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From: thale@novell.com (Todd D. Hale)
Newsgroups: alt.3d
Subject: SIRDS/Stereogram/Stare-E-O FAQ
Date: Mon, 4 Apr 1994 23:16:54 GMT
Organization: Novell, Inc., Provo, UT, USA
Lines: 897
Message-ID: <thale.20.2DA09FE5@novell.com>
NNTP-Posting-Host: thale.npd.provo.novell.com
The following is a smattering of info I've collected about SIRDS. It is not
totally organized, nor complete, but it answers a lot of FAQs out there.
Please submit any updates/changes to me at thale@novell.com.
The following sections are covered herein:
Stereogram Terminology
Stereogram FTP Sites
Commercial SIRDS Software
Stereogram Publications
Sample TEXT Stereograms
How Single Images Stereograms work
Stereogram Algorithm
C Code to Generate SIRTS
Hope for the Hopeless
Commercial Stereogram Producers
-----------------------------------------------------------------------
----- STEREOGRAM TERMINOLOGY ------------------------------------------
-----------------------------------------------------------------------
The definitions below are listed hierarchically (a SIRDS is a SIS is a
Stereogram):
Stereogram
Any stereo picture using stereo pairs or multiple repeating
patterns
Stereo Pair
Two pictures from slightly different viewpoints, as used in
the old handheld viewers and viewmasters
SIS (Single Image Stereogram), Autostereogram
Includes SIRDS, SIRTS, Single Image Rendered Data Stereogram;
extends stereo pair concept to "stereo megtuples"
SIRDS (Single Image Random Dot Stereogram), RDS, AutoRDS, Random
Dot Anaglyphs
Repeating image is made up of random dots
RLS (Random Line Stereogram)
Original repeating image is made up of vertical lines of
varying widths; very instructional, see Slinker and Burton
paper
SIRTS (Single Image Random Text Stereograms), ASCII stereograms
Repeating image is made up of random text characters
SITS?
Non random text stereograms; see Sample Text Stereograms,
done manually for sigs and such
a SIRD (Single Image Random Dot)
not much to view in a dot; used by newbies :-)
Wall-eyed viewing
Viewing stereograms by focusing past the actual image
Cross-eyed viewing
Viewing stereograms by focusing in front of the image
Focusing to infinity
Forcing your eyes' lines of sight into parallel, NOT
necessary for wall-eyeing SIRDS! (only occurs when the length
of the repeating pattern = distance between centers of eyes)
-----------------------------------------------------------------------
----- STEREOGRAM FTP SITES --------------------------------------------
-----------------------------------------------------------------------
Submissions from michael@eccles.anu.edu.au, E.Thompson@newcastle.ac.uk,
kbaum@novell.com, ...:
THE FTP SITE for Stereograms is KATZ:
katz.anu.edu.au ()
/pub/stereograms
00Index.txt - This listing
00Readme.txt - An introduction to this site
ls-lR - Full list of files under this directory
SIRDS.FAQ - This file, created by Todd Thale (thale@novell.com)
ascii/ - ASCII stereograms
blue_red/ - Stereograms requiring Blue/Red glasses
een/ - Single Image Stereograms created by EEN
in both TIFF and BMP formats
images/ - Single Image Stereograms (some GIF and PS)
ls-lR - Directory listing of all stereogram files
papers/ - Papers on single image stereograms
programs/ - Programs for creating and viewing stereograms (IBM,
X and Unix)
mac/ - Programs and Images for Apple Macintosh computers
acorn/ - Programs and Images for Acorn Archimedes range of
computers
WWW access for MOSAIC users:
http://h2.ph.man.ac.uk/gareth/sirds.html
From Gareth Richards (gareth@v2.ph.man.ac.uk, richards@cernvm.cern.ch,
gareth@h2.ph.man.ac.uk)
OTHERS (Most of this is available at katz, above):
ftp.uwp.edu (131.210.1.4)
/pub/msdos/picture.viewers/rdsdraw.zip
EXCELLENT SIRDS painting/generating program. CHECK IT OUT!
oak.oakland.edu
/pub/msdos/graphics/mindim20.zip
/pub/msdos/graphics/sirdvu11.zip
/pub/msdos/graphics/perspect.zip
wuarchive.wustl.edu (128.252.135.4)
/pub/xpgs/xpgs
/pub/MSDOS_UPLOADS/graphics/dynamic.exe
/graphics/graphics/mirrors/sugrfx.acs.syr.edu/3d/randot/3drandot.zoo
sunsite.unc.edu
/pub/academic/computer-science/virtual-reality/3d/*
ftp.cs.waikato.ac.nz
/pub/papers/???.tar.Z
gwaihir.dd.chalmers.se
pub/een/SIS/*.tif
pub/een/Dirk-SIS/*.tif <-- GET THESE (not on katz, yet)
-----------------------------------------------------------------------
----- COMMERCIAL SIRDS SOFTWARE ---------------------------------------
-----------------------------------------------------------------------
STW_DEMO.EXE: the full package will allow RDS creation
Approx 40$
N.E.Thing Enterprises
P.O. Box 1827
Cambridge, MA 02139
A company called I/O Software, Inc. (909/483-5700 800/800-7970)
has a program called STEREOLUSIONS. It works on both WINDOWS and
Windows NT and allows people to create, render and even print SIRDS on
any Windows compatible machine. (From William Saito, 3/07/94)
KAI's POWER TOOLS for the MAC has a Photoshop add-on for SIS creation.
