Have you walked through a mall lately? These days, as you wander past most of the poster shops, there will be a large group of people staring at the same poster with surprisingly weird expressions on their faces. Some will be in the initial stages of denial or rejection---they will be concentrating, some slowly rocking their heads backwards and forwards, searching for an image that they have never seen before. Others will be grinning from ear to ear, pointing at the poster, chuckling with their friends that a member of their group hasn't seem them yet. "Come on Bill, come on!", they cry and as Bill gets increasingly more frustrated he concentrates harder and harder, until finally (if he's lucky) he sees a true 3D image, without the need for special glasses or equipment.

These pictures are known as Single Image Random Dot Stereograms (SIRDS), or Single Image Stereograms (SIS) depending on whether the picture contains random dots as a base for the 3D effect, or a repetitive pattern. Unfortunately, each commercial company has labelled them differently. Shop owners generally don't know what you mean, unless you say "Hollusion" or one of the many other specific names.

Stereogram Mechanism

What is a stereogram ?

In this document I refer to stereogram (though, single image stereogram would be more correct) as being something like the image that follows:

To understand the mechanism which allows you to get this peculiar effect, we should take a look at the process of vision.

The feeling of "depth" that you get by looking at a statue instead of looking at a photo of the same statue, is due to the fact that the human body has two eyes.

In the above example with the statue, we need just one eye to get the general shape of the statue. A humble photo does the same. It is the second eye that provides some "extra" information. This extra information is the "depth" of the various parts of the statue. In fact a "photo" gives just a bi-dimensional (x,y) representation, to get the third dimension (z) you need some "extra".

                y
                 |       |---------
                 |    z  | Photo  |
                 |    /  |        |
                 |  /    ---------|
                 |/_______ x

In fig.1 we assume that there are 2 objects, X and Y which are at the same height (y) and different depths (z) and positions (x)

|--------------------------------------------------|
|                                           Fig.1  |
|                                    z             |
|                               y    |             |
|          Y                      \  |             |
|                                   \|_____x       |
|                                                  |
|                                                  |
|                                                  |
|                                                  |
|                                                  |
|        X                             ^           |
|                                      |           |
|                                      |           |
|                                      |           |
|            (o)     (o)                           |
|                                   watching       |
|        left-eye  right-eye        direction      |
|                                    (depth)       |
|--------------------------------------------------|

(fig.2L -left eye, fig.2R -right eye; the '+' marks the center of each picture)

|--------------------------| |-------------------------|
|                   Fig.2L | |                  Fig.2R |
|                          | |                         |
|                          | |                         |
|                          | |                         |
|      X Y +               | |  X       Y   +          |
|                          | |                         |
|                          | |                         |
|                          | |                         |
|                          | |                         |
|--------------------------| |-------------------------|

shift.X = d.hrz.right ( X, '+') - d.hrz.left ( X, '+')

shift.Y = d.hrz.right ( Y, '+') - d.hrz.left ( Y, '+')

where "dx.hrz.hhh ( A, '+')" means distance (on the horizontal axis) in the hhh picture from object A to origin/center.

Furthermore, with good approximation we can say that any objects with the same 'shift' are at the same "depth" (z)

In the same way, the eyes forward to the brain two slightly different pictures. It is the brain that must "compute" a 3-D representation of the scene. The difficulty is to know which pairs must be associated to "compute" the z-coordinate. In the example above it's easy to assume that the 'X' from each picture is associated to one 'X' object. The same goes for the two 'Y'. But the images that the brain gets to compute, can be quite complicated. What if there are more X-s and Y-s in each picture ? How does the brain establish the "couples" for which to calculate the shift/depth ? A clue is that each pair must be on the same height (y). Which means that the brain should not try to associate spots, patterns that are located at different heights. But that is not enough !

The 'brain' can make mistakes in this process of designation of pairs! It is that which make possible the 3-D feeling that we get from stereograms.

