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[Ophir Setter <>]

The basic arrangement class does not care about the "direction" of the curves. Even though that the two curves have different "directions" they consist the same group of points in the plane, and thus, only one edge is required to represent them in the DCEL. The basic concept for the arrangement class does not require a direction for the curves.

You can, however, use the Arrangement_with_history_2 class to get, for each edge, a mapping to all its inducing curves:
http://www.cgal.org/Manual/3.4/doc_html/cgal_manual/Arrangement_on_surface_2_ref/Class_Arrangement_with_history_2.html

On Wed, Apr 1, 2009 at 8:38 PM, Ben Supnik <> wrote:

Hi Y'all,

I am trying to figure out how opposite-direction, identical-supporting-line curves are merged with the arrangement_2 package.

- If I insert a curve and at least part of the curve is "on top of" (but opposite direction) an existing curve, what happens?  (I _think_ in this case the newly inserted curve is _not_ inserted for this section.

- If I merge two maps that contain opposite direction, overlapping curves, which "direction" is chosen to make the new sub-curve representing the overlapping region?

(This is the case that I have no idea about...I looked through sweep_line_2 and the overlay visitor, and it appears that the choice of which direction to take is deterministic, but the sweep code makes my head hurt.)

cheers
ben
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