Stareo-3D ??
SEND MORE INFO!
-----------------------------------------------------------------------
----- STEREOGRAM PUBLICATIONS -----------------------------------------
-----------------------------------------------------------------------
Search library databases with these keywords: Stereogram, Autostereogram,
SIRDS (Single Image Random Dot Stereogram), RDS.
Considered by most as the original work on Random Dot Stereograms:
'Principles of Cyclopean Perception' by Bela Julesz, from MIT press, circa
1972.
>Charles Eicher (CEicher@Halcyon.com)
An excellent source of information (sample RDS and source code)
is contained in Andrew A.Kinsman - Random Dot Stereograms
ISBN 0-9630142-1-8 $13.95 U.S. Published by Kinsman Physics,
P.O. Box 22682, Rochester, N.Y. 14692-2682
>E.Thompson@ncl.ac.uk
Journal of Imaging Science and Technology, May/June 1992, Vol 36, #3.
Slinker & Burton. Their use of random line stereograms really helps
to understand how stereograms work, as well as some of their limitations.
New Scientist (9 October 1993) has a 4 page article on SIRDS. There is a
pretty cool example too.
>Simon Dear (sd@mrc-lmb.cam.ac.uk)
David G. Stork and Chris Rocca. "Software for generating auto-random-dot
stereograms", Behavior Research Methods, Instruments, and Computers,
Vol. 21, No. 5, 1989, pp. 525-534.
>Steve Tate (srt@cs.unt.edu)
"Stereo Computer Graphics and Other True 3D Technologies"
David F. McAllister, Ed.
Princeton University Press, 1993
ISBN 0-691-08741-5 US$75.00
It has several nice color plates, with stereo "triads". The triads consist
of a left, a right, then another left image. Use the left pair for viewing
walleyed, or the right pair for viewing crosseyed.
>Mike Weiblen (mew@digex.net)
"Stereogram" (c) 1994, Cadence Books, San Francisco, CA
"a newly edited version of CG STEREOGRAM and CG STEREOGRAM 2,
published by Shogakukan Inc. In Tokyo, Japan"
ISBN 0-929279-85-9
Cadence Books, A division of Viz Communications, Inc.
P.O. Box 77010
I liked it. Much better in my opinion than the other Stereogram
book I've seen ("Magic Eye"). This one includes much textual
information, including the origins of stereograms, how to see them,
precursors such as stereo pairs, and an article by Christopher W.
Tyler, who invented the SIRDS.
Best of all were the stereograms themselves. There are roughly
50 SIRDS, most of them full page (the book is softcover and about 8"
square). The ones I've managed to see so far have been quite good,
and also included are some of the very first ones. In the history
department there are stereo pairs, stereo photographs, and even some
stereo-pair paintings by Salvador Dali.
All of the stereograms indicate whether they require wall-eyed or
cross-eyed viewing (or either). Most are true 3d designs, not the
"cutout" variety.
The book is 93 pages and most of the plates are full-color.
Well worth the money in my opinion.
>Michael Moncur (mgm@xmission.com)
_Magic Eye: A New Way of Looking at the World_
copyright (c) 1993 by N.E. Thing Enterprises.
Andrews and McMeel, A Universal Press Syndicate Company, Kansas City
ISBN: 0-8362-7006-1
First Printing, September 1993 ... Fifth Printing, January 1994
Introduction contains a history of the technique and phenomena.
Viewing Techniques are explained. 25 pages of full-color STARE-E-O images.
(Plus images inside the front and back covers.) "Answers" included.
32 pages, hardcover, 8.75x11.5 inches, horizontal format, with slipcover.
US$12.95 ($16.95/Canada)
I just bought this for US$7.77 at Media Play in Utah. It's currently on
their best seller list. Well worth any price under $30!
>Todd Hale, 3/25/94
Magic Eye II: Three Dimension Trip Vision
Copyright 1992 by N.E. Thing Enterprises/Tenyo Co., Ltd.
Korean Translation Copyright 1993 by Chungrim Publishing Co.
All the text is in Korean, so I can't read it. But it has some pretty
cool pictures. They are all SIRxS where x is various patterns/pictures.
I paid US$20 for it. Interestingly, this title doesn't seem to be mentioned
in my N.E. Thing catalog.
>Mark Hudson (M_Hudson@delphi.com)
SEND MORE REFERENCES!