The simplest stereogram that we can get is something like-this:

      
________________________________________________________
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|    *        *        *        *        *        *    |
|------------------------------------------------------|
Col:1    2        3        4        5        6        

In fig.3 (Left/Right) I have represented the kind of pictures that the eyes forward to the brain when looking at the preceding stereogram. (notice '+', the center)

|----------------------------||--------------------------|
| :    :    :    :    :Fig.3L||:    :    :    :   Fig.3R:|
| :    :    :    :    :    : ||:    :    :    :    :    :|
| :    :    :    :    :    : ||:    :    :    :    :    :|
| :    :    :    :    :    : ||:    :    :    :    :    :|
| :    :   +:    :    :    : ||:    :    :    :    +    :|
| :    :    :    :    :    : ||:    :    :    :    :    :|
| :    :    :    :    :    : ||:    :    :    :    :    :|
| :    :    :    :    :    : ||:    :    :    :    :    :|
| :    :    :    :    :    : ||:    :    :    :    :    :|
|----------------------------||--------------------------|
column:
  1L   2L   3L   4L   5L   6L  1R   2R   3R   4R   5R   6R

1L-1R, 2L-2R, 3L-3R, 4L-4R, 5L-5R, 6L-6R

but it can happen that the brain does the following association:

1L-2R, 2L-3R, 3L-4R, 4L-5R, 5L-6R, ?-1R, 6L-?

Remember: All columns look alike !

Of course it is possible that the brain makes other associations of these kinds:

1L-3R, 2L-4R, 3L-5R,... or 2L-1R, 3L-2R, 4L-3R,... etc.

It can be noticed that by choosing a diferent association of columns the "shift" between the images of the objects changes. As a result the "depth" of the perceived objects changes. In the association 1L-2R, 2L-3R,... the shift is reduced -> the "depth" increases -> the columns seem somewhere behind.

Is it possible to determine exactly the power of the brain in matching complicated images ? I thought, some time ago, what would happen if we put someone in front of a large panel situated at a convenient distance (so that the eyes are relaxed) and the panel is full of randomly disposed spots. The spots should be all alike and in very great number, very small but big enough to not became a uniform gray. The brain should be overwhelmed by the great number of matches that it must try. What will happen ? The person will get dizzy ? get a headache ? Or will the person be forced to see just a gray fog ?

Different types of images:

Autostereogram: Original name for a SIRDS

RDS: Random Dot Stereogram

SIRDS: Single Image Random Dot Stereogram

SIRTS: Single Image Random TEXT Stereogram (also known as ascii stereograms)

Stereogram: This is a general, simplified term for SIRDS and SIRTS (occasionally stereo-pairs)

Different viewing actions:

Wall-eyed: Converging eyes past the actual image

Cross-eyed: Converging in front of the image

Infinity-focus: Forcing your eyes' lines of sight to be parallel (not necessary for wall-eyeing SIRDS)

Most Stereogram pictures are usually generated so that if you look at (converge your eyes on) a position twice as far away as the picture, and focus on the picture, generally after a few minutes you see a surprising 3D image!

Most people find this extremely difficult for the first time. You have to focus on a point which is different from where you are looking. This is known as "de-coupling" your vision process. Instinctively people focus at the same point they are looking at, and this is the main obstacle in seeing images of this type.

This is why most posters come with a reflective surface such as glass or plastic covering them---if you try to look at your reflection you will be looking at a point twice as far away as the actual poster. It has been noted by almost everyone that while this sometimes helps beginners see the 3D effect for the first (and perhaps even the first few) times, experienced viewers to not need any help like this, and indeed the reflection is usually very distracting and decreases the quality of the 3D effect.

There are many ways to teach this de-coupling to either yourself or to others, including (in almost no particular order):

NOTE: It is generally easier to see Stereograms under bright light. I have been told this is because you eye relies less on focus under harsh conditions. Another point, to see stereo images, you need to have "passable" use of both eyes. If you wear glasses try with and without them on. Some short-sighted people can see them easier without their glasses on (if they get closer to the picture).

The pull-back

Hold the picture (or move your face) so your nose is touching the picture. Most people than can not possibly focus with something this close to their eyes, and they will be content with their inability to focus. With the picture up close, pretend that you are looking straight ahead, right through it. Now slowly pull the picture (or your face) away while keeping your eyes pointed straight ahead. If you do this slow enough, an image usually appears when the picture is at the correct distance.

The reflection

As mentioned above, with a reflective surface it is sometimes a lot easier to converge your eyes in the correct position. You simply focus on your nose or some central reflection in the picture, and wait until you focus on the image.

