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Re: [cgal-discuss] halfedges


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  • From: Olivier Devillers <>
  • To:
  • Subject: Re: [cgal-discuss] halfedges
  • Date: Mon, 27 Oct 2008 09:44:58 +0100

Hanjoerg Seybold a écrit :
Hi!
Nobody has an idea how to obtain the direction of infinite halfedges?
thanks hj
Hanjoerg Seybold writes:
Hello!
I am making calculations with voronoi diagrams. For my application i have to intersect the unbounded edges/halfedges with a boundary given by a polygon or a segment or line. After studying the manual and i am a bit confused about the halfedge structure. 1. it is said that "Halfedges are oriented edges", but i cannot find a
method how to access the orientation.
from source to target !

2. It is possibe to check if a halfedge IS a segment or ray. h.is_ray(),
but if the halfedge IS a ray, how can i access its features (direction,
etc.)?
I agree that such a function should be there.

Anyway you can get dual()->segment() to get the dual Delaunay edge
and rotate it by 90 d. to get the direction

3. My Problem is that i iterate through the halfedges and i want to know if
a infinite halfedge intersects a polygon. For this i wanted to construct
a line ray etc out of the halfedge, but i dont know how to obtain the
direction in the case that the halfedge has only source OR target. Any help would be welcome hansjoerg
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