-----------------------------------------------------------------------
----- SAMPLE TEXT Stereograms (Not random) ----------------------------
-----------------------------------------------------------------------
From: dthomas@bbx.basis.com (Dave Thomas)
O O
n n n n n n n n n n n n n n n n
f f f f f f f f f f f f f
e e e e e e e e e e e e e e e e
a a a a a a a a a a a a a
a a a a a a a a a a a a a a a a
r r r r r r r r r r r r r
r r r r r r r r r r r r r r r r
g g g g g g g g g g g g g g g g g g g g g g g g g
r r r r r r r r r r r r r r r r r r r
e e e e e e e e e e e e e e e
a a a a a a a a a a a a a
t t t t t t t t t t t
<<<<>>>><<<<>>>><<<<>>>><<<<>>>><<<<>>>><<<<>>>><<<<>>>><<<<>>>><<<<>>>>
d d d d d d d d d d d
e e e e e e e e e e e e e
p p p p p p p p p p p p p p p
t t t t t t t t t t t t t t t t t t t
h h h h h h h h h h h h h h h h h h h h h h h h h
From: jittlov@gumby.cs.caltech.edu (Mike Jittlov)
. . . . . . . .
@ . @ . @ . @ .
> /^\ /^\ /^\ /^\ /^\
> ####################################################################
> ####################################################################
> / #### / ####\ / #### \ / #### \ /#### \
>/ ## \__/ ## \__/ ## \__/ ## \__/ ## \
> ____ ## ____ ## ____ ## ____ ## ____ ## ____
> / \## / \ ## / \ ## / \ ## / \ ##/ \
> | 2D |# | 2D |## | 2D | ## | 2D | ##| 2D | #| 2D |
> | or |# | or |## | or | ## | or | ##| or | #| or |
> | 3D |# | 3D |## | 3D | ## | 3D | ##| 3D | #| 3D |
> | ?? |# | ?? |## | ?? | ## | ?? | ##| ?? | #| ?? |
> | | | | | | | | | | | |
> -------- -------- -------- -------- -------- --------
> \\\\\\\\ \\\\\\\\ \\\\\\\\ \\\\\\\\ \\\\\\\\ \\\\\\\\
> \\\\\\\\ \\\\\\\\ \\\n\r\\ \\f\o\d\ \\\\\\\\ \\\\\\\\
> \\\\\\ \\\\\\ \\\\\\ \\\\\\ \\\\\\ \\\\\\
> DR J
_____________________________________________________________________________
[] [] [] | [] [] [] [] | [] [] [] [] | [] [] [] [] | [] [] [] [] | [] [] []
=============================================================================
* : * : * : * : * : *
.' `: .' `. : .' `. : .' `. : .' `. :' `.
Mike Jittlov Mike.Jittlov Mike Jittlov.Mike Jittlov Mike Jittlov Mike Jittlov
The Wizard` The Wizard. The Wizard . The Wizard .The Wizard 'The Wizard
* * of . * * of * * of * . * of * * of* * . o* *
|\^/|peed . |\^/|Speed |\^/| Speed |\^/| Speed|\^/| Spee|\^/| . Spe|\^/|
\V/ and . \V/ and .\V/ and \V/ and \V/. and \V/ . and\V/
/_\Time! . /_\ Time! ./_\ Time! /_\ Time! /_\. Time!/_\ . Time/_\
_/ \_ . _/ \_ _/ \_ _/.\_ _/ \_ _/ \_ . _/ \_
=============================================================================
WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
One more from ... well ... YOU figure it out!
_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~
! Adam Adam Adam Adam Adam Adam ! "Lawn !
!Spragg Spragg Spragg Spragg Spragg Spragg Spragg! service!" !
! Adam Adam Adam Adam Adam Adam ! -Stup !
!Spragg Spragg Spragg Spragg Spragg Spragg Spragg! !
! Adam Adam Adam Adam Adam Adam ! atspragg@ !
!Spragg Spragg Spragg Spragg Spragg Spragg Spragg! ucdavis.edu !
! Adam Adam Adam Adam Adam Adam ! GO AGS! !
_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~-_-~
-----------------------------------------------------------------------
----- How Single Image Stereograms Work -------------------------------
-----------------------------------------------------------------------
Let's start with a simple repeating pattern. First we'll examine viewing
stereograms wall-eyed (focusing beyond the picture).
Adam
Adam Adam <-- PERCEIVED IMAGE (3D)
\
\ \
\ \
Adam Adam Adam Adam <-- ACTUAL PICTURE (Flat, 2D)
\ \
\ \ <-- LINES OF SIGHT FROM EACH EYE
\ \
(*) (*) <-- EYES
As shown in the above graphic, the lines of sight go through different
(but identical) words. The eyes must be directed to just the right level
behind the picture to get the two "Adams" to line up. When they do line
up, a single "Adam" appears at the level shown behind the picture.
