Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!rpi!uupsi!eye!erich
From: erich@eye.com (	Eric Haines)
Newsgroups: comp.graphics
Subject: Re: Point in Polygon; a few more comments
Message-ID: <1990Sep07.161141.1788@eye.com>
Date: 7 Sep 90 16:11:41 GMT
References: <1990Sep06.124709.996@eye.com> <33619@cup.portal.com>
Reply-To: erich@eye.com (	Eric Haines)
Organization: 3D/Eye Inc., Ithaca, NY
Lines: 23

In article <33619@cup.portal.com> ekalenda@cup.portal.com (Edward John Kalenda) writes:
>Sorry to be a poop Eric, but my boss at Calma, Steve Hoffman, told me
>about the "points on the ray are above the ray" thing in 1981. He claimed
>someone told HIM several years before.
>
>I think it's one of those things that just need to be attributed to the
>anonamous coder.

	Oh, well, at least I can claim to be the first to publish!  Sadly
enough, the word still hasn't fully percolated out.  The latest Foley & Van
Dam (& Feiner & Hughes) says on page 34:  "Next, choose a ray that starts at
the test point and extends infinitely in any direction, and that does not pass
through any vertices".  Page 339 makes reference to "intersections at vertices"
being a "special case".  Passing through a vertex is still considered to be a
problem (even though it isn't).

	It's this kind of thing that makes me happy to see books like
"Graphics Gems" come out.  Letting the world know about the little tricks of
the trade saves us all a lot of time and replication of effort (I sure wish I
had known about the "above the ray" trick in 1986 - it would have saved me
hours of struggle).

Eric Haines