CGAL users discussion list

[Dylan Lawrence <>]

I am using the Exact_circular_kernel_2

On Thu, Jul 9, 2015 at 1:00 AM, Sebastien Loriot (GeometryFactory) <> wrote:

What kernel are you using?

On 07/09/2015 01:06 AM, Dylan Lawrence wrote:

After a lot of wrestling I was able to get my code working, but I think
I'm missing something, below is my code and then the output

    Line_2 l(Point_2(2, 4), Point_2(6, 8));
    Circle_2 c(Point_2(3, 7),3);

    std::vector<IntersectOut> output;

    typedef CGAL::Dispatch_output_iterator <
    CGAL::cpp11::tuple<IntersectOut>,
    CGAL::cpp0x::tuple<std::back_insert_iterator<std::vector<IntersectOut>>>>
    Dispatcher;

    Dispatcher disp =
    CGAL::dispatch_output<IntersectOut>(std::back_inserter(output));
    CGAL::intersection(l, c, disp);

    if (output.size() > 0)
    {
    std::cout << CGAL::to_double(output[0].first.x()) << ", " <<
    CGAL::to_double(output[0].first.y()) << std::endl;
    std::cout << output[0].second << std::endl;
    if (output.size() > 1)
    {
    std::cout << CGAL::to_double(output[1].first.x()) << ", " <<
    CGAL::to_double(output[1].first.y()) << std::endl;
    }
    }


*Output*

    3.29289, 5.29289

    1

      4.70711, 6.70711


However on Wolfram using that circle and line it says the intersections
should occur at

    ((4-sqrt(7/2), 6-sqrt(7/2)) | (4+sqrt(7/2),
    6+sqrt(7/2)))~~((2.12917, 4.12917) | (5.87083, 7.87083))


This seems to be giving a different answer. I checked a few other cases
and some align with Wolfram but others are off like this and they seem
to be off by more than a floating point error.

On Tue, Jul 7, 2015 at 2:04 AM, Sebastien Loriot (GeometryFactory)
< <mailto:>> wrote:

    The type is boost::optional< boost::variant<T..> > where the types
    in the variant depends on what you call intersection with.
    In you case, it can only be
    std::pair<Circular_arc_point_2<CircularKernel>, unsigned>

    http://doc.cgal.org/latest/Kernel_23/group__intersection__circular__grp.html


    Have a look at the example on this page how to get the type out of
    the boost one:
    http://doc.cgal.org/latest/Kernel_23/group__intersection__linear__grp.html

    Sebastien.

    On 07/07/2015 08:56 AM, Dylan Lawrence wrote:

        After quite a bit of rewrites I was able to actually get the
        intersections running using CGAL::intersection() I know my vector
        contains the intersections however what exactly is in that
        vector. It
        seems to be an extension of a boost type but it's unclear what
        it is.
        Essentially I have my intersections, but I do not understand how to
        access them to get the point of incidence for an intersection.

        On Tue, Jun 23, 2015 at 12:55 PM, Laurent Rineau
        (CGAL/GeometryFactory)
        < <mailto:>
        <mailto:

        <mailto:>>> wrote:

             Le Tuesday 23 June 2015 16:22:27 Monique Teillaud a écrit :
             > a Line_arc_2 can be constructed from a Segment_2

         >http://doc.cgal.org/latest/Circular_kernel_2/classCGAL_1_1Line__arc__2.html
             >
             > then you can intersect it with a circle or a circular arc

         >http://doc.cgal.org/latest/Circular_kernel_2/classCircularKernel_1_1DoInters
             > ect__2.html
             > Le 23/06/15 04:22, dlawre14 a écrit :
             > > I've done some searching of the docs but cannot find
        any entry of a
             > > Circle_2 and Segment_2 intersecting. Can such a thing
        be done or do I
             > > need to convert the Segment_2 to another type?

             See also :

                - the Intersect_2 functor:

        http://doc.cgal.org/latest/Circular_kernel_2/classCircularKernel_1_1Intersect__2.html

                - the corresponding 'do_intersect' and 'intersection' global
             functions
             overloads:

        http://doc.cgal.org/latest/Kernel_23/group__do__intersect__circular__grp.html
        http://doc.cgal.org/latest/Kernel_23/group__intersection__circular__grp.html

             --
             Laurent Rineau, PhD
             R&D Engineer at GeometryFactory http://www.geometryfactory.com/
             Release Manager of the CGAL Project http://www.cgal.org/


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        --
        Dylan Lawrence
        Masters Student
        Bioinformatics and Computational Biology



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Dylan Lawrence
Masters Student
Bioinformatics and Computational Biology

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Dylan Lawrence

Masters Student

Bioinformatics and Computational Biology