This is why it is easiest for some people to look at stereograms behind
glass. You simply look at your reflection, which appears to be behind
the glass at about the same level as the 3d stereogram image. More on
this later.
So, why is the second "Adam" in the above image "deeper" than the other
two? Since the next two "Adams" that line up are FARTHER apart than the
first two, your eyes must diverge a little more to get them to line up.
As the eyes diverge, their lines of sight meet a little further away.
This causes the next "Adam" to appear deeper in the image.
Adam
Adam | Adam <-- PERCEIVED IMAGE (3D)
/ \
/ \
/ \
Adam Adam Adam Adam <-- ACTUAL PICTURE (Flat, 2D)
/ \
/ \ <-- LINES OF SIGHT FROM EACH EYE
/ \
(*) (*) <-- EYES
The above graphic was crammed into 10 lines of text. If we moved the
eyes back (to a more realistic distance), the whole 3d image would
appear deeper, and not so spread out.
Cross-eyed viewing follows the same principles, but brings the focal point
up front of the picture and inverts the image. I'll use the same eyes and
picture, but move the eyes back for room to illustrate.
Adam Adam Adam Adam <-- ACTUAL PICTURE (Flat, 2D)
\ |
\|
Adam <-- PERCEIVED IMAGE (3D)
| \
| \
| \ <-- LINES OF SIGHT FROM EACH EYE
| \
(*) (*) <-- EYES
Now for the inverse part. Since the next two "Adams" are farther apart,
you must cross your eyes MORE (converge instead of diverge your eyes) to
get the "Adams" to overlap. This causes the next "Adam" in the image to
appear closer than the first one.
Adam Adam Adam Adam <-- ACTUAL PICTURE (Flat, 2D)
\ /
\ /
Adam\ / Adam <-- PERCEIVED IMAGE (3D)
Adam
/ \
/ \ <-- LINES OF SIGHT FROM EACH EYE
/ \
(*) (*) <-- EYES
Whew. Ascii graphics are a bit too tight to be very technical. By the
way, each letter (or pixel) in the 3D image comes from two letters in
the picture. Stereograms have blurry edges (right and left edges)
because the line of sight from the one eye passes through the picture,
but the line of sight from the other eye is off the picture. Examine
the wall-eyed example below.
Adam
Adam Adam <-- PERCEIVED IMAGE (3D)
\
\ \
\ \
\ Adam Adam Adam Adam <-- ACTUAL PICTURE (Flat, 2D)
\ \
\ \ <-- LINES OF SIGHT
\ \
(*) (*) <-- EYES
Here, the line of sight for the right eye goes through first "Adam"
in the picture, and the line of sight for the left eye is off the
picture. (Everything to the left of the first "Adam" in the IMAGE
is blurry.)
HOW TO GENERATE STEREOGRAMS
Random stereograms work the same way; they simple repeat random text or
pixels, instead of words like the "Adam" used above. Below, the pattern,
"ASDFGHJK", is repeated four times in each line. (I duplicated it for
easier viewing.)
ASDFGHJKASDFGHJKASDFGHJKASDFGHJK
ASDFGHJKASDFGHJKASDFGHJKASDFGHJK
ASDFGHJKASDFGHJKASDFGHJKASDFGHJK
As you might guess, the image consists of THREE repetitions of the
pattern, set back behind the picture (wall-eyed). To add some varying
depth to the image, we can simple add a space in the middle; or better,
we'll add a different letter, the letter Q. I've also dropped the K
off the end to keep it suitable for framing. :-)
ASDFGHJKASDFGHJKASDFGHJKASDFGHJK
ASDFGHJKASDFGHJKASQDFGHJKASDFGHJ
ASDFGHJKASDFGHJKASDFGHJKASDFGHJK
Adding the Q has the same effect as adding the space between "Adams"
in the previous example. Here it is again for comparison.
Adam Adam Adam Adam Adam Adam
Adam Adam Adam Adam Adam Ada
Adam Adam Adam Adam Adam Adam
These two stereograms demonstrate going down a level (deeper, for wall-
eyed viewers) by adding a new letter where you want to go down. The
image returns back to the original level because the added letter was
not repeated down the line; it was essentially deleted again. Hence,
deleting a letter causes the image to come forward one level. Lets
look at this by deleting a letter before adding any.
ASDFGHJKASDFGHJKASDFGHJKASDFGHJK
ASDFGHJKASDFGJKASDFGHJKASDFGHJKA
ASDFGHJKASDFGHJKASDFGHJKASDFGHJK
I deleted an H from the middle row, and added an A on the end to make
it flush again. This causes the image to come up a level where the H
was deleted, then go back down where the H returns to the pattern.
To fully control the ups and downs of stereogram generation, you simply
keep track of what's repeating and add and delete letters when needed.
For example, start with the pattern ASDFGHJK. If the input for the 3D
stereogram image is 00000000000011111222221111111110000, where the
numbers represent the levels of the 3D image, you simply delete a letter
from the pattern when you go up a level (0 to 1, or 1 to 2), and add a
letter to the pattern when you go down a level (2 to 1, or 1 to 0).