The drunk-eyes

This method is used to describe the feeling of the process of deconverging your eyes. It is very much like being drunk or having "staring-eyes". Your eyes don't look at the object, but rather through it. This state is common to some in the morning before the coffee caffine fix.

The wall, or the finger

Hold the picture so that it is half between you and a wall. Look *over* the top of the picture towards the wall, and focus on something such as a picture hook or mark. While keeping this "gaze" either slowly lift the picture or lower your eyes while keeping them converged on the wall.

A similar approach (but for cross-eyed viewing) is to stand arm's length away from the picture and put your finger on the picture. While slowly pulling your finger towards your face, keep looking at your finger, you will notice the picture becoming blurry, and at an intermediate position you will (eventually) see the 3D image.

The see-through

If it is possible, photocopy the picture onto a transparency. Then focus through the transparency onto something twice as far away. This is similar to (The wall, or the finger) above except now you don't need to change the position of your gaze.

Cheating...

To cheat, photocopy the image onto two transparencies, then overlay them and carefully shift them horizontally so they are about an inch or two out of alignment. Somewhere around this position you will see a rendition of the image. Obviously in 2D not 3D, but you will at last finally believe there is "somethere in there."

For those who do not have a local SIRDS distributor (i.e., the poster cart at the mall), here are a few companies you may be able to order from.

------------- Infix Technologies -------------

$20 Earth (mercator projection of the Earth's altitudes)
$20 Salt Lake LDS Temple Centennial
$20 Beethoven (300 DPI! Very smooth.)

These prints are 18x24 inches. 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.

PO Box 381
Orem, UT 84057-0381,USA
Ph: (801) 221-9233
email: John M. Olsen (jolsen@nyx.cs.du.edu)

------------- Inner Dynamics, Inc. -------------

(Distributors)
Privileged Traveler
4914 Brook Road
Lancaster, OH 43130, USA
(614) 756-7406

Glow in the Dark Poster Series - $22 (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!!

"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 forest?

"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; very stunning visuals

"Rainbows" - see color on a black and white poster (Not a 3D poster)

Retail prices (USA) stated above plus $3 S&H (USA) - call for overseas S&H. Ohio residents add 5.5% sales tax.

------------- 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

------------- N.E. Thing Enterprises -------------

Send a catolog request to:
N.E. Thing Enterprises
19C Crosby Drive
Bedford, MA 01730, USA.
-- info from: Neal T. Leverenz (at802@yfn.ysu.edu)

Books

"Principles of Cyclopean Perception"
(c) 1972 by Bela Julesz,
MIT press. Considered by most as the original work oPn Random Dot Stereograms:
-- Charles Eicher (CEicher@Halcyon.com)

"Magic Eye: A New Way of Looking at the World"
(c) 1993 by N.E. Thing Enterprises.
Andrews and McMeel, A Universal Press Syndicate Company
Kansas City, USA. 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)

"Magic Eye II: Three Dimension Trip Vision"
(c) 1992 by N.E. Thing Enterprises/Tenyo Co., Ltd.
Korean Translation (c) 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)
They've taken the technique a step further by applying the pseudo-random patterns as noise superimposed over another image. You look at the pages of this book and see one image, then cross your eyes and concentrate on the replicated patterns in the background noise and see the second image. It's kinda cute.
-- Robert Reed

"Das magische Auge" (German version of "Magic Eye")
(c) 1994, arsEdition, Munich
ISBN 3-7607-8297-3
DM 29,- (seen at a store for this price)

"Stereo Computer Graphics and Other True 3D Technologies"
(c) 1993, David F. McAllister, Ed.
Princeton University Press
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)

"Random Dot Stereograms"
(c) 1993, Kinsman Physics, P.O. Box 22682, Rochester, NY 14692-2682, USA.
An excellent source of information (sample RDS and source code)
-- Eric Thompson (E.Thompson@ncl.ac.uk)
ISBN 0-9630142-1-8
US$ 13.95

"Human Stereopsis. A psychological Analysis"
(c) 1976, W.L. Gulick and R.B. Lawson,
Oxford University Press.

