fixed
Status: newclosed

(In [83481]) [geometry] Fix ticket 7462, degenerate union for float. This was caused by two distances being wrong (by floating point precision). We now use earlier the alternative sort method (sorting on left/right), using relaxed_epsilon. This fixes the cause.

comment:3 Changed 6 years ago by Barend Gehrels

(In [83482]) [geometry] Fix ticket 7462, (unit tests)

comment:4 in reply to:  3 Changed 6 years ago by anonymous

Replying to barendgehrels:

(In [83482]) [geometry] Fix ticket 7462, (unit tests)

Thanks for fixing this!

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