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The Datafile PD-CD 3
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utilities
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utilss
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stereogram
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Text File
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1995-01-24
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7KB
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137 lines
-- Random-dot-auto-stereo-gram-type-things --------------------------------
------------------------------------------------------ Colin McEwan 1995 --
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(that's just an introductory graphic — view as black on white, from a
distance, then you'll get it)
Yes folks, it's time to go all cross-eyed, stare at your reflection for
hours on end, or stick your nose right up to the monitor in a vain attempt
to see what on earth is supposed to be going on! Yes, it's a whole load
of... Random-Dot-Autostereograms!!!
What?
Never seen them?
What planet 'you been on?
Okay, I'll explain.
If you've seen the "Magic Eye" books, or posters, or things, in shops like
Athena, or on the side of Pepsi bottles, and haven't been able to work out
what they are supposed to be, then that's what they are — Random-Dot-
Autostereograms. What you do is you look /through/ them, and because of the
repeating pattern of the dots, you should see a solid image. Simple as
that...
However, actually viewing them is a knack which not everyone has, or rather,
is prepared to acquire. However, with a bit of practice, you should find
you're able to just let your eyes drift out of focus and stare through the
page/screen, and see the solid image beyond. Some methods which are helpful
are:
• Pushing your face right up to the page/monitor, forcing your eyes to look
past the physical object. Once this is done, slowly draw your face away
until the image is in focus, and once you've locked onto it, bingo!
• Look at your reflection in the monitor, and then let your eyes drift back
to the actual screen (slowly, mind you, slowly...), and somewhere
inbetween, you should find the image.
• If you have an inkjet or a laser printer, try printing out a stereogram
on acetate. You should be able to look through the acetate and see what's
beyond, and also the image! I've yet to try this myself (the only acetate
I have isn't for inkjets)
There should be several images here:
• Acorn : An "Acorn" logo;
• Computer : A (3/4)00 series machine, without a mous, but still
recognizable;
• Forest : Lots of trees!
• hand : A handprint! (stuck my own hand on the monitor, and !Drew
round it;
• Helix : A horizontal helix. Maybe I'll change it to a vertical one,
as it should be easier to see... hang on... There, 'tis
done;
• SineScape : Umm, a sine-wave landscape (and skyscape, actually...);
• Sphere : A sphere!;
• Spiral : Uh... An odd, spiralling thing;
«• Sunny : A smiley sunny face thing;»
Each has a little thumbnail that shows you what the image is supposed to be
like (you may find this helps to see them if you're not too well practised).
I've adapted my original algorithm (which I worked out a LONG time ago when
the things first came into fashion) so that it can take a sprite file as
input, black at the back, white at the front, so I can build up the 3D
images by layers, rather than always using formulae for the shapes (also,
this makes it far faster).
One thing I'm going to try is this, if ever I get the chance: find an
object, and a flatbed scanner. Put the object on the scanner, scan, apply
heavy alpha-correction to the image, run through the stereogrammiser (!),
and hey presto! A 3D representation of the original object! (With any
luck...)
Also, I've another variation on the algorithm which uses a repeating
pattern, rather than random dots to generate the image. This has 2
disadvantages: i) it's difficult to tell exactly where the change between
different levels takes place if the pattern has any sort of solid colour, so
this appears to be a smooth gradation; ii) it uses loads of OS_SpriteOps, so
it's sslllloooooooowwwwwwwwwwwwwwww, if you get the picture. Maybe I'll do
one just now...? Hold hard awhile.
There, a nice sunny sunny-type 3D image! :-) Whew, that took a while to
render...
Maybe I'll release the software as Freeware sometime, but as it stands, they
need a lot of tidying up first...
These images are © Colin McEwan 1995. They may be freely copied about,
printed, published, etc. so long as this file is included with them. Cheers.
Colin McEwan
11 Helen Way
Alexandria
Strathclyde
G83 9PJ