Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wasatch!sunset.utah.edu!u-jmolse
From: u-jmolse%sunset.utah.edu@wasatch.UUCP (John M. Olsen)
Newsgroups: comp.graphics
Subject: Re: 3-D perceptual abilities
Summary: Only one message per pattern (usually)
Message-ID: <1274@wasatch.UUCP>
Date: 9 Mar 89 20:44:34 GMT
References: <207400002@s.cs.uiuc.edu> <1247@wasatch.UUCP> <1276@dukeac.UUCP>
Sender: news@wasatch.UUCP
Reply-To: u-jmolse%sunset.utah.edu.UUCP@wasatch.UUCP (John M. Olsen)
Organization: University of Utah, Computer Science Dept.
Lines: 34

In article <1276@dukeac.UUCP> klg@dukeac.UUCP (Kim Greer) writes:
>u-jmolse%sunset.utah.edu.UUCP@wasatch.UUCP (John M. Olsen) writes:
>+Okay, all you cross-eyed folks.  Read this:
>+[random looking stuff]
>  Has anyone ever used this as a crypto mechanism ?  With several different
>offsets in the same message, maybe you could get several messages in the
>same "paragraph".  
>Kim L. Greer                       
>Duke University Medical Center		try: klg@orion.mc.duke.edu
>Div. Nuclear Medicine  POB 3949            dukeac!klg@ecsgate
>Durham, NC 27710  919-681-2711x223 ...!mcnc!ecsgate!dukeac!klg	fax: 919-681-5636

I have thought of posting things on the wall where everyone can look, but 
none can see. :^)  With a decent random number generator, you can generate
stastically random output when making these stereo illusions, making the
output look like pure noise.

Sorry, but you can generally only put one message in a random pattern.  If
you pull some sneaky tricks, you can get two, but you can't see both from
the same angle.  If you overlap by incorrect multiples of the repeat
frequency, the pattern sort of disintigrates and looks about like two lines
of text typed on top of each other.  If the original starts with one offset
level, then "missing" by one repeat width will make it appear to have an
extra altitude level of "noise" scattered throughout the image.

Of course this means that you can purposely generate multiple altitude
levels in the illusion.  I have several such bit mapped printouts sitting
around the house-- some hand drawn (computer paint program), and some 
computer generated.  Hand drawing these things is not a trivial task.

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