If you want to go up multiple levels, e.g., from level 1 to 3, delete
2 letters from your pattern. Adding two letters to the pattern likewise
causes a two-level drop in the image.
Start each line of the image by dumping the whole pattern. Recall that
in the examples above, four "Adams" in the picture creates three "Adams"
in the image. By dumping the pattern to start, we are simple providing
the first "Adam" to build the 3D image from. Now, we start building the
3D image.
ASDFGHJK
Since the first 12 levels are at level 0, we do no adding nor deleting;
just dump 12 more letters from the pattern in order.
ASDFGHJKASDFGHJKASDF
^image starts here
We now have our first transition, from level 0 to 1. Which letter do we
delete? Delete the next one in the pattern.
ASDFGHJK
^the next letter in the pattern
Since G is next, we delete it. Our new pattern is ASDFHJK, and H is the
next letter to be used in the image.
ASDFHJK
^the next letter to use in the image
Forget about the G. Consider it gone forever. The input now indicates
five letters at level 1. Since we made the transition to level one by
deleting the G, we simply copy the next 5 letters from the pattern into
the image. The next 5 letters in the pattern are HJKAS. (You've noticed
by now that we wrap around when we get to the end of the pattern.) I'll
lay the input next to our image to make it easier to see where we're at.
00000000000011111222221111111110000
ASDFGHJKASDFGHJKASDFHJKAS
{ }{ }{ }
initial level 0 level
pattern 1
To jump up to level 2 from level 1, we delete the next letter in the
pattern, the letter D. The new pattern is shown below.
ASFHJK
^the next letter to use
We have 5 letters at level 2, so we copy the next 5 letters from the
pattern, FHJKA, to the image.
00000000000011111222221111111110000
ASDFGHJKASDFGHJKASDFHJKASFHJKA
{ }{ }{ }{ }
initial level 0 lev level
pattern 1 2
We must now move down a level, from 2 to 1, by ADDING a letter to our
pattern. Where do we add it? Add it as the next letter to use. Let's
add an X (randomly chosen letters work better than previously used
letters). Since A was the last letter used, S is the next to be used.
ASFHJK
^add X here
AXSFHJK
^next letter to use
Since there are nine letters at level 1, we must copy nine letters
from the pattern to the image (XSFHJKAXS).
00000000000011111222221111111110000
ASDFGHJKASDFGHJKASDFHJKASFHJKAXSFHJKAXS
{ }{ }{ }{ }{ }
initial level 0 lev level level 1
pattern 1 2
Drop another level, from 1 to 0, by adding another letter to the pattern
at the current position.
AXSFHJK
^add random letter (M) here
AXSMFHJK
^next letter to use
Since there are four letters at level 0, we copy four letters from the
pattern to the image (MFHJ).
00000000000011111222221111111110000
ASDFGHJKASDFGHJKASDFHJKASFHJKAXSFHJKAXSMFHJ
{ }{ }{ }{ }{ }{ }
initial level 0 lev level level lev
pattern 1 2 1 0
WE'RE DONE. Kinda anti-climatic, huh? Let's duplicate the image line
to make it easier to view.
ASDFGHJKASDFGHJKASDFHJKASFHJKAXSFHJKAXSMFHJ
ASDFGHJKASDFGHJKASDFHJKASFHJKAXSFHJKAXSMFHJ
ASDFGHJKASDFGHJKASDFHJKASFHJKAXSFHJKAXSMFHJ
ASDFGHJKASDFGHJKASDFHJKASFHJKAXSFHJKAXSMFHJ
ASDFGHJKASDFGHJKASDFHJKASFHJKAXSFHJKAXSMFHJ
For each new line in the image, start with a new random pattern, and
follow the steps above. So, how are graphics stereograms made? The
same way, using colored pixel values for input. 3drandot uses RED as
the color deepest in the image, with GREEN in the middle, and BLUE as
the highest color.
The pseudocode below follows this algorithm. If you have any questions,
post them in the newsgroup. Let me know if you are interested in C code
that follows this algorithm. (The C code here in the FAQ follows a
different algorithm, the "lookback" algorithm.)
Enjoy!!
thale@novell.com
-----------------------------------------------------------------------
----- STEREOGRAM ALGORITHM --------------------------------------------
-----------------------------------------------------------------------
The following is an algorithm I developed for SIRDS generation. It is
functionally equivalent to the look back algorithms, without looking back.
It can be used for graphic stereograms, as well as the text stereograms.
It simply stores in PATTERN the values we would look back at. The input
file is depth data, or a z-buffer (see example input below). The levels
available in a picture are the maximum pattern size divided by two minus
one. Maximum pattern size should be equivalent to half the distance
between the eyes (for easy viewing), which is about 1 1/4 inches. So, for
typical text stereograms on an 80 char display, that's about 10 characters
for the maximum pattern size and 4 or 5 levels available. However, since
4 or 5 levels is unreasonable, we push the max pattern size to 16 (still
less that the 20 character distance between the eyes). This gives us about
7 or 8 levels.
