CGAL users discussion list

[Efi Fogel <>]

Yes, compute_intersection_points() does not record the original curves.
It's on our todo list to add the option to record the original curves.
It's also in our todo list to expose the plane-sweep visitor.
You are welcome to contribute and try to implement anyone of the above. Your initial approach could work.

On Fri, Nov 16, 2012 at 10:03 PM, Ophir Setter <> wrote:

Basically you should use compute_intersection_points, but you want the original curves.
I don't know how to directly get this. It could be that you are right.

On Fri, Nov 16, 2012 at 5:19 PM, Winnie <> wrote:

Hello list!

I am trying to construct a map of all intersections within a set of
segments. The naive approach would take O(m²) time - but I'm aiming for
the O(m log m) of the Bentley-Ottmann algorithm.

It seems like the algorithm is implemented in the Sweep_line_2 module of
CGAL [1]. Unfortunately, there is not a lot of documentation about the
Sweep_line_visitor-Concept, which I tried to implement to get the
intersecting segments. Also it seems like I can not access the original
segments from the Sweep_line_visitor callbacks - only the generated
subcurves.

Is there somehow a possibility to get all intersecting segments for each
segment using CGAL? Possibly the easiest solution would be, to pass a
reference of the original segment to the Sweep_line_subcurve and then
access this within the visitor callback - which would require a
modification of the CGAL code as far as I understand it.

Best regards,
Winnie Hellmann

[1]
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Sweep_line_2/Chapter_main.html

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