leech@piglet.cs.unc.edu (Jonathan Leech) (01/27/89)
All this discussion about 3D leads me to wonder how widely people
vary in their ability to perceive different types of 3D. For example,
several years ago I was taught how to use a stereo microscope to
search for asteroids. The idea was to make an image from two plates of
the same part of the sky taken 15 minutes apart. The stars would not
move, but any asteroids would move slightly.
The stereo effect was supposed to make asteroids stand out from
the flat starfield. As it happened, they did not seem to stand out
very much for me, and I reverted to using it as a blink microscope
instead (good exercise for the eye muscles :-) Do many people have
this type of problem?
--
Jon Leech (leech@cs.unc.edu) __@/
SUSHIDO: the Way of the Tunathant@horus.SGI.COM (Thant Tessman) (01/28/89)
In article <6382@thorin.cs.unc.edu>, leech@piglet.cs.unc.edu (Jonathan Leech) writes: > > All this discussion about 3D leads me to wonder how widely people > vary in their ability to perceive different types of 3D. [stuff deleted] > Do many people have > this type of problem? > -- > Jon Leech (leech@cs.unc.edu) __@/ > SUSHIDO: the Way of the Tuna An excelent book on stereo is "Foundations of the Stereoscopic Cinema" by Lenny Lipton. It mentions that stereo viewing devices don't work on about eight percent of the population. Thant Tessman thant@sgi.com
po0o+@andrew.cmu.edu (Paul Andrew Olbrich) (01/28/89)
(in response to using stereo views to check for asteroids...) > The stereo effect was supposed to make asteroids stand out from > the flat starfield. As it happened, they did not seem to stand out > very much for me, and I reverted to using it as a blink microscope > instead (good exercise for the eye muscles :-) Do many people have > this type of problem? > -- > Jon Leech (leech@cs.unc.edu) __@/ > SUSHIDO: the Way of the Tuna I noticed that I seem to be somewhat better than average at understanding 3D relationships. In a high school geometry class, for example, I remember being rather surprised when the teacher had a hard time drawing a cube on the blackboard as a 2D projection, (even without perpective) ... I even figured out how to do a similar projection of a 4D hypercube in 2D, and once made a 3D projection of a 4D hypercube out of toothpicks. (This had no forth-dimensional "perspective" ... It was essentially two cubes, one offset diagonally with the corresponding verticies connected by toothpicks. If you make one of these and do it well, it creates some neat effects that I noticed by accident. I had it placed on a table, and once I was walking by and glanced over at it, and noticed that it had collapsed. The cubes seemed to be both flat on the table, lying ajacent to each other. In reality, it was just my viewing angle making them look that way! Everything lined up and fooled my vision. After more experimentation I realized that from the correct angle it looks like two cubes stacked vertically. Also, viewed "edge on" it looks like a single cube. Later I noticed that if I placed it on a polished surface, and viewed it from the two stacked cubes point of view, the reflection was of a single cube only. From the "one cube" point of view, the reflection was two cubes. This is fun at parties!) I also wrote a hypercube simulation program (ideas taken from Sci Am) that did rotation in real time (after calculating the screen coordinates for about up to 30 seconds before each rotation). It did 4D perspective so it was a more "realistic" (yeah, right) model than the toothpick one. Rotating through a 4D axis is hard to visualize at first, but I found that I really had a good mental idea of what was happening. I attempted to do a red/blue 3D glasses version, so that I could essentially have a 3D projection (with 4D perspective) model, but I was doing it on a vintage IBM PC and the colors didn't match up. Whatever. - Drew --- Drew Olbrich po0o+@andrew.cmu.edu "A brush that does not work is not a brush." -- me
u-jmolse%sunset.utah.edu@wasatch.UUCP (John M. Olsen) (01/29/89)
In article <25652@sgi.SGI.COM> thant@horus.SGI.COM (Thant Tessman) writes: >An excelent book on stereo is "Foundations of the Stereoscopic Cinema" by >Lenny Lipton. It mentions that stereo viewing devices don't work on about >eight percent of the population. >Thant Tessman thant@sgi.com Does it follow that this 8% also lacks depth perception under normal conditions? Say, driving down the freeway? Now that's a spooky thought. /\/\ /| | /||| /\| | John M. Olsen, 1547 Jamestown Drive /\/\ \/\/ \|()|\|\_ |||.\/|/)@|\_ | Salt Lake City, UT 84121-2051 \/\/ /\/\ | u-jmolse%ug@cs.utah.edu or ...!utah-cs!utah-ug!u-jmolse /\/\ \/\/ "A full mailbox is a happy mailbox" \/\/
jwl@ernie.Berkeley.EDU (James Wilbur Lewis) (01/29/89)
In article <985@wasatch.UUCP> u-jmolse%sunset.utah.edu.UUCP@wasatch.UUCP (John M. Olsen) writes: -In article <25652@sgi.SGI.COM> thant@horus.SGI.COM (Thant Tessman) writes: - ->It mentions that stereo viewing devices don't work on about ->eight percent of the population. - -Does it follow that this 8% also lacks depth perception under normal -conditions? Say, driving down the freeway? Now that's a spooky thought. No, it doesn't follow -- binocular stereo is only one of many cues used by the visual system for depth perception. Close one eye -- does the world look flat now? No -- you still have parallax, motion, and size constancy cues to give you a fairly good 3-D percept. -- Jim Lewis U.C. Berkeley
ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab) (01/29/89)
In article <6382@thorin.cs.unc.edu> leech@piglet.UUCP (Jonathan Leech) writes: >For example, several years ago I was taught how to use a stereo microscope to >search for asteroids. [ ... ] Funny, I use a telescope :-). (Don't panic; I know what he means.) > The stereo effect was supposed to make asteroids stand out from >the flat starfield. As it happened, they did not seem to stand out >very much for me, and I reverted to using it as a blink microscope >instead (good exercise for the eye muscles :-) Do many people have >this type of problem? Just as some people are colorblind, there are some people who are stereoblind. I have a bit of trouble seeing stereo (which is odd, considering that I worked on what turned out to be decent 3D software and images on the Amiga). The problem is not uncommon, and the way I compensate for it is by swapping eyes and observing if the left-right shifts are correct. Unless you interact with artificial 3D on a daily basis, I personally don't think it's much to worry about, since there are a zillion other depth cues your brain can use. 3D isn't just whatever a book tells you; it's psychological, too, and as such it's tricky stuff. What looks good to one person could look completely wrong to someone else. That's probably why the asteroid searching method didn't quite work for you. Of course, bad 3D (like the StuporBowl ad) will always look bad. _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ Leo L. Schwab -- The Guy in The Cape INET: well!ewhac@ucbvax.Berkeley.EDU \_ -_ Recumbent Bikes: UUCP: pacbell > !{well,unicom}!ewhac O----^o The Only Way To Fly. hplabs / (pronounced "AE-wack") "Work FOR? I don't work FOR anybody! I'm just having fun." -- The Doctor