If we do allow more than 7 levels when the max pattern size is 16, the
repeating pattern (of size max pattern - current level) grows so small that
four of them in a row (e.g., of size 7) would also create two double
patterns in a row (of size 14), causing floaties (aliasing).
I hope I'm making some sense. I'll try to spend some time rewriting this.
In addition, I'll integrate answers to any questions that come as a result
of this mess!
PL : Previous Level value
NL : Next Level value
INITIAL LEVEL SETTING
PL = 0
OPEN INPUT FILE FOR READING
WHILE NOT EOF (Y DIMENSION: FOR EACH LINE)
GENERATE NEW PATTERN
SET PATTERN PTR TO BEGINNING OF PATTERN
OUTPUT FULL PATTERN
WHILE NOT EOL (X DIMENSION: FOR EACH POSITION)
NL = NEXT INPUT LEVEL VALUE
IF NL != PL (IF WE'RE CHANGING LEVELS)
IF NL > PL (IF WE'RE MOVING UP)
DELETE NEXT NL-PL BITS IN PATTERN FROM PTR FORWARD
(IF GOING FROM LEVEL 0 TO 2, DELETE 2 BITS IN PATTERN)
ELSE (IF MOVING DOWN, AWAY)
INSERT PL-NL RANDOM BITS INTO PATTERN AT PTR POSITION
(IF GOING FROM LEVEL 3 TO 2, INSERT 1 BIT INTO PATTERN)
PL = NL (UPDATE PL)
OUTPUT NEXT VALUE IN PATTERN
ELSE
OUTPUT NEXT VALUE IN PATTERN
ADVANCE PATTERN PTR (CIRCULAR PATTERN)
ADVANCE INPUT PTR
(Redundancy exists to simplify readability.)
Assuming spaces translate to level 0, input like this (thanks, Dave
Thomas):
22222222222222222 11111111111111111111111
2222222222222222222 11111111111111111111111
22222222222222222222 11111111111111111111111
22222 22222 11111
22222 22222 11111
22222 22222 11111
22222 22222 11111
22222 22222 11111
22222 22222 11111
22222222222222222222 11111
2222222222222222222 11111
22222222222222222 11111
Yields output like this:
Co6&`R(D(v"i`<$$Co6&`R(D(v"i`<$$Co6&`R(D(v"i`<$$Co6&`R(D(v"i`<$$Co6&`R(D
mwBy&>`,QFdZ<$wamwBy&>`,QFdZ<$wamwBy&>`,QFdZ<$wamwBy&>`,QFdZ<$wamwBy&>`,
7Z,o:.sw5[rHt&{:7Z,osw5[rHt&{:7Z,osw505[rHt&{:7Zosw505[rHt&{:7Zosw505[rR
g"EzQy{lW_3C&B[8g"Ez{lW_3C&B[8g"Ez{lW_3S3C&B[8g"z{lW_3S3C&B[8g"z{lW_3S3y
yiQ?fiVF!G{TAtrJyiQ?VF!G{TAtrJyiQ?VF!G{T]TAtrJyi?VF!G{T]TAtrJyi?VF!G{T]s
1`I|r?FLoB#<sf!Q1`I|FLoB#T#<sf!Q1`ILoB#TaT#<sf!Q1`ILoB#Ta#<sf!#Q1`ILoB#T
m$LuSD0hh7\qy5:nm$Lu0hh7\x\qy5:nm$Lhh7\x"x\qy5:nm$Lhh7\x"\qy5:-nm$Lhh7\x
[#7hrqKUm`/<bic$[#7hKUm`/7/<bic$[#7Um`/7r7/<bic$[#7Um`/7r/<bick$[#7Um`/7
L,'O)X\L&Xu)ZUw(L,'O\L&Xu|u)ZUw(L,'L&Xu|y|u)ZUw(L,'L&Xu|yu)ZUwy(L,'L&Xu|
3`#YPTdg:,;rmy9`3`#Ydg:,;(;rmy9`3`#g:,;(7(;rmy9`3`#g:,;(7;rmy94`3`#g:,;(
1w^N7d;f964U,yml1w^N;f964&4U,yml1w^f964&;&4U,yml1w^f964&;4U,ym{l1w^f964&
<>Y8igID(]?"A0+;<>Y8ID(]?"A0+;<>Y8ID(]?"?"A0+;<>Y8ID(]?"?A0+;<O>Y8ID(]?"
eRl5hfJx.cD0tscheRl5Jx.cD0tscheRl5Jx.cDeD0tscheRl5Jx.cDeDtscheiRl5Jx.cDe
v,r7f6%<)R-AaV^hv,r7%<)R-AaV^hv,r7%<)p)R-AaV^hv,r7%<)p)R-aV^hv>,r7%<)p)R
VbWqd^]qi(IRW)ytVbWqd^]qi(IRW)ytVbWqd^]qi(IRW)ytVbWqd^]qi(IRW)ytVbWqd^]q
`^Y-z8v=[gBX(Aqq`^Y-z8v=[gBX(Aqq`^Y-z8v=[gBX(Aqq`^Y-z8v=[gBX(Aqq`^Y-z8v=
This uses 16 as the Max pattern size. Notice on the third line of the
output (the first line with level changes), the pattern is "7Z ... &{:".
