CGAL users discussion list

["Ch'Gans" <>]

On 8 April 2017 at 08:36, Efi Fogel 
<>
 wrote:
> If you are using an exact predicate and exact construction kernel, then it
> seems like a bug; either in the union operation (join) or the validity
> check.

I am using Epeck, so there's either a bug in my code, in the
validation or in the set.
I have tried to build a use case that show the problem without having
to insert thousands of polygons.
So far the simplest use case i found requires to insert ca. 100 circles.
Next step is to serialise these circles and write a simple program to
read them back and insert them into a set, if the problem is still
there, then i will open a ticket on github with the data file and the
simple program.

Chris

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> On 7 April 2017 at 04:51, Ch'Gans 
> <>
>  wrote:
>>
>> Hi there,
>>
>> Every now and then when I join polygons into a polygon set, the
>> polygon set becomes invalid.
>>
>> To make sure i am not inserting invalid polygon, i have tried to check
>> them all individually before calling join(), eg:
>>
>> std::vector<Polygon_2> allPolygons;
>> buildPolygons(allPolygons);
>> Polygon_set_2 S;
>> for (const auto &poly: allPolygons)
>>    if (!CGAL::is_valid_unknown_polygon(poly, S.traits()))
>>      qWarning() << "Found invalid input polygon";
>> S.join(allPolygons.begin(), allPolygons.end());
>> if (!S.is_valid()) {
>>   qDebug() << "Polygon set invalid after inserting all polygons";
>> }
>>
>> When i run the above code, i get no "Found invalid input polygon"
>> warning, yet i get a final "Polygon set invalid after inserting all
>> polygons" along with this CGAL message:
>>
>> CGAL warning: check violation!
>> Expression : false
>> File : /usr/include/CGAL/Arrangement_2/Arrangement_on_surface_2_global.h
>> Line : 1407
>> Explanation: An inner component is located in the wrong face.
>> Refer to the bug-reporting instructions at
>> http://www.cgal.org/bug_report.html
>>
>> Is this a bug, or am I not doing the right checks against the input
>> polygons?
>>
>> Chris
>>
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>>
>