cosell@bbn.com (Bernie Cosell) (01/30/89)
In article <985@wasatch.UUCP> u-jmolse%sunset.utah.edu.UUCP@wasatch.UUCP (John M. Olsen) writes: }In article <25652@sgi.SGI.COM> thant@horus.SGI.COM (Thant Tessman) writes: } }>An excelent book on stereo is "Foundations of the Stereoscopic Cinema" by }>Lenny Lipton. It mentions that stereo viewing devices don't work on about }>eight percent of the population. } }>Thant Tessman thant@sgi.com } }Does it follow that this 8% also lacks depth perception under normal }conditions? Say, driving down the freeway? Now that's a spooky thought. I'm one of those people. I'll spare you an anecdote-filled autobiography but I can note several things: a) stereoscopy is only one of a fair number of visual cues that a person uses to figure out 3D relationships. A person can learn to do fine using just the others [I'm also a pilot --- now *that* was interesting: learning to land without depth perception. not scary, not impossible, just took a bunch of practice] b) I'm told (how could I verify?!) that stereo-vision is mostly useless for large scale problems like driving. That is, when the question is "is that fifty feet away or 250 feet away", stereo vision just tells you "far away" and you have to use other cues (just the same ones I do) to pinpoint whether it is time to step on the brakes or not. Where true stereo vision seems to be MOST useful (again, I'm told...:-) :-() is in CLOSE UP work. I have a tiny bit of trouble picking things up: when I reach across a table to grab a glass of water, if I'm not careful, I'll "miscalculate" the distance by a 1/4"... which is oftenthe difference to knocking the #@$%^@# thing over and grabbing it. c) I have very limited stereo vision: I can enjoy stereo slides (and own a Realist camera). What most people don't understand is that stereo slides are, for the most part, NOT lifelike for me. On the contrary: I find going to movies MUCH more of an experience than, apparently, stereo-sighted people do. Movies have _most_ of the cues I normally use in place, and those are what I use to construct the 3D world ALL THE TIME. Hence, movies look very much like real world to me. And, on the other hand, I can stare at a 3D slide of something spectacular for a fair length of time, fascinated, since it *doesn't* look like that in "real life" to me, and it is fun actually seeing things "leap out". The superbowl was a bust for me: I can do a little bit of stereo fusing if things cooperate and just SIT there (as in a slide)... moving images are hopeless.... hope you folks enjoyed it! :-( d) In response to the other poster (I forget who) who responded to a question about stereo vision with anecdotes about 3D visualization. Well, I assume he was guessing that a person with no stereo vision would be living in "flatland" and constantly be amazed that things disappear when they go around a corner or some such. This is not the case (as he could have figured out by being a smidgeon more introspective: since he was able to "understand" a bit about the fourth dimension, even though he can't perceive it AT ALL for the most part, it doesn't take stereo vision to "figure out" how our 3D world works). Not having stereo vision is an inconvenience, but not really a handicap. __ / ) Bernie Cosell /--< _ __ __ o _ BBN Sys & Tech, Cambridge, MA 02238 /___/_(<_/ (_/) )_(_(<_ cosell@bbn.com
lishka@uwslh.UUCP (Fish-Guts) (01/30/89)
In article <cXsBOzy00XoZM0ml5i@andrew.cmu.edu> po0o+@andrew.cmu.edu (Paul Andrew Olbrich) writes: > > I noticed that I seem to be somewhat better than average at >understanding 3D relationships. In a high school geometry class, for example, I >remember being rather surprised when the teacher had a hard time drawing a cube >on the blackboard as a 2D projection, (even without perpective) ... I've noticed that different people can have wildly different abilities to "view" and "understand" 3D relationships. A (somewhat) practical anecdote: Here at the U. of Wisconsin, there is a series of three courses in calculus that most science students take. The first course covers integration/differentiation; the second starts with Taylor Series and ends with 3D geometry; the third continues with 3D geometry and ends with diff-EQ's. I had a miserable time trying to understand the "normal" calculus topics, but when it came to 3D geometry, I did remarkably well (straight A's in the 3D geometry, C's or lower in the other topics). However, most people in the class seemed to do the exact opposite: had an easy time with the calculus, but were incredibly confused by the 3D geometry. All of my friends (with the exception of one who aced all the topics) fell into the latter category. In fact, 3 of my friends effectively *quit* taking calculus because they had such a hard time with the 3D geometry at the end of the 2nd course. This experience led me to believe that people's ability to "visualize" or "understand" 3D topics (i.e. rotations, differentiating in multi-dimensional spaces, visualizing 4D, etc.) varies quite a bit. I am not sure why, though. Any other thoughts/experiences in this area? .oO Chris Oo. -- Christopher Lishka ...!{rutgers|ucbvax|...}!uwvax!uwslh!lishka Wisconsin State Lab of Hygiene lishka%uwslh.uucp@cs.wisc.edu Immunology Section (608)262-1617 lishka@uwslh.uucp "I'm not aware of too many things... I know what I know if you know what I mean" -- Edie Brickell & the New Bohemians
efrethei@afit-ab.arpa (Erik J. Fretheim) (01/30/89)
How to spot us non 3D'ers: 1. Scuffed up shoe toes. 2. Sometimes miss what we're grabbing at. 3. Walk down 6 stairs when there are only 5. 4. Avoid ball sports. 5. Play badmiton better when inebriated.