When we go from level 0 to level 2, we lose two characters (i.e., ":.").
When we go from level 2 back to level 0, we insert two new characters
(i.e., "05" after the "osw5").
Any questions? Or better yet, what did I leave out?? I do hope this helps
someone!?!
-----------------------------------------------------------------------
----- C CODE TO GENERATE TEXT STEREOGRAMS -----------------------------
-----------------------------------------------------------------------
Also from Dave Thomas:
Now here's a hack of a hack I found on the net. Basically it generates
stereograms from ascii diagrams. Here's the program first (it uses the
lookback algorithm, not the stored-pattern algorithm described above):
##define DEPTH0 16
##define COLS 79
##include <stdio.h>
main()
{
long now;
int col;
char m[COLS+1],s[COLS+1];
int i,e,c;
/* seed random number generator */
time (&now);
srand (now);
/* print fusion X's */
for (col = 0; COLS - col >= DEPTH0; col += DEPTH0)
{
for (i = 0; i < DEPTH0-1; ++i)
putchar (' ');
putchar ('X');
}
putchar ('\n');
/* process input image */
while (memset(m,'\0',COLS+1),fgets (m, COLS+1, stdin))
{
e = 0;
s[COLS] = 0;
for(i=0; i<COLS; )
{
e = 0;
while (i >= DEPTH0 && i < COLS &&
(c = m[i - DEPTH0]) >= '0' && c <= '9')
{
e = 1;
s[i] = s[i-DEPTH0+c-'0'];
++i;
}
s[i++] = (e || i < DEPTH0) ? randasc() : s[i-DEPTH0];
}
puts (s);
}
}
randasc()
{
/* large set of random characters */
return ('!'+rand()%92);
/* lowercase random letters */
/* return ('a'+rand()%26); */
}
Try passing it this file as the standard input:
22222222222222222 11111111111111111111111
2222222222222222222 11111111111111111111111
22222222222222222222 11111111111111111111111
22222 22222 11111
22222 22222 11111
22222 22222 11111
22222 22222 11111
22222 22222 11111
22222 22222 11111
22222222222222222222 11111
2222222222222222222 11111
22222222222222222 11111
You'll get output like this:
X X X X
"i`<$$Co6&`R(D(v"i`<$$Co6&`R(D(v"i`<$$Co6&`R(D(v"i`<$$Co6&`R(D(v"i`<$$Co6&`R(D
dZ<$wamwBy&>`,QFdZ<$wamwBy&>`,QFdZ<$wamwBy&>`,QFdZ<$wamwBy&>`,QFdZ<$wamwBy&>`,
rHt&{:7Z,o:.sw5[rHt&{:7Z,osw5[rHt&{:7Z,osw505[rHt&{:7Zosw505[rHt&{:7Zosw505[rR
3C&B[8g"EzQy{lW_3C&B[8g"Ez{lW_3C&B[8g"Ez{lW_3S3C&B[8g"z{lW_3S3C&B[8g"z{lW_3S3y
{TAtrJyiQ?fiVF!G{TAtrJyiQ?VF!G{TAtrJyiQ?VF!G{T]TAtrJyi?VF!G{T]TAtrJyi?VF!G{T]s
##<sf!Q1`I|r?FLoB#<sf!Q1`I|FLoB#T#<sf!Q1`ILoB#TaT#<sf!Q1`ILoB#Ta#<sf!#Q1`ILoB#T
\qy5:nm$LuSD0hh7\qy5:nm$Lu0hh7\x\qy5:nm$Lhh7\x"x\qy5:nm$Lhh7\x"\qy5:-nm$Lhh7\x
/<bic$[#7hrqKUm`/<bic$[#7hKUm`/7/<bic$[#7Um`/7r7/<bic$[#7Um`/7r/<bick$[#7Um`/7
u)ZUw(L,'O)X\L&Xu)ZUw(L,'O\L&Xu|u)ZUw(L,'L&Xu|y|u)ZUw(L,'L&Xu|yu)ZUwy(L,'L&Xu|
;rmy9`3`#YPTdg:,;rmy9`3`#Ydg:,;(;rmy9`3`#g:,;(7(;rmy9`3`#g:,;(7;rmy94`3`#g:,;(
4U,yml1w^N7d;f964U,yml1w^N;f964&4U,yml1w^f964&;&4U,yml1w^f964&;4U,ym{l1w^f964&
?"A0+;<>Y8igID(]?"A0+;<>Y8ID(]?"A0+;<>Y8ID(]?"?"A0+;<>Y8ID(]?"?A0+;<O>Y8ID(]?"
