CGAL users discussion list

[Efi Fogel <>]

If a polygon has a duplicate vertex, then it is not simple. See the definition of "simple" polygons and "relatively simple" polygons in the manual and in particular the restrictions on polygons (Section 2.1).

BW, if you leave only poly1 and poly6 you still get the error.

   ____  _        ____             _
  /_____/_) o    /__________  __  //
 (____ (   (    (    (_/ (_/-(-'_(/
                         _/

On Tue, May 12, 2015 at 3:33 AM, Steven <> wrote:

Using CGAL 4.5.2. Below sample causes a bunch of precondition violations,
followed by an access violation exception. The funny thing is that if you
remove any of the 6 polygons from the input, everything runs fine. Why is
this happening?

The only unusual thing about the polygons that I can see is that poly6 has a
duplicate point - but it is not self-intersecting, only touching, so I
believe this shouldn't be a problem? And as said above, when you remove any
of the other polygons, this polygon can be handled just fine.

Is there a bug somewhere? Or is something wrong with my input?

------------

typedef CGAL::Exact_predicates_exact_constructions_kernel Knl;
typedef CGAL::Polygon_with_holes_2<Knl> Polygon_with_holes;
typedef CGAL::Polygon_2<Knl> Polygon;

int main(int argc, char* argv[])
{
        std::list<Polygon> polys;

        Polygon poly1;
        poly1.push_back(Point_2(417340.5, 523797.5));
        poly1.push_back(Point_2(419348.3269736591, 508552.92065337556));
        poly1.push_back(Point_2(421866.5, 489433.5));
        poly1.push_back(Point_2(421865.5, 489447.5));
        poly1.push_back(Point_2(417342.43500051671, 523783.40213909268));
        poly1.push_back(Point_2(417341.5, 523790.5));
        polys.push_back(poly1);

        Polygon poly2;
        poly2.push_back(Point_2(417342.43500051671, 523783.40213909268));
        poly2.push_back(Point_2(421865.5, 489447.5));
        poly2.push_back(Point_2(421837.5, 489724.5));
        poly2.push_back(Point_2(417365.15018218826, 523612.759577192));
        poly2.push_back(Point_2(417347.5, 523746.5));
        poly2.push_back(Point_2(417346.5, 523753.5));
        poly2.push_back(Point_2(417344, 523772));
        poly2.push_back(Point_2(417342.74397163116, 523781.15106382978));
        polys.push_back(poly2);

        Polygon poly3;
        poly3.push_back(Point_2(421837.5, 489724.5));
        poly3.push_back(Point_2(421832.5, 489771.5));
        poly3.push_back(Point_2(421831.5, 489780.5));
        poly3.push_back(Point_2(417365.84675276978, 523607.52457525046));
        polys.push_back(poly3);

        Polygon poly4;
        poly4.push_back(Point_2(421831.5, 489780.5));
        poly4.push_back(Point_2(421830.5, 489794.5));
        poly4.push_back(Point_2(417366.29927861993, 523604.12366546877));
        polys.push_back(poly4);

        Polygon poly5;
        poly5.push_back(Point_2(417322.5, 523931.5));
        poly5.push_back(Point_2(417318.5, 523966.5));
        poly5.push_back(Point_2(417317.5, 523968.5));
        polys.push_back(poly5);

        Polygon poly6;
        poly6.push_back(Point_2(417344, 523772));
        poly6.push_back(Point_2(417346.5, 523753.5));
        poly6.push_back(Point_2(417346.72222222225, 523752.16666666663));
        poly6.push_back(Point_2(417347.5, 523746.5));
        poly6.push_back(Point_2(417366.29927861993, 523604.12366546877));
        poly6.push_back(Point_2(421830.5, 489794.5));
        poly6.push_back(Point_2(421802.5, 490071.5));
        poly6.push_back(Point_2(417411.35391183395, 523265.52037297864));
        poly6.push_back(Point_2(417359.5, 523657.5));
        poly6.push_back(Point_2(417358.5, 523664.5));
        poly6.push_back(Point_2(417355.28571428568, 523688.92857142852));
        poly6.push_back(Point_2(417353.5, 523702.5));
        poly6.push_back(Point_2(417352.5, 523709.5));
        poly6.push_back(Point_2(417347.5, 523746.5));
        poly6.push_back(Point_2(417347.5, 523747.5));
        poly6.push_back(Point_2(417346.72222222225, 523752.16666666663));
        poly6.push_back(Point_2(417346.33333333337, 523755));
        polys.push_back(poly6);

        list<Polygon_with_holes> polyHoles;
        CGAL::join(polys.begin(), polys.end(),
std::back_inserter(polyHoles));
}



--
View this message in context: http://cgal-discuss.949826.n4.nabble.com/Why-does-this-set-of-polygons-cause-CGAL-join-to-crash-tp4660815.html
Sent from the cgal-discuss mailing list archive at Nabble.com.

--
You are currently subscribed to cgal-discuss.
To unsubscribe or access the archives, go to
https://sympa.inria.fr/sympa/info/cgal-discuss