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From: dfr@usna.NAVY.MIL (Prof. David F. Rogers)
Newsgroups: comp.graphics
Subject: Re: polygon clipping
Message-ID: <348@usna.NAVY.MIL>
Date: 25 Apr 91 01:43:23 GMT
Article-I.D.: usna.348
References: <2247@amsaa-cleo.brl.mil> <LAMBERT.91Apr23232842@silver.cs.umanitoba.ca>
Organization: U. S. Naval Academy, Annapolis, MD
Lines: 12

In article <LAMBERT.91Apr23232842@silver.cs.umanitoba.ca> lambert@silver.cs.umanitoba.ca (Tim Lambert) writes:
>>>>>> On 23 Apr 91 10:24:09 GMT, neiderer@amsaa-seer.brl.mil (Andrew Neiderer ) said:
>
>> Will clipping a triangle to a rectangular region always result
>> in a convex polygon (or no polygon at all) ? 
>
>Yes, because the intersection of two convex sets is convex.

No, it depends on whether you do an INTERIOR or an EXTERIOR clip.
If you do and EXTERIOR clip you can get a concave polygon.

Dave Rogers