D0tscheRl5hfJx.cD0tscheRl5Jx.cD0tscheRl5Jx.cDeD0tscheRl5Jx.cDeDtscheiRl5Jx.cDe
-AaV^hv,r7f6%<)R-AaV^hv,r7%<)R-AaV^hv,r7%<)p)R-AaV^hv,r7%<)p)R-aV^hv>,r7%<)p)R
IRW)ytVbWqd^]qi(IRW)ytVbWqd^]qi(IRW)ytVbWqd^]qi(IRW)ytVbWqd^]qi(IRW)ytVbWqd^]q
BX(Aqq`^Y-z8v=[gBX(Aqq`^Y-z8v=[gBX(Aqq`^Y-z8v=[gBX(Aqq`^Y-z8v=[gBX(Aqq`^Y-z8v=
-----------------------------------------------------------------------
----- HOPE FOR THE HOPELESS :-) ---------------------------------------
-----------------------------------------------------------------------
From: wchaga@vela.acs.oakland.edu (William C. Haga)
Being one who has used wide-eyed vision on chain link fences ever
since I was a kid, I was able to see the images in SIRDS right
away. But I've had difficulty explaining the technique to friends.
Today I had the latest Games magazine with me at my parents house.
Games is running another contest using SIRDS, so there are three in
the latest issue. This time I thought of the reflection idea. So I
opened mom's china cabinet, put the magazine against the glass in
the door, and told mom to keep looking at her own reflection in the
glass until the image appeared.
It took less than thirty seconds.
When she saw the 3d train engines, I was subjected to a squeal of
delight that I hadn't heard from her for a long time. "EEK! IT'S
COMING OUT AT ME! IS THIS EVER NEAT!". Dad tried for about a minute
but gave up.
About an hour later, mom and I heard a shout. We went to
the dining area, and there was dad with the magazine against the
glass in the door. "Isn't that just the most amazing thing!", said he.
Later they were making jokes about teaching old dogs new tricks.
-----------------------------------------------------------------------
----- COMMERCIAL Stereogram Producers --------------------------------------
-----------------------------------------------------------------------
Infix Technologies
PO Box 381
Orem, UT 84057-0381
(801) 221-9233
contact: John M. Olsen, jolsen@nyx.cs.du.edu
18x24 Earth (mercator projection of the Earth's altitudes)
18x24 Salt Lake LDS Temple Centennial
18x24 Beethoven (300 DPI! Very smooth.)
(others are coming soon, too.)
Retail price for the 18x24 inch prints is $20 plus $3 s/h. Utah residents
add 6.25% sales tax. Wholesale and distributor discounts are available.
Quotes for custom work are also available. Cost and minimum order varies,
based on content.
Altered States
92 Turnmill St,
Farringdon,
London, EC1, U.K.
+44 (0)71 490 2342
Paul Dale (P.A.Dale@bath.ac.uk)
tel: +44 (0)225 826 215
Send a catolog request to:
N.E. Thing Enterprises
19C Crosby Drive
Bedford, MA 01730
>Info from: Neal T. Leverenz (at802@yfn.ysu.edu)
Inner Dynamics, Inc.
The distributor: Privileged Traveler
4914 Brook Road
Lancaster, OH 43130
(614) 756-7406
Retail prices stated below plus $3 S&H. Ohio residents add 5.5% sales tax.
GLOW IN The DARK Poster Series - $23 (size: 18" X 24")
"Knight Vision" - suspended chess board with chess pieces
above the board in daylight viewing - also an area in the center that has
a Knight chess piece - random dot pattern glows and is viewable in the dark!!
Premium Color Series - $16 (size: 18" X 24")
"Gecko" - twin Gecko lizards
"I Think Therefore I Am" - well known quote surrounded by stunning visuals
"SoulMate" - hearts, spirals, and other symbols, for that special person
"The Mighty Unicorn" - unicorn, mystical castle, wizard, and flying dragon
"Excalibur" - legendary sword in the stone, castle, knights, etc.
"Where's Wilbur?" - can you find him in the forrest?
Optimum Series - $15 (size: 24" X 36", black and white)
"Beyond Reality" - hearts, spirals, other cool shapes - extremely detailed
"20/20 Third Sight" - an eye chart done in 3D
"Illusions" - a labyrinth, try to find your way out!
"Meditation" - contains an ancient mandala, a real stress buster
"DreamWeaver" - unusual geometric shapes, helps induce lucid dreaming and
dream remembrance
"Icons" - the five symbols of life
"Rainbows" - see color on a black and white poster (Not a 3D poster)
>Sam Weaver (sew@cblpd.att.com)
*
Todd D. Hale * * * *
thale@novell.com * *
halet@bert.cs.byu.edu