Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!umd5!rutgers!bellcore!faline!thumper!mike
From: mike@thumperbellcore.com (Michael Caplinger)
Newsgroups: comp.sys.mac
Subject: Re: 3-D Graphics Question
Message-ID: <883@thumperbellcore.com>
Date: 10 Dec 87 21:26:46 GMT
Organization: Bell Communications Research
Lines: 18
Keywords: geometric transform, photoclinometry

If all you want to do is rotate the image such that you get a straight-down
view of it, a simple geometric transformation with some kind of
bilinear interpolation will do what you want -- a little guesswork about
slant angles is all that's needed.  Try looking in an elementary image
processing book.  I don't know of any commercial software that'll
do this, but it's easily within the processing power of a Mac, if
you don't mind waiting a few tens of minutes per transformation.

Getting elevation data from a single image can also be done, given
a knowledge of lighting angle and surface reflectivity characteristics;
it's like doing image synthesis backwards, and the process is usually
called photoclinometry.  Such techniques have been used on data from
the Voyager mission since stereo pairs typically weren't available.

I'm a little bemused by peoples' reactions to this problem; it just isn't
as hard as y'all thought...

	Mike Caplinger, mike@bellcore.com