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Subject: Re: [geometry] calculating intersections on a self-intersecting line
From: Barend Gehrels (barend_at_[hidden])
Date: 2013-11-11 17:53:50

Hi Joan,

joan wrote On 6-11-2013 14:22:
> Hi,
> I'd also need to know in the case of a self-intersection on a polygon on
> which points the self intersection occurs. And even better on which segment
> of my polygon !

This can be done by calling the (not yet documented) function self_turns

It returns "turn-info" points, each point has an intersection point,
including the segment-identifier (exactly giving the causing segments of
your polygon).

Best reference is in the unit-test self_intersection_points.cpp where it
is called.

Note that there are some issues left in self-intersection points, for
example a self-tangent point is sometimes reported too (but it should be
excluded). Will be fixed soon.

Regards, Barend

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