cab@opus.ATT.COM (C. Anthony) (01/31/89)
In article <414@uwslh.UUCP>, lishka@uwslh.UUCP (Fish-Guts) writes: > In article <cXsBOzy00XoZM0ml5i@andrew.cmu.edu> po0o+@andrew.cmu.edu (Paul Andrew Olbrich) writes: > > > > I noticed that I seem to be somewhat better than average at > >understanding 3D relationships. > > I've noticed that different people can have wildly different > abilities to "view" and "understand" 3D relationships. A (somewhat) > practical anecdote: > Visualizing all the dimensions, and translating between them is a breeze for me....up till the fourth dimension (tm). The closest I've come Is conceiving of a universe in which all stages of the universes evolution simultaneously co-exist, and you can flip back and forth between them. sort of like video still frame, where you can go to the previous and next frames. In a "Look and Feel"(tm) way this seems accurate to me, but mathematically, you just can't plug it into equations. *Look and Feel is a trademark of Apple computer :-), anyone using the term "Look and Feel" to describe the look and feel of anything will be prosecuted. Anyone looking or feeling without the written consent of Apple Computer Co., will be liable for damages proportional to the pleasure derived from looking and feeling. :-), :-) -- -CAB- _____/ _ || _\___ lNYCl_ ______ __|) Standard disclaimer. == (0) (0)
jjc@sun1.MAYO.EDU (Jon Camp) (02/01/89)
1) As Benie Cosell posted, 3-D perception is much more than stereopsis. It involves parallax, focus, accomodation, obscuration, perspective, memory, a great many other functions which I am not aware of and most likely some that no one has ever measured. In our everyday lives, stereopsis is not even the primary means of depth perception. Stereopsis IS, however, relatively inexpensive to simulate, and is therefore the only contact most people have with "3-D display". 2) Early studies of stereopsis indicated that as many as 30% of the population were "stereo-blind". More recent studies put the figure closer to 10%. I have never heard the 80% figure before, and I doubt that we would see stereo effects (of ANY quality) on broadcast TV if that were the case. Our own informal survey of employees at the BRU (mostly medical imaging people, but a few secretaries, administrators and technicians as well) found only one "stereo-blind" individual out of 30 tests - he had only o ne good eye. We note that the earlier studies required the subjects to make the depth/no depth decision very quickly whereas we allowed our coworkers to take as much time as they needed - so MAYBE **WARNING - unfounded wild theory ahead *** there is more than one mechanism of stereo perception, some instantaneous, some requiring the use of memory. 3) The common wisdom is that stereopsis is most effective within the reach of our hands. My personal experience is that this is true. I suspect it is possible to prove that beyond a certain distance it is physically impossible for our visual apparatus to sense any difference between left and right views. 4) As one who has experience viewing stereo and other 3-D representations, I wish to report that stereopsis alone gives me a sensation of "viewing fatigue", possibly because stereo so vividly presents SOME depth cues while perversely witholding others. This is a personal experience, NOT a rigorous criticism of stereoptic display. This is more than enough for a posting, but I can talk indefinitely about perception, display, graphics, imaging, (man,woman,life,death,infinity...) and will if anyone cares to continue this by email. Jon J. Camp - Free advice, worth the price. 3-D Display Group Biodynamics Research Unit Mayo Foundation jjc@bru.mayo.edu
jbn@glacier.STANFORD.EDU (John B. Nagle) (02/01/89)
In article <1104@nic.MR.NET> jjc@sun1.UUCP (Jon Camp) writes: > >1) As Benie Cosell posted, 3-D perception is much more than stereopsis. It >involves parallax, focus, accomodation, obscuration, perspective, memory, a >great many other functions which I am not aware of and most likely some >that no one has ever measured. In our everyday lives, stereopsis is not >even the primary means of depth perception. Stereopsis IS, however, >relatively inexpensive to simulate, and is therefore the only contact >most people have with "3-D display". This subject has been studied in some detail by developers of flight simulators. See "Flight Simulation", by J.M Rolfe and K.J. Staples, ISBN 0-521-35751-9, section 7.2, "The Psychophysics of Visual Perception". They identify eight main non-binocular cues of distance, which I will not give here. I do recommend this book to anyone involved in the generation of realistic imagery. >3) The common wisdom is that stereopsis is most effective within the reach >of our hands. "Flight Simulation" references T. Gold, 1972, "The Limits of Stereopsis For Depth Perception in Dynamic Visual Situation", Society for Information Display, International Symposium, Digest of Technical Papers, who reports that stereopsis dominates differential size and motion parallax out to about 17m (64m if the observer fixates his eyes on the moving object.) This is with the observer moving at about 0.5m/sec. Faster movement brings the limit closer. This is somewhat beyond the reach of the hands, and in fact stereo vision systems have been built for in-flight refueling simulators. >4) As one who has experience viewing stereo and other 3-D representations, >I wish to report that stereopsis alone gives me a sensation of "viewing >fatigue", possibly because stereo so vividly presents SOME depth cues >while perversely witholding others. This is a personal experience, NOT a >rigorous criticism of stereoptic display. Viewing fatigue for 3D imagery is a serious problem. The phenomenon is moderately well understood, and has been written up in technical papers of the SMPTE, from the point of view of understanding how to make 3D movies. When viewing images that are not in the same scale as real life, some rather strict rules must be followed to avoid visual fatigue. Unfortunately, I don't have the paper around, but it was by someone in Hollywood who provides 3D gear to filmmakers. One useful gadget they offer is a pocket calculator preprogrammed with the calculations needed to set up a shot for 3D. For close-ups, this is non-trivial. They also offer a special leader for 3D films that allows the projectionist to align the system properly. Failure to do this correctly will induce headaches in some of the audience. John Nagle
len@csd4.milw.wisc.edu (Leonard P Levine) (02/01/89)
From article <1104@nic.MR.NET>, by jjc@sun1.MAYO.EDU (Jon Camp): > 1) As Benie Cosell posted, 3-D perception is much more than stereopsis. It involves parallax, focus, accomodation, obscuration, perspective, memory, a great many other functions which I am not aware of and most likely some that no one has ever measured. In our everyday lives, stereopsis is not even the primary means of depth perception. Stereopsis IS, however, relatively inexpensive to simulate, and is therefore the only contact most people have with "3-D display". If you watch animals that do not normally have 3D perception like rabbits and such, the move their heads up and down a bit while looking at things. I am sure (not scientificially) that this permits the animal to view things in 3D. Perhaps checking with one-eyed people will show that they also move their heads when looking at things. + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + | Leonard P. Levine e-mail len@evax.milw.wisc.edu | | Professor, Computer Science Office (414) 229-5170 | | University of Wisconsin-Milwaukee Home (414) 962-4719 | | Milwaukee, WI 53201 U.S.A. Modem (414) 962-6228 | + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
ritter@versatc.UUCP (Jack Ritter) (02/01/89)
In article <25652@sgi.SGI.COM>, thant@horus.SGI.COM (Thant Tessman) writes: > In article <6382@thorin.cs.unc.edu>, leech@piglet.cs.unc.edu (Jonathan Leech) writes: > > > > All this discussion about 3D leads me to wonder how widely people > > vary in their ability to perceive different types of 3D. > > [stuff deleted] > > > Do many people have > > this type of problem? > > -- > > Jon Leech (leech@cs.unc.edu) __@/ > > SUSHIDO: the Way of the Tuna > When I was in video games, I wrote a 3d game. It was on a color vector system. I split the screen into left & right images. The images were integrated by means of a parascope mirror system. Objects in each half were draw in perspective. Thus 3 ques were used: perspective, triangulation, & motion. The game was first person: driving along a road & shooting things. 3d explosions were like totally gnarly. Most people enjoyed the effect. A few actually DID NOT perceive the 3d, even though their eyes superimposed the 2 halves correctly. Beats me how they missed it. (I should acknowledge my co author: Earl Stratton). -- -> Even aliens think The Three Stooges are funny. <- Jack Ritter, S/W Eng. Versatec, 2710 Walsh Av, Santa Clara, CA 95051 Mail Stop 1-7. (408)982-4332, or (408)988-2800 X 5743 UUCP: {pyramid,mips,vsi1,arisia}!versatc!ritter
sfisher@abingdon.SGI.COM (Scott Fisher) (02/01/89)
In article <60@opus.ATT.COM>, cab@opus.ATT.COM (C. Anthony) writes: > > Visualizing all the dimensions, and translating between them is a > breeze for me....up till the fourth dimension (tm). The closest I've come > Is conceiving of a universe in which all stages of the universes evolution > simultaneously co-exist, and you can flip back and forth between them. > sort of like video still frame, where you can go to the previous and next > frames. Not a bad analogy. Some computer animation packages let you do just such a thing--manipulate the object in 4D just as a solid modeller lets you in 3D or a paint program does in 2D. It's not quite as grandiose as your conception, but it's a good way to demonstrate one possible fourth dimension. And of course... there is a fifth dimension, beyond those we know. It is... oh, nevermind.
