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From: chapman@fornax.uucp (John Chapman)
Newsgroups: comp.graphics
Subject: Re: Liang-Barsky Polygon Clipping Questions
Message-ID: <238@fornax.uucp>
Date: Mon, 9-Mar-87 23:38:21 EST
Article-I.D.: fornax.238
Posted: Mon Mar  9 23:38:21 1987
Date-Received: Wed, 11-Mar-87 05:03:21 EST
References: <252@naucse.UUCP> <14597@sun.uucp>
Organization: School of Computing Science, SFU, Burnaby, B.C. Canada
Lines: 23

> In article <252@naucse.UUCP> sbw@naucse.UUCP (Steve Wampler) writes:
> >The November 1983 Issue of CACM has a nice polygon clipping
> >algorithm by Liang-Barsky, including Pascal code for the
> >algorithm.
> >
> >However, when I tried out the algorithm, I found a number of
> >cases where it did not work correctly.
> 	 [...]
> >   (1)  Does the algorithm as given in that CACM issue work?
> 	 [...]
> >   (2)  If not, then was there a published fix to it?
> >   (3)	If so, then can someone point me to it or provide it
> >	to me?
> 
> Make sure to check the Corrigendum in the April 1984 CACM.
> There was also one in Feb '84, but the April one was cumulative

In 1984 I implemented the corrected algorithm and it seemed to work
in all cases.  The only thing which gave me pause was that while I
implemented the alg. on the same hardware and language as in the
article (and the same data) my timing results differed from the
published ones by an order of magnitude.