Papers

R.I. Land and I.E. Sutherland, (1969) "Realtime, color, stereo, computer displays" Applied Optics, 8(3): 721-723; March

D. Marr and T. Poggio, (1976) "Cooperative computation of stereo displarity" Science, 194: 283-287; October 15

D. Marr and T. Poggio, (1979) "A computational theory of human stereo vision" Proceedings Royal Society of London, B204: 304-328 Science, 194: 283-287; October 15

G.S. Slinker and R.P. Burton, (1992) Journal of Imaging Science and Technology, 36(3): 260-267; May/June

D. G. Stork and C. Rocca, (1989) "Software for generating auto-random-dot stereograms", Behavior Research Methods, Instruments, and Computers 21(5): 525-534.

H.W. Thimbleby and C. Neesham, (1993) "How to play tricks with dots" New Scientist, 140(1894): 26-29; October 9

For people without graphics displays, or simply like having a 3D .signature, you can create a stereo effect using repetitive characters.

Text Stereograms (not random)

-- the following by Dave Thomas (dthomas@bbx.basis.com)

-- the next few are by DR J (me90drj@brunel.ac.uk)
Look for his new upcoming Text Stereogram Guide---out soon!

1962

Julesz, B. and Miller, J. E. (1962) Automatic stereoscopic presentation of functions of two variables. Bell System Technical Journal. 41:663-676; March. Thimbleby (1990) refers to this article: "Julesz and Miller were the first to show clearly that a sense of depth could arise purely from stereopsis, without relying on other cues such as perspective or contours. they used random patterns of dots which, although meaningless to single eye viewing, nevertheless created a depth impression when viewed in a stereoscope."

The following additional information about Julesz seems to be from The Magic Eye, 1993, N.E. Thing Enterprises, Andrews and McMeel. I found it quoted in a newspaper article:

During the 1960s, a researcher named Bella Julesz was the first to use computer-generated 3-D images made up of randomly placed dots to study depth perception in human beings. Because the dot pictures did not contain any other information, like color or shapes, he could be sure that when his subject saw the picture it was 3-D only.

In the years that followed, other people continued using random dot pictures in their work; many of them were graduate students who studied with Julesz. With time they found new and better ways to create these interesting illusions.

1965

Bela Julez, "Textured and Visual Perception," Scientific American, Feb. 1965. An article on stereo dot pictures. [George J Valevicius]

1966

N. A. Valyus. Stereoscopy. Focal Press, London and New York. 426 pp. (I have not seen this book, but Boyer,1990 refers to it to say that Stereographic paintings are almost beyond possibility.)

1968

Bela Julez. "Experiment in Perception," Psychology Today, July 1968. Cover story with a full page graphic and a few smaller ones.

1971

Bela Julesz. Foundations of Cyclopean Perception. Chicago: Univ. of Chicago Press. I have not seen this book, but Kinsman,1992 mentions it: "Julesz (1971) describes photographic techniques producing random dot stereograms in use in the early 1950s.... Since Julesz, in 1960, was the first to employ a computer to generate random dot stereograms, many would consider him the person most responsible for their popularity today.... Anaglyphs of random dot stereograms... are presented in the back of Julesz's book, and a pair of the (half-red/half-green) glasses required to view them is tucked inside the back cover."

1971

Dr. Bella Julesz in "Reading from Scientific American - Image, Object and Illusion" by W.H. Freeman Publisher ISBN 0-7167-0505-2 (1971). [Bob Easterly]

1976

Marr, D. and Poggio, T. (1976), Cooperative computation of stereo disparity, Science, 194:283-287; October 15. Thimbleby (1990) refers to this article: "[They] discuss computational models of the visual processes that are involved in interpreting random dot stereograms."

1977

Bela Julesz. Foundations of Cyclopean Perception. University of Chicago Press, Chicago. xiv, 406 pp. I assume this is the same book as the 1971 book referenced by (Kinsman,1992). I think Boyer gave the wrong publication date. Of the book, Boyer writes:

"The random-dot stereogram is a very inspiring demonstration of the sophistication and complexity of the information-processing which occurs in everyday human vision.... The first extensive studies of random-dot stereograms were accomplished by Bela Julesz and his colleagues on large and expensive computers, using professional programmers, at the Bell telephone Laboratories." (Boyer,1990)

1977

Tyler & Chang, Vision Research, #17. Referenced by Tyler, 1983.