sdutcher@netxcom.UUCP (Sylvia Dutcher) (02/01/89)
In article <690@csd4.milw.wisc.edu> len@csd4.milw.wisc.edu (Leonard P Levine) writes: >If you watch animals that do not normally have 3D perception like rabbits >and such, the move their heads up and down a bit while looking at things. Cats have no depth perception and move their heads to judge distances, but this doesn't give them 3D perception. When you move your head like this, thing that are closer move differently than things that are far away. >I am sure (not scientificially) that this permits the animal to view things >in 3D. Perhaps checking with one-eyed people will show that they also >move their heads when looking at things. I have two eyes, but no depth perception. I didn't know about this until an eye exam some years ago. I'm not good at sports that involve hand-eye coordination (lik baseball) but am able to drive a car, etc. I suppose I adapted to this lack in my childhood. There have been occasions, when I am in unfamiliar surroundings, that I have been aware of my lack of depth perception. It's very strange to see a person walk behind a pillar that you expected them to pass in front of! >+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + >| Leonard P. Levine e-mail len@evax.milw.wisc.edu | >| Professor, Computer Science Office (414) 229-5170 | >| University of Wisconsin-Milwaukee Home (414) 962-4719 | >| Milwaukee, WI 53201 U.S.A. Modem (414) 962-6228 | >+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + -- Sylvia Dutcher * The likeliness of things NetExpress Communications, Inc. * to go wrong is in direct 1953 Gallows Rd. * proportion to the urgency Vienna, Va. 22180 * with which they shouldn't.
po0o+@andrew.cmu.edu (Paul Andrew Olbrich) (02/02/89)
John Camp writes: > As one who has experience viewing stereo and other 3-D representations, I wish > to report that stereopsis alone gives me a sensation of "viewing fatigue", > possibly because stereo so vividly presents SOME depth cues while perversely > witholding others. This is a personal experience, NOT a rigorous criticism of > stereoptic display. I have a similar problem, but I think it's due to the fact that the vision in my right eye isn't perfect (things get fuzzy at about four feet away) but my left eye is 20/20. Under normal circumstances I really don't notice this because my good eye compensates completely. I don't wear glasses or contacts. As someone mentioned earlier, most stereoscopic 3D vision effects occur within a few feet of your eyes. Outside that range, the two images your eyes send back to your brain are almost identical. When I watch a 3D movie, obviously, the 3D effects occur on the screen, which is beyond the "clear vision" range of my right eye. So half of what I see is blurry, just as usual, but now my brain is being told to attempt to extract a 3D image from a blurry and non-blurry image. Normally it never has to do this because the two images fed to it to produce 3D are both clear (because they're close.) In a standard movie, there's just one image that both eyes share ... one's fuzzy, and I guess my brain just ignores it. Just an idea, anyway .. I don't know how accurate that is. 3D movies are usually somewhat annoying to watch though. Oops ... In the above, I was remembering the first 3D movie that I saw, which was a B-rate sci fi flick using polarized glasses. About two years ago, I saw another one at Epcot Center (in Disney World). I remember that it wasn't nearly as troublesome to watch and that I enjoyed it a lot more, visually speaking. Maybe more care was taken in the filming or something ... I also have rediculously light-sensistive blue eyes, see well in the dark, and really hate being outside without sunglasses during mid-summer ... I can't look more than a few degrees above the horizon without having to turn away. Two summers ago I remembering trying the play volleyball and really having a hard time of it because I didn't have sunglasses on ... Nobody else seemed to mind the sun. That's not important for 3D, though, I suppose. Comments welcome ... - Drew -- Drew Olbrich po0o+@andrew.cmu.edu
ciemo@bananapc.SGI.COM (Dave Ciemiewicz) (02/02/89)
In article <25867@sgi.SGI.COM>, sfisher@abingdon.SGI.COM (Scott Fisher) writes: > In article <60@opus.ATT.COM>, cab@opus.ATT.COM (C. Anthony) writes: > > > > Visualizing all the dimensions, and translating between them is a > > breeze for me....up till the fourth dimension (tm). The closest I've come > > Is conceiving of a universe in which all stages of the universes evolution > > simultaneously co-exist, and you can flip back and forth between them. > > sort of like video still frame, where you can go to the previous and next > > frames. > > Not a bad analogy. Some computer animation packages let > you do just such a thing--manipulate the object in 4D just > as a solid modeller lets you in 3D or a paint program does > in 2D. It's not quite as grandiose as your conception, but > it's a good way to demonstrate one possible fourth dimension. > > And of course... there is a fifth dimension, beyond those > we know. It is... oh, nevermind. > > I'm familiar with the Fifth Dimension. They were a musical group from the early seventies. One of their most popular hits was "Age of Aquarius." Me, I'm a Taurus. -- Dave (commonplace) "Boldly going where no one cares to go." Ciemiewicz (incomprehensible) ciemo (infamous)
beres@cadnetix.COM (Tim Beres) (02/04/89)
In article <6382@thorin.cs.unc.edu> leech@piglet.UUCP (Jonathan Leech) writes: > > All this discussion about 3D leads me to wonder how widely people >vary in their ability to perceive different types of 3D.... 3D, what's that. I've known for many years, and a couple of eye operations, that my 3D abilities were/are impaired. A month ago I went in for an eye exam, and the doc gave me a 3D perception test that I don't think I've ever had before. I was supposed to see one number stand out in a row of numbers. When I looked I thought he was kidding. Absolutely zero 3D perception. My condition is called, variously: Leading eye, non-binocular vision, no depth perception, etc. The weird thing is, I've compensated for the problem. No problems with catch or any other eye coordination stuff. The super bowl effects were noticable, however. Tim (and my right eye just sorta follows along) ------>MY SOAPBOX (I speak for myself) My nephew Mark, in a letter: Hi Uncle Tim my aquarium is great. 4 fish died but my crab is still living. [Some of us have good attitudes] Tim Beres beres@cadnetix.com {uunet,boulder,nbires}!cadnetix!beres
beres@cadnetix.COM (Tim Beres) (02/04/89)
In article u-jmolse%sunset.utah.edu.UUCP@wasatch.UUCP (John M. Olsen) writes: > >Does it follow that this 8% also lacks depth perception under normal >conditions? Say, driving down the freeway? Now that's a spooky thought. > See my earlier posting (I'm one of them 8%). What happens is that you learn to compensate for the problem - in fact you don't really know you have a problem. You just pick out different visual cues. Note that in high school I was a 3rd baseman and all-conf. wide receiver. Though, I admit, I'm not as comfortable driving at night (never had a night accident though - just a day one). Tim (now where did I put my car keys, that trip to Snowbird is about to begin :-) ------>MY SOAPBOX (I speak for myself) My nephew Mark, in a letter: Hi Uncle Tim my aquarium is great. 4 fish died but my crab is still living. [Some of us have good attitudes] Tim Beres beres@cadnetix.com {uunet,boulder,nbires}!cadnetix!beres
raveling@vaxb.isi.edu (Paul Raveling) (02/07/89)
