[Boost-bugs] [Boost C++ Libraries] #12355: False self intersection

Subject: [Boost-bugs] [Boost C++ Libraries] #12355: False self intersection
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-07-27 15:00:08

#12355: False self intersection
------------------------------+---------------------------
 Reporter:  jan.kleemann@…    |      Owner:  barendgehrels
     Type:  Bugs              |     Status:  new
Milestone:  To Be Determined  |  Component:  geometry
  Version:  Boost 1.61.0      |   Severity:  Problem
 Keywords:                    |
------------------------------+---------------------------
 Please see the following code:

 {{{
 #include <boost/geometry.hpp>
 #include <boost/geometry/geometries/point_xy.hpp>
 #include <boost/geometry/geometries/polygon.hpp>

 using namespace boost::geometry;

 typedef double FloatType;
 typedef model::d2::point_xy<FloatType> Point;
 typedef model::polygon<Point> Polygon;
 typedef model::multi_polygon<Polygon> MultiPolygon;
 typedef model::ring<Point> Ring;
 typedef model::box<Point> Box;
 typedef model::linestring<Point> LineString;


 int main(int argc, char *argv[])
 {
    using namespace std;

    Polygon p1;
    boost::geometry::read_wkt("POLYGON((440408.69120520249
 5684415.5176829416,"
                                       "440376.96050000004
 5684329.5744000003,"
                                       "440376.93154344801
 5684329.5945822615,"
                                       "440408.69005920028
 5684415.5145825278,"
                                       "440408.69120520249
 5684415.5176829416))", p1);

    std::string err;
    bool valid = boost::geometry::is_valid(p1, err);
    cout << "is_valid(p1): " << (valid?"true":"false") << ":\n" << err <<
 endl;

    Polygon p2;
    boost::geometry::read_wkt("POLYGON(("
                              "440408.83723096416 5684415.9121634094,"
                              "440421.56219999958 5684410.6604999993,"
                              "440423.30049999990 5684412.0036999993,"
                              "440439.33189999964 5684394.8839999996,"
                              "440423.75960000046 5684357.4199000001,"
                              "440420.99959999975 5684350.7814000007,"
                              "440404.12129999977 5684310.1740000006,"
                              "440393.24469999969 5684317.6517999992,"
                              "440377.49349999987 5684329.2028999999,"
                              "440376.96050000004 5684329.5744000003,"
                              "440408.69005920028 5684415.5145825278,"
                              "440408.69120520249 5684415.5176829416,"
                              "440408.83689894457 5684415.9118452258,"
                              "440408.83723096416 5684415.9121634094))",
 p2);

    MultiPolygon mp;
    union_(p1, p2, mp);
    cout << "mp: " << boost::geometry::wkt(mp) << endl;


    return 0;
 }
 }}}

 Output:
 {{{
 is_valid(p1): false:
 Geometry has invalid self-intersections. A self-intersection point was
 found at (440409, 5.68442e+006); method: i; operations: i/u; segment IDs
 {source, multi,
 ring, segment}: {0, -1, -1, 0}/{0, -1, -1, 2}
 mp: MULTIPOLYGON(((440409 5.68442e+006,440409 5.68442e+006,440377
 5.68433e+006,440409 5.68442e+006)))
 }}}

 Both polygons (p1 and p2) are in fact valid, without any self-
 intersections. But boost.geometry sees one and can't union the two
 polygons correctly.

 Thank you, for the good work.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12355>
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