1979

Marr, D. and Poggio, T. (1979), A computational theory of human stereo vision, Proceedings Royal Society of London, B204, 304:328. Thimbleby (1990) refers to this article: "[They] discuss computational models of the visual processes that are involved in interpreting random dot stereograms."

1983

Schor & Cuiffreda, editors. Vergence Eye Movements: Basic & Clinical Aspects. One chapter, by Christopher Tyler including genuine SIRDS. Interestingly, he doesn't say he invented them. He just calls them "a new type of autostereogram designed for free fusion without the need for a stereoscope or anaglyph glasses". Then he says the basis is the repetition of a random pattern and refers to Tyler & Chang, 1977, Vision Res, #17. [Dan Richardson]

1985

Paul S. Boyer. Stereographic technique for illustrating geologic specimens. New Jersey academy of Science, Bulletin, volume 39, no. 2, pp. 83-91. I have not seen this article, but Boyer,1990 refers to it when speaking of the DIN 4531 stereogram format.

1986

L. L. Kontsevich. "An Ambiguous Random-Dot Stereogram Which Permits Continuous Changing of Interpretation," Vision Research, Vol. 26, No. 3, pp. 517-519. I have not seen this article, but Kinsman,1992 mentions it: "Kontsevich (1986) describes a technique for making a series of tiles." Kinsman presents a "similar stereogram" that is a SIRDS. If so, this would be the first SIRDS I am aware of.

1987

Paul S. Boyer. Constructing true stereograms on the Macintosh. The Journal of Computers in Mathematics and Science Teaching, volume 6, no. 2, pp. 15-22. (I have not seen this article, but Boyer,1990 refers to it as a detailed article describing computer stereography.)

1988

Falk, Brill and Stork produce the "Seeing The Light" image that Dyckman referenced in his Stereo World article. [Dan Richardson]

1988

J. Ninio and I. Herlin. "Speed and Accuracy of 3D Interpretation of Linear Stereograms, Vision Research, Vol. 28, No. 11, pp. 1223-1233. I have not seen this article, but Kinsman,1992 mentions it: "Ninio and Herlin (1988), and Slinker and Burton (1992), experimented with stereograms containing complex patterns [triangles, lines, blotches, and even images] in their initial noise fields."

1989

Rocca and Stork, Behavior Research Methods, Instruments and Computers, 1989, might be vol 21 number 5. Demonstrats a little Mac program they wrote to generate SIRDS from MacPaint files. [Dan Richardson]

1990

Paul S. Boyer, Professor of Geology, Fairleigh Dickinson University, "Random-Dot Stereograms -- Creating a Psychological Phenomenon," STEREO WORLD, March/April 1990. Creating SIRDS on the Mac.

1990

Tyler, C. W. and Clarke, M. B. (1990) The autostereogram. SPIE Stereoscopic Displays and Applications 1258: 182-196. Thimbleby (1990) refers to this article: "Recently, however, Tyler and Clarke realized that a pair of random dot stereograms can be combined together, the result being called a single image random dot stereogram (SIRDS) or, more generally, an autostereogram.... [They] described a simple but asymmetric altorithm, which meant, for example, that some people can only see the intended effect when the picture is held upside-down."

1990

Dan Dyckman, "Single Image Random Dot Stereograms," STEREO WORLD, May/June 1990. "I was recently surprised when a friend of mine ... showed me a random-dot-stereograph that consisted fo a single image, rather than the usual stereo pair. To view the image, one fused two marks within the image, and would see the words SEEING THE LIGHT."

"Interested readers might consider creating poster-sized images using this technique, or experimenting with supplementary gray-level or color values for each pixel. And, if any reader knows who invented this technique for single image random dot sstereograms, or who created the SEEING THE LIGHT image, please drop a note to this magazine."

1991

Prior to June 1991 a company named Pentica Systems, Inc (One Kendall Square, Building 200, Cambridge, MA 02139, Tel. 617-577-1101, Tom Baccei - President) published an advertisment, "Pentica Loves Puzzles," with a SIRDS image in it. The magazine may have been EDN--I don't remember.

1991

About June 3, 1991, Pentica mails an information packet to those responding to the add. In the information Pentica sent to those responding to the ad, they say, "We discovered ... the technique for generating it in STEREO WORLD." Four SIRDSs accompany the information, marked "images (c) 1990 by Dan Dyckman."