In article <oXtpycy00Uo1Q5VkYK@andrew.cmu.edu> po0o+@andrew.cmu.edu (Paul Andrew Olbrich) writes: > >As someone mentioned earlier, most stereoscopic 3D vision effects occur within a >few feet of your eyes. Outside that range, the two images your eyes send back >to your brain are almost identical. ... This seems sensible, but I often notice fairly strong stereoscopic vision in woodsy mountains, looking at things such as 500 foot hills half a mile away. Which brings up a related question... I seem to perceive stereo lots better when looking at something that's generally green, like those woodsy hills or nearby bushes, than when looking at other colors. Is there a correlation between stereo and color, or do I just have an affinity for trees and bushes? --------------------- Paul Raveling Raveling@vaxb.isi.edu
LadyHawke@cup.portal.com (Classic - Concepts) (02/10/89)
> I was supposed to see one number stand out in a row of numbers.
Be careful!!! This doesn't NECESSARILY mean you have no depth-perception. I t
took a similar test in which one number was
supposed to stand out in a row of numbers. My 3d visualization and depth
perception are reported to be excellent but I flunked totally on that one.
You see, not all tests purported to measure depth-perception are actually
in 3d! Some are illusions created with shape or colors or other cues we
are familiar with. The test you describe and the one I took may fall into
this category. In my case what I saw was little green outlines to one side
of each letter. Now, to someone with normal or '20/20' vision, perhaps
one looks closer due to the illusion, but to me (I have way above average
vision; it was 20/13 and 20/15 at the time of the test) all I saw was little
fine lines around the letters. None appeared to be closer until the very
last one when I blurred my vision out of sheer nervousness and frustration
and voila! one of the letters popped forward! But only if I squinted or
severely blurred the images. I almost didn't get my driver's license based on
that. Consequently I wouldn't trust some of those tests, particularly if
they are ones based on the illustion of 3d. jxh@cup.portal.com (Jim - Hickstein) (02/19/89)
While we're on the subject of human visual perception, specifically stereopsis, has anyone else noticed that their *perception* of 3-d, not just stereopsis, occasionally "goes flat", especially when under stress of, say, sleep deprivation? I have several times experienced driving along a "projected" road, that is, projected on a flat screen in front of my (moving) car. Once I managed (suffered?) quite a long episode of this, over half an hour. One friend of mine, upon hearing that I had had this experience, was much relieved to know that he wasn't losing his marbles: he, too, had experienced this. Now, I don't scour the medical literature, so maybe this "astereopsis" (a misnomer, I now realize) is common; yet, I haven't heard more than this one other report. How many of you have had this experience? How long does it last? Can you make it come and go at will (I'm approaching this)? Is it related to stress, or visual fatigue? I gather that a significant number of readers share my habit of voluntary sleep deprivation, related to their work: are you a programmer, or do you often stay up late for some reason? Does watching TV or reading (close-up tasks) exacerbate or trigger this condition? (Contrast my half hour tour-de-force in the car; luckily the road was quite empty.) I find that reading with one eye closed (face distorted due to propping head on bent arm) triggers it after about half an hour. (I get lots of practice with reading in bed: I'm almost through my chemistry text, which I seldom see in 3-d :-). Also, my new prescription sunglasses (80 per cent, color neutral) cause a temporary loss of steropsis (not 3-d perception entirely) when I put them on. I gather this has something to do with how they grind lenses these days, and what, precisely, is the density of the lens along the viewing axis at a given instant; I have been told that if the two lenses are not precisely the same density (i.e. a sidelong glance) that an illusion occurs related to stereopsis. I have seen this at the Exploratorium in the "Professor Pulfrich's Universe" exhibit, but I'm not convinced this is the reason I have trouble: after a few minutes acclimatization, the effect is gone and I can drive normally. Let's hear from those of you with prescription sunglasses, too. -Jim Hickstein jxh@cup.portal.com ...!sun!portal!cup.portal.com!jxh
po0o+@andrew.cmu.edu (Paul Andrew Olbrich) (02/21/89)
This is in reply to Jim Hickstein's earlier comment about losing stereoscopic effect ... Never happened to me, but one thing that does happen to me (and other people I've talked to) is a wierd sensation that everything's suddenly shrunk down an order of magnitude, even though it really looks the same. This happens very infrequently ... once every few months or so. Usually it occurs after I've been staring at a book for a long time, or at a computer screen. It always occurs at night, but I usually am not staying up extremely late when it happens. Usually I get the sensation that I'm atop a very tall building looking down at everything. It's very odd to look down at your own body and still feel that way. I try to shake it off by putting my hands right in front of my face but it usually doesn't work. A simple change of scenery, like getting up and walking to the kitchen, usually dispells the effect. -- Drew Olbrich po0o+@andrew.cmu.edu "Company's coming. Better clean this mess up." -- Kurt Vonnegut
bader+@andrew.cmu.edu (Miles Bader) (02/21/89)
po0o+@andrew.cmu.edu (Paul Andrew Olbrich) writes: > Never happened to me, but one thing that does happen to me (and other > people I've talked to) is a wierd sensation that everything's suddenly > shrunk down an order of magnitude, even though it really looks the same. > This happens very infrequently ... once every few months or so. Usually > it occurs after I've been staring at a book for a long time, or at a > computer screen. It always occurs at night, but I usually am not staying > up extremely late when it happens. Usually I get the sensation that I'm > atop a very tall building looking down at everything. It's very odd to > look down at your own body and still feel that way. I try to shake it off > by putting my hands right in front of my face but it usually doesn't work. > A simple change of scenery, like getting up and walking to the kitchen, > usually dispells the effect. This sometimes happens to me while I'm trying to fall asleep; it can be very un-nerving... It feels like you're not really a part of the world anymore... -Miles
chas@ssc-vax.UUCP (Chas Boyd) (02/21/89)
In article <14825@cup.portal.com>, jxh@cup.portal.com (Jim - Hickstein) writes: > While we're on the subject of human visual perception, specifically > stereopsis, has anyone else noticed that their *perception* of 3-d, > not just stereopsis, occasionally "goes flat" under > stress of, say, sleep deprivation? ... > -Jim Hickstein > jxh@cup.portal.com > ...!sun!portal!cup.portal.com!jxh Rather, I tend to have the opposite problem, I combine flat surfaces to form three-dimensional patterns: repeating patterns on a carpet seem to shift by one or two "periods" and lift up vertically, as though a foot or two of water was in the room. This illusion is destroyed by things like walls, or furniture or people "wading" through the waist-high translucent layer. If you are careful you can even move around in this state, as long as you don't look at walls, furniture, or your feet, or look down a different principle axis of the pattern. (always look in the same direction). Tile floors, or wallpaper work too. (I was stranded overnite in the Charles DeGaule airport when I first noticed) -- UUCP (uw-beaver|fluke)!ssc-vax!ssc-bee!chas (Charles Boyd) ARPA ssc-vax!ssc-bee!chas@uw-beaver WORK (206) 773-3908 HOME (206) 271-7216 <-Warning: a machine usually answers this number...
