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Re: [cgal-discuss] Sweep algorithm return intersecting segments


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  • From: Benjamin Streitz <>
  • To: Efi Fogel <>,
  • Subject: Re: [cgal-discuss] Sweep algorithm return intersecting segments
  • Date: Thu, 12 Jul 2018 16:14:41 +0200 (CEST)
  • Authentication-results: mail3-smtp-sop.national.inria.fr; spf=None ; spf=None ; spf=Pass
  • Importance: Medium
  • Ironport-phdr: 9a23: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

Thx. I think
https://doc.cgal.org/latest/Arrangement_on_surface_2/Arrangement_on_surface_2_2curve_history_8cpp-example.html
is an even better example which I found originating from your example,
assuming one doesn't want to define an observer.

One more question about performance. Does this approach have the same
performance of O((n+k)log(n)) as the sweep algorithm itself or is that only
true for a single insert() operation?

> Efi Fogel
> <>
> hat am 12. Juli 2018 um 12:29 geschrieben:
>
>
> Consider constructing a 2d-arrangement induced by the curves (using the
> aggregate insert() free function, which is based on the surface-sweep
> framework).
> In particular, construct an object the type of which is an instance of
> Arrangement_with_history_2, or extend the arrangement to your needs and use
> an observer to update the extended data (see, e.g., the face_extension.cpp
> example of the Arrangement_on_surface_2 package).
> All the information you mention can be extracted from the arrangement
> object.
>
> ____ _ ____ _
> /_____/_) o /__________ __ //
> (____ ( ( ( (_/ (_/-(-'_(/
> _/
>
>
>
> On 12 July 2018 at 13:14, brainslush
> <>
> wrote:
>
> > I have a list of segments and want to determine where and with what
> > other segments they are intersecting unsing the sweep algorithm.
> > The part for obtaining the intersection positions is straight forward
> > from the tutorial / example.
> > https://doc.cgal.org/latest/Surface_sweep_2/index.html
> >
> > What steps would I have to take to obtain the the segments/curves
> > involed in the intersection?
> >
> > Kind Regards,
> > Benjamin
> >
> >
> >
> >
> > --
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> >
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