1991

June 13, 1991, N.E. Thing Enterprises, (One Kendall Square, Building 200, Cambridge, MA 02139) also mails a flyer to those responding to the Pentica ad. The N.E.Thing address and the Pentica address are the same, as well as the postal meter number (FMETER 8010560) for the two mailings. The flyer states, "from the people who created the Pentica Loves Puzzles Ad.... Because of the unbelievably enthusiastic response to our random dot stereogram featured in the 'Pentica Loves Puzzles' ad, we are rushing you this advance notice of our latest 3D mindbenders." They offered 3 posters, World's Hardest Maze, The Third Eye, Training Wheels, and a 1992 Calendar.

1992

Andrew A. Kinsman, Random Dot Stereograms, Kinsman Physics, 1992. First printing October 1992. "This history of the stereogram is a bit elusive. It appears to be intertwined with anaglyphs, lenticular photographs, and stereoscopic photographic techniques. Charles Wheatstone described stereoscopy in 1832. In 1851 the the London Society of Arts held the Crystal Palace Exhibition, which six million people attended and potentially witnessed Sir David Brewster demonstrate the stereoscope. Stereoscopes became popular as a result. Kahn (1967), in The Codebreakers, references an article by Herbert C. McKay, written in the late 1940s, on how to manufacture simple stereograms with a typewriter for encryption purposes.... Julesz (1971) describes photographic techniques producing random dot stereograms in use in the early 1950s. History seems to have recorded no particular inventor of stereograms. It is quite probable that soon after parlor-style stereoscopes became popular someone took a photograph of a camouflaged hunter with a stereo camera. The subject in the resulting picutre might be difficult to identify. Viewed stereoscopically with the rest of their collection, the subject would become obvious."

1992

"This unique synthesis of computer technology and fine art began simply as an idea between two creative individuals in 1992. Paul's art background and Mike's computer genious proved to be the perfect combination of talents. Several hundred man hours later, in a remote region of California, came the first public exposure to Holusion(TM) 3D Prints. And so NVision Grafix was born." (NVision Grafix flyer introducing Calypso Reef, 1993.) "Micro Synectic was Mike Bielinski is NVision...NE Thing and Micro Synectics are listed in the StareEO demo, because Mike Bielinski wrote it for NE Thing." (CompuServe messages from Dan Richardson) "The images are the creation of NVision Grafix, a Texas-based firm owned by two former fraternity brothers, Paul Herber and Mike Bielinski. They developed the Holusion technology while making a poster of the B-2 bomber for the company where Herber worked as an engineer. The posters were a huge hit, and soon, Herber and Bielinski had abandoned their jobs to start up NVision: Herber is the artist, and Bielinski is the computer whiz.... As NVision has grown, though so has it's competition. Computer expert Tom Baccei has created his won "high-tech, three-dimensional art form" under the name "Magic Eye" and is marketing the images on books, posters, calendars, puzzles and cards." (Nicole Brodeur, Orange County Register. As reprinted in The Daily Herald, March 22, 1994)

1993

N.E. Thing begins patent process on several RDS algorithms. "Salitsky dot" algorithm and the algorithm to produce an RDS that looses it's colors when viewed in 3D are apparently two algorithms. I have not seen the patent applications, but the law requires that they discuss "prior art." If someone could get copies of these applications, it would not only describe the algorithms in detail, it would present a history of SIRDS, to the degree that N.E. Thing was aware.

1993

Harold W. Thimbleby, Stuart Inglis, and Ian H. Witten, "Displaying 3d Images: Algorithms for Single Image Random Dot Stereograms," University of Waikato, Hamilton, New Zealand, published on the Internet. I believe Stuart mentioned it was being published in an IEEE journal in 1994. I've forgotten which one and when. [IEEE Computer, soon - S.]

Is it possible to generate a stereogram such that the image is dependent on the viewing rotation?

The short answer is YES! In a "normal" stereogram the constraints are only in the horizontal direction, but by assigning constraints in 2-dimensions instead of linearly across the image, it is possible. I believe the first time I saw this was an image by Tyler [to be referenced].

--comment by John Olsen to Andrew Steer(follows)
>Also I think it should be possible to create a stereogram which gives
>TWO images: one when viewed landscape and another when looked at
>portrait. It would however only be possible for certain patterns
>and NOT in general (your average real image or logo).