steve@dcdwest.UUCP (Steve Meloche) (02/22/89)
In article <MY0CeRy00WB6Q9XlRb@andrew.cmu.edu>, po0o+@andrew.cmu.edu (Paul Andrew Olbrich) writes: > This is in reply to Jim Hickstein's earlier comment about losing > stereoscopic effect ... > > Never happened to me, but one thing that does happen to me (and other > people I've talked to) is a wierd sensation that everything's suddenly > shrunk down an order of magnitude, even though it really looks the same. ... > ... It always occurs at night, but I usually am not staying > up extremely late when it happens. Usually I get the sensation that I'm > atop a very tall building looking down at everything. It's very odd to > look down at your own body and still feel that way. ... ... > -- > Drew Olbrich > po0o+@andrew.cmu.edu That is a pretty good description of what I remember happening to me a long time ago (elementary school age). As in the previous article, it only happened at night, when I was laying in bed looking at the far wall of my room. Every- thing there would look somehow smaller and farther away, but it was difficult to quantify my observations. Everything looked the same, but different at the same time. I had always figured that it had to do with young age and immaturity of my nervous system, but up till now I have never heard of anybody else experiencing the same effect. Now, does anybody have an explanation? _____ _____ _____ Steven Meloche | ` | ' ` | ' ITT Defense Communications Division | | | San Diego, CA __|__ | | steve!dcdwest!ucsdhub!... (I think)
malloy@nprdc.arpa (Sean Malloy) (02/23/89)
In article <1232@ssc-bee.ssc-vax.UUCP> chas@ssc-vax.UUCP (Chas Boyd) writes: |In article <14825@cup.portal.com>, jxh@cup.portal.com (Jim - Hickstein) writes: |> While we're on the subject of human visual perception, specifically |> stereopsis, has anyone else noticed that their *perception* of 3-d, |> not just stereopsis, occasionally "goes flat" under |> stress of, say, sleep deprivation? ... |Rather, I tend to have the opposite problem, I combine flat surfaces to form |three-dimensional patterns: repeating patterns on a carpet seem to shift by |one or two "periods" and lift up vertically, as though a foot or two of water |was in the room. I have had effects like this when laying on my back looking up at an acoustic-spray ceilings. The points in the ceiling coating 'drop off' and form a layer of blobs drifting relative to the ceiling. Under some conditions, I can get multiple layers, drifting in different directions. It can be quite entertaining to watch, particularly when listening to music. Sean Malloy Navy Personnel Research & Development Center San Diego, CA 92152-6800 malloy@nprdc.navy.mil
wasg@diomedes.rice.edu (Eric Salituro) (02/23/89)
In article <MY0CeRy00WB6Q9XlRb@andrew.cmu.edu> po0o+@andrew.cmu.edu (Paul Andrew Olbrich) writes: >This is in reply to Jim Hickstein's earlier comment about losing >stereoscopic effect ... > >Never happened to me, but one thing that does happen to me (and other >people I've talked to) is a wierd sensation that everything's suddenly >shrunk down an order of magnitude, even though it really looks the same. Yes, Yes, Yes, Yes! This has happened to me too. Usually, it happens when I'm very tired and relaxed. When I tried to explain the feeling to a friend of mine, she just looked at me funny. (I was really tired and my description was probably not too lucid, either.) I'm a little curious as to what causes this. At least I'm not crazy... This is not a .signature line... Eric Salituro @ Rice University Houston TX 77251-1892 (713) 527-8101 x2474 Life is like a metaphor. INTERNET: wasg@rice.edu
majka@moose.cs.ubc.ca (Marc Majka) (02/23/89)
Paul Andrew Olbrich writes: >Never happened to me, but one thing that does happen to me (and other >people I've talked to) is a wierd sensation that everything's suddenly >shrunk down an order of magnitude, even though it really looks the same. Eric Salituro writes: >This has happened to me too. Usually, it happens when I'm very tired and relaxed. Egad! I thought I was the only one! How common *is* this thing? What is it? I always thought it was the sensation you get when several thousand neurons die simultaneously :-) Followups to sci.med? --- Marc Majka
annie@cs.swarthmore.edu (Annie Fetter) (03/01/89)
In article <1232@ssc-bee.ssc-vax.UUCP> chas@ssc-vax.UUCP (Chas Boyd) writes: > In article <14825@cup.portal.com>, jxh@cup.portal.com (Jim - Hickstein) writes: > > While we're on the subject of human visual perception, specifically > > stereopsis, has anyone else noticed that their *perception* of 3-d, > Rather, I tend to have the opposite problem, I combine flat surfaces to form I have had this happen to me many times, but never with "solid" objects. I often get the 3D depth effect when looking at chain-link fences, nets, and other '2D' repeating patterns of that nature. I can often reach out and put my hand into this 'world' and it's a really disturbing, though nifty, effect. I can't really cite any common factors which have brought this on, except perhaps daydreaming... -annie -- Annie Fetter | annie@cs.swarthmore.edu | VGP-Department of Mathematics | fetter@swarthmr.bitnet | For Office Swarthmore College | ...!rutgers!bpa!swatsun!annie | Use Only Swarthmore, PA 19081 | (215) 328-8225 |
annie@cs.swarthmore.edu (Annie Fetter) (03/01/89)
In article <479@dcdwest.UUCP> steve@dcdwest.UUCP (Steve Meloche) writes: > In article <MY0CeRy00WB6Q9XlRb@andrew.cmu.edu>, po0o+@andrew.cmu.edu (Paul Andrew Olbrich) writes: > > up extremely late when it happens. Usually I get the sensation that I'm > > atop a very tall building looking down at everything. It's very odd to > > look down at your own body and still feel that way. ... > ... > That is a pretty good description of what I remember happening to me a long > time ago (elementary school age). As in the previous article, it only happened > at night, when I was laying in bed looking at the far wall of my room. Every- Gosh, now that I've read a few posting about this, I realize that this happens to me a lot too, at nite, in bed, feeling extremely tired but not being able to fall asleep. I feel like I'm watching a movie of the world around me, and I'm not at all part of it, just an observer. The first time I remember this happening to me was in junior high when I was home sick with the measles, and not a very happy little kid, as you can imagine.But I know that it has happened many times since. Hmmm.. And I thought I was the only one... -annie -- Annie Fetter | annie@cs.swarthmore.edu | VGP-Department of Mathematics | fetter@swarthmr.bitnet | For Office Swarthmore College | ...!rutgers!bpa!swatsun!annie | Use Only Swarthmore, PA 19081 | (215) 328-8225 |
bayes@hpfcdc.HP.COM (Scott Bayes) (03/01/89)
Could this "shrinking" world be a result of a migraine headache, or other
constriction of blood-flow to the brain?
