CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

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