Typically, you can only do a small image, entirely contained in the first copy of the random buffer (50 pixels wide in your case). The "vertical" image is repeated, but it gets more and more distorted as you go across the page.

There are, as you say, limited things you can do which cover greater areas, but the limitations are rather severe. The quality of the results depends on how much error you're willing to put up with, as "fog" and uncertainty in the resulting image if you want both vertical and horizontal to be full page images.

Can you "tile" or "wallpaper" stereograms?

--from the net
Some people say YES!, others say NO!

Is it possible to see two *completely* different images by alternating between the "wall-eyed" and "cross-eyed" techniques?

By using complementary colors for the left and right eye, is it possible to create a stereogram in which the 3D image "loses" it's color and appears in greyscale?

Yes! It can be done. Would anyone like to elaborate on this matter? :-)

From: zcapl31@ucl.ac.uk (William Andrew Steer)
Newsgroups: alt.3d
Subject: Constructing SIRDS, Windows source code MK1
Summary: Most basic program to draw SIRDS, written in C++ for Windows
Date: Tue, 31 May 1994 11:06:20 GMT

This is about the simplest Windows program for drawing SIRDS. It is only bare-bones, you'll have to modify the program for alternative depth sources, and the SIRDS is reconstructed from scratch after every WM_PAINT message ie whenever the window is resized or uncovered. Use CTRL+ALT+DEL to exit while it's drawing.

If you don't program in C, just look at the TMyWindow::Paint function. You should be aware that the random(arg) function returns an integer between 0 and arg-1.

If you have Turbo C++ then make a copy of one of the example project files in the /tcwin/owl/examples subdirectory, and copy the program below to your /examples subdirectory. Open Turbo C++, load the new project, and change it's contents to include just the program below and OWL.DEF. It should then run ok.

[-- later comments by Andrew Steer
I would like to stress that it uses the 'lookback' algorithm, which has some limitations, namely:
- it assumes that the right eye looks perpendicular to the screen while the left eye looks slightly sideways (so the rays converge), when in reality both eyes should look inwards. This causes asymmetry in the image (which according to some sources makes it more difficult for some people to see) and results in near objects appearing marginally further right than far ones.]

I have since developed algorithms for linear depth, and improved Z-resolution. I'll post the program tomorrow [dated Tue, 31 May 1994].

// ObjectWindows SIRDS Program (C)W.A. Steer 1994
//                              email: w.steer@ucl.ac.uk
// Simplest routine possible
//
// 


// Picture not stored
// - is completely redrawn for each WM_PAINT


#include < owl.h >
#include < math.h >


const pattwidth=96;  // the basic repeat distance.
// On a 14" monitor and 640x512 display, 96 pixels
// represents about half the distance between the eyes.
                     
const NumColors=4;


// Define the colors to use in form 0xbbggrrL
//  0x  signifies hex notation
//  bb  blue value, gg  green value, rr  red value
//  L tells the compiler the constant is Long ie 32bit

COLORREF cols[NumColors]=
{
 0x000000L,
 0x800000L,
 0xFF0000L,
 0x000080L
};



// ----------------  TMyWindow  ----------------

class TMyWindow : public TWindow
{
public:
 TMyWindow( PTWindowsObject AParent, LPSTR ATitle);

 virtual void Paint( HDC PaintDC,
                     PAINTSTRUCT& PaintInfo );
};


TMyWindow::TMyWindow( PTWindowsObject AParent,
                     LPSTR ATitle) :
              TWindow(AParent, ATitle)
{
 Attr.W=620;  // Set the default window size to 620x340
 Attr.H=330;
}


void TMyWindow::Paint(HDC PaintDC, PAINTSTRUCT& )
{
 int pixels[700];

 int x,y;
 int h;    // height of 'features' above the background
 int l,pl; // lookback and previous lookback distances

 long r,s; // temporary storage for constructing sphere


 for (y=0; y<300; y++)
 {
  for (x=0; x<PATTWIDTH; 
  ((y if sphere the on point a of height Calculate 
   background with flush is image default by h="0;" 
   { x++) x<612; (x="pattwidth;" for pl="pattwidth;" }
   pixels[x]="random(NumColors);">=36) && (y<=164))
   {
    r=64*64-(y-100L)*(y-100L);
    if (r>0)
    {
     s=r-(x-256L)*(x-256L);
     if (s>0) h=sqrt(s)+64;
    }
   }