I got two migraines (I'm told so; my head didn't hurt) about 18 mo ago.
The first effect I saw was the world shrinking, much as decribed in this
string, then I got tunnel vision, then finally, I got a "sparkly"
blob shaped patch with a dark middle in the center of my right eye
field of view. All the fun quit after half an hour of lying down. It
hasn't come back since I cut down to 3 cups of coffee a day ("Caffeine,
just say No!").
I've also had a shrinking effect, though more commonly a "distancing"
effect--in which I seem to retreat to the other side of a screen from
the world--when I've had the 'flu and related fever.
Scott "Oh, Wow! Like, look at all the colors! Cool, Man!" Bayes
in Colorful Coloradomcripps@mtuxo.att.com (XMP12-M.CRIPPS) (03/01/89)
In article <MY0CeRy00WB6Q9XlRb@andrew.cmu.edu>, po0o+@andrew.cmu.edu (Paul Andrew Olbrich) writes: (lines deleted) > Usually I get the sensation that I'm > atop a very tall building looking down at everything. It's very odd to > That's very interesting. When I first started wearing glasses (years ago), whenever I took them off, I would feel like I was 2 feet taller. My legs seemed longer, the ground seemed farther away, and my head seemed to be higher off of the ground. I later attributed this to distortions of my peripheral vision caused by the glasses, which my brain would eventually get used to. When I took the glasses off, it would appear distorted to my brain again (i.e., I felt taller). The effect usually "wore off" after a couple of hours (or until I put my glasses on again). It's good to know I'm not the only one.... Mike Cripps mtuxo!mcripps
jkl@csli.STANFORD.EDU (John Kallen) (03/01/89)
In article <4230@mtuxo.att.com> mcripps@mtuxo.att.com (XMP12-M.CRIPPS) groovily writes: >That's very interesting. When I first started wearing glasses (years ago), >whenever I took them off, I would feel like I was 2 feet taller. My legs >seemed longer, the ground seemed farther away, and my head seemed to be >higher off of the ground. When I got my latest pair of glasses (-3 dioptries), wearing them gave me the illusion of being in a "pit" about 40 cm deep. This "pit" would follow me around when walking, causing enormous trouble in staircases. It took a week, for my brain to get accustomed to the fishbowl-like distortion of the objects in my peripheral vision... > >Mike Cripps >mtuxo!mcripps _______________________________________________________________________________ | | | | |\ | | /|\ | John Kallen | |\ \|/ \| * |/ | |/| | | PoBox 11215 "Life. Don't talk to me | |\ /|\ |\ * |\ | | | | Stanford CA 94309 about life." _|_|___|___|____|_\|___|__|__|_jkl@csli.stanford.edu___________________________
peter@ficc.uu.net (Peter da Silva) (03/01/89)
In article <2492@masada.cs.swarthmore.edu>, annie@cs.swarthmore.edu (Annie Fetter) writes: > I have had this happen to me many times, but never with "solid" objects. I > often get the 3D depth effect when looking at chain-link fences, nets,... I do this, too. Sometimes when I'm bored I'll play games with a regular pattern like that (fences, tiled floors, bricks) adjusting the perceived distance to the pattern and so on... Just another data point, folks. -- Peter da Silva, Xenix Support, Ferranti International Controls Corporation. Work: uunet.uu.net!ficc!peter, peter@ficc.uu.net, +1 713 274 5180. `-_-' Home: bigtex!texbell!sugar!peter, peter@sugar.uu.net. 'U` People have opinions. Companies have policy. And typos are my own business.
jwi@lzfme.att.com (Jim Winer @ AT&T, Middletown, NJ) (03/01/89)
> In article <MY0CeRy00WB6Q9XlRb@andrew.cmu.edu>, po0o+@andrew.cmu.edu (Paul Andrew Olbrich) writes: > (lines deleted) > > Usually I get the sensation that I'm > > atop a very tall building looking down at everything. It's very odd to > > This whole general phenomena(sp?) seems 1) natural, 2) common (me too), and 3) to be generally misinterpreted by some as an _out of body_ experience. If you changed the subject to _out of body experiences_ I think you'd get a lot more responses, but the only net conclusions would be that a) it's a pretty common experience, and b) it probably represents an altered state of consciousness. Jim Winer ..!lzfme!jwi I believe in absolute freedom of the press. I believe that freedom of the press is the only protection we have from the abuses of power of the church, from the abuses of power of the state, from the abuses of power of the corporate body, and from the abuses of power of the press itself. Those persons who advocate censorship offend my religion.
pfarrell@anselm.UUCP (Gladiator) (03/02/89)
Here is an interesting thought. If there were no shadows everything would look completely flat. Anybody agree or disagree with that statement? -- Patrick Farrell @ St. Anselm's college, Goffstown N.H. 1-603-472-2378 dartvax!anselm!pfarrell "Laugh and the world ignores you. Crying doesn't help either."
