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["Amir Vaxman" <>]

The case you discuss is not a “split event” , it is what Eppstein & Erickson called a “vertex event” in his article:

 

@article{EppsteinErickson,

 author = {D. Eppstein and J. Erickson},

 title = {Raising roofs, crashing cycles, and playing pool: applications of a data structure for finding pairwise interactions},

 journal = {Proc. 14th Ann.\ Symp.\ on Computational Geometry, \upshape{58--67}},

 year = {1998},

 address = {Minneapolis, MN},

 }

 

It occurs on the degeneracy where two reflex vertices meet, and should be handled accordingly. What happens after this event, is that the newly-created vertex is a vertex between two collinear edges. It is not one edge.

 

From: xiangzhi wei [mailto:]
Sent: Thursday, November 22, 2007 4:02 PM
To:
Subject: Re: [cgal-discuss] Straight Skeleton original code

 

Hi Fernando Cacciola !

Thanks very much for your help!

Two degeneration cases are listed in the attachment. if there are at least two becoming edges collinear during the shrinking process. As a result, the shape of straight skeleton seems incorrect !!

If you have some good idea, please let us know.

Best regards,

Xiangzhi

2007/11/22, Fernando Cacciola <>:

Hello Xiangzhi

> Hi all !
>
> I wanna if there is any original code for straight skeleton on CGAL. There
> is something wrong with the software titled "Straight_Skeleton_2" when it
> comes to those cases when at least two disjoined edges came into collinear
> during the shrinking process of the original polygon.
>
There is a bug fix for the Straight Skeleton package which unfortunately
couldn't be incorporated into CGAL 3.3.1.
I'm attaching the patch in this message.
Can you please try again after installing the patch and report on the list if
you still find a problem?

Just unzip the attached file right there into the top level folder of a CGAL
installation.

> And I wanna do some experiments to test it further, but I cannot find its
> original C++ code.
>
What you mean by original C++ code?

TIA

Fernando Cacciola
GeometryFactory

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