   // Calculate the lookback distance
   l=(int)(pattwidth-h/8.0+0.5);

   // if image has got deeper (new lookback is greater
   //  than old lookback distance) generate a new pixel,
   // otherwise repeat an old one
   if (l>pl)
    pixels[x]=random(NumColors);
   else
    pixels[x]=pixels[x-l];

   pl=l;
  }

  // Copy the image to screen
  for (x=0; x<612; x++)
  {
   // use the colors defined at the top in cols[]
   // if you're not using Windows don't worry about
   // PaintDC parameter
   SetPixel(PaintDC,x,y,cols[pixels[x]]);
  }
 }
}



// ----------------  TMyApp  ----------------

class TMyApp : public TApplication
{
public:
 TMyApp(LPSTR AName, HINSTANCE hInstance,
   HINSTANCE hPrevInstance, LPSTR lpCmdLine,
     int nCmdShow)
   : TApplication(AName, hInstance, hPrevInstance,
      lpCmdLine, nCmdShow) {};

 virtual void InitMainWindow();
};


void TMyApp::InitMainWindow()
{
 MainWindow = new TMyWindow(NULL, Name);
}                      


int PASCAL WinMain(HINSTANCE hInstance,
  HINSTANCE hPrevInstance, LPSTR lpCmdLine,
    int nCmdShow)
{
 TMyApp MyApp("Original SIRDS by W.A.Steer",
    hInstance, hPrevInstance, lpCmdLine, nCmdShow);
 MyApp.Run();
 return MyApp.Status;
}

-- William C. Haga (wchaga@vela.acs.oakland.edu)

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.

STW_DEMO.EXE: the full package will allow RDS creation
Approx US$40
N.E.Thing Enterprises
P.O. Box 1827
Cambridge, MA 02139, USA.
Config: DOS

STEREOLUSIONS: creater/render/print SIRDS
I/O Software, Inc.
Ph: (909/483-5700 800/800-7970), USA.
Config: WINDOWS/Windows NT
(From William Saito, 3/07/94)

KAI's POWER TOOLS: Photoshop add-on for SIS creation
Config: MAC

To see a stereogram you must converge your eyes in such a fashion that each eye is looking at the corresponding pixel/dot required to get the 3D effect.

If you are converging your eyes in front of the picture instead of behind the picture, you will see the apparent image inverted.

This is what you should be doing:

    right    left
     (.)      (.)
      \        /
       |      |
       \      /
        |    |
.....pixel..pixel......(actual picture/poster)
        \    /
         |  |
         \  /
         |  |  
          \/
           |
          XX(perceived position in 3D--behind the object
 

    right    left
     (.)      (.)
      \        /
       \      /
        \    /
         \  /
          \/
          XX  (perceived position in 3D in front
          /\                      of the object)
         /  \
        /    \
       /      \
      /        \ 
     /          \ 
..pixel........ pixel......(actual picture/poster)
 

From: jolsen@nyx10.cs.du.edu (John Olsen)
Newsgroups: alt.3d
Subject: Call for stereograms
Date: 26 May 1994 22:16:33 -0600

A stereogram distributor has asked me to post the following info. Please don't contact me about it. Call or write (snail mail) to him. Tell him you saw my message on the Internet.

----
David Sterling, president of Sterling Crescent International, Inc. is looking for commercial-grade stereograms to be included in books and as postcards. He prefers groups of images to singles, and you must be the original designer (owner of the copyright on the image).

Payment on accepted designs will be on a royalty basis. For an upcoming book deal, he is trying to get all images submitted in final form by the end of June. The postcard work is ongoing.

I'd suggest calling him once you have a list of titles together, and then working out how to get preview copies to him (disk, paper, fax...). He's been distributing stereogram materials for a long time (long for the stereogram business, anyway :^), so he's picky about high quality, good detail, and eye-catching patterns.

He is:

David Sterling

Sterling Crescent International, Inc

PO Box 690253

San Antonio, TX 78269, USA

voice (210) 558-7143

fax (210) 558-7144