Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!usc!rpi!uupsi!pixar!markv From: markv@pixar.com (Mark VandeWettering) Newsgroups: comp.graphics Subject: Re: polygon clipping Message-ID: <1991May7.181010.22047@pixar.com> Date: 7 May 91 18:10:10 GMT References: <2247@amsaa-cleo.brl.mil> <348@usna.NAVY.MIL> Sender: news@pixar.com (Usenet Newsmaster) Organization: Pixar -- Point Richmond, California Lines: 13 Nntp-Posting-Host: woody >>> 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. Well, we generally do mean interior clips when we speak about clipping to a rectangular region. And anyway, the exterior of a rectangle is not a convex set, so the original statement is correct as stands. mark