aubrey@val.UUCP (Aubrey McIntosh) (03/02/89)
In article <2492@masada.cs.swarthmore.edu> annie@cs.swarthmore.edu (Annie Fetter) writes: >I have had this happen to me many times, but never with "solid" objects. I >often get the 3D depth effect when looking at chain-link fences, nets, and >other '2D' repeating patterns of that nature. I can often reach out and put >my hand into this 'world' and it's a really disturbing, though nifty, effect. > >I can't really cite any common factors which have brought this on, except >perhaps daydreaming... > I've been interested in stereo vision since I had a stereo vision viewer as a child, and often I have taken 'stereo' photographs by moving a foot or so and snapping a second photograph. I've learned to view the 3-D molecular drawings in journals, such as the Journal of Inorganic Chemistry, very fluently. What I have noticed happening is that, while in a photographic darkroom, when I first turn on the lights and there is an absence of orientation and visual cues, I 'lock on' to the stippling patterns on the wall incorrectly, and I have a feeling of vertigo and of being cross-eyed. This incorrect orientation usually is difficult to resolve, and almost always requires touching the wall and then focusing on the tip of my finger. oakhill!val!aubrey%cs.utexas.edu -- -------------------------------------------------------------- a Modula-2 house... 1-(512)-346-5781 (v) Austin, TX 78759 ...!cs.utexas.edu!oakhill!val!aubrey
thecloud@dhw68k.cts.com (Ken McLeod) (03/02/89)
In article <4230@mtuxo.att.com> mcripps@mtuxo.att.com (XMP12-M.CRIPPS) writes: >In article <MY0CeRy00WB6Q9XlRb@andrew.cmu.edu>, po0o+@andrew.cmu.edu (Paul Andrew Olbrich) writes: > (lines deleted) >> Usually I get the sensation that I'm >> atop a very tall building looking down at everything. It's very odd to >> > [various experiences with ceilings, eyeglasses, etc. deleted] Time for me to add my 2 cents to the pot: I can vividly recall several times when I was lying in bed sick, usually in a dimly-lit room, staring up at a white spray-on acoustic ceiling. No pattern recognition or 3-D layers, though; rather, I would get the sensation that the area of the ceiling was infinitely vast, and that I would somehow have to hold it up or it would come down and crush me like a bug. :-( Depth perception was definitely altered, and the far corner of the room seemed infinitely far away from me. I always attributed this to drugs, though. :-) -k -- ========== ....... ============================================= Ken McLeod :. .: felix!dhw68k!thecloud@ics.uci.edu ========== :::.. ..::: InterNet: thecloud@dhw68k.cts.com //// =============================================
foo@titan.rice.edu (Mark Hall) (03/02/89)
In article <238@anselm.UUCP> pfarrell@anselm.UUCP (Gladiator) writes: >Here is an interesting thought. If there were no shadows everything >would look completely flat. Anybody agree or disagree with >that statement? Disagree. It is very easy to produce computer-generated pictures with no shadows. A sphere does not look like a circle ( assuming that you have any non-ambient light.) no shadows (Not =) no lighting effects You can have highlights without having shadows. Some EEs here are working on a computer vision system that uses lighting (highlights) and multiple controllable light sources to try and determine shape. Shadows are a hinderance for them. - mark
po0o+@andrew.cmu.edu (Paul Andrew Olbrich) (03/03/89)
Patrick Farrell writes: > Here is an interesting thought. If there were no shadows everything > would look completely flat. Anybody agree or disagree with > that statement? Better yet, wouldn't everything look wierd if we didn't get gray shade input? (That is, only information like "this is red," and "this is greenish-blue.") ... And everything was the same level of brightness. No shadows here, and walking through unlit rooms would be easy. Everything would have pretty much of a fake appearance. (Yessir, I'm a wierd one ...) Peter da Silva writes: > I do this, too. Sometimes when I'm bored I'll play games with a regular > pattern like that (fences, tiled floors, bricks) adjusting the perceived > distance to the pattern and so on... I do this with telephone cords occasionally. You just cross your eyes a little and make it appear closer to you. Then you try to reach out and touch it and miss. Works well with most wallpaper, too. Somebody should print up some red-blue wallpaper that's fun to look at when you're wearing 3D glasses ... -- Drew Olbrich po0o+@andrew.cmu.edu "Because cows have a complex four-stomach digestive system, they are technically incapable of vomiting as we know it."
bob@reed.UUCP (Mythical Bob Ankeney) (03/03/89)
In article <238@anselm.UUCP> pfarrell@anselm.UUCP (Gladiator) writes: > > > > >Here is an interesting thought. If there were no shadows everything >would look completely flat. Anybody agree or disagree with >that statement? >-- I would have to disagree. There are a number of factors in depth perception. Eye convergence is probably the strongest, for objects that are relatively close. Other depth cues are available for objects farther away (mostly learned, like known objects in front of other objects). I would agree that shadows are very important. Ever notice how flat things look at noon with the sun straight overhead as opposed to when shadows are being cast? (I really notice this looking at a forest). Bob Ankeney bob@reed.BITNET -- --------------------------------------------------------------------------- "You can't argue with a sick mind." Bob Ankeney ...!tektronix!reed!bob or bob@reed.BITNET
jxh@cup.portal.com (Jim - Hickstein) (03/03/89)
...yes, but all this about stippling patterns and chain-link fences is not at all what I meant when I started this. Those are merely illusions arising out of the inherent limitations of accomodation as a stereo cue. I'm talking about the loss of *perception*, not just a single cue or the failure of a single cue to give correct results. Of all the talk about patterned surfaces, I've only seen one response (I think) that indicates the experience I'm talking about. In this mode, I really couldn't say whether I could touch that wall over there or not until I put my arm out and it works (or doesn't). This is the same FOR THE MOON (world knowledge notwithstanding). All cues are ignored, except at the very highest levels of cognition (no, I probably can't touch the moon); but this is a phenomenon (singular) of the visual cortex (um, I think). Any others? Really? -jxh
Michael_J_Ward@cup.portal.com (03/03/89)
With all of the discussion of 3-D perception on the net lately, I wonder how many people see the effect I notice when looking at complex images of solid primary color patterns, wherein one color is apparently floating above another? I have always assumed it was due to bad eyesight (though it is still there when fully corrected), astigmatism (ditto) or color-sensitivity variations (one eye sees things somewhat more reddish than the other, and always has). It seems likely to me that the brain is interpreting some visual clue from the color differentiation to mean that the colors are at different distances. It is also true that the different colors will focus at different distances in the back of the eye, but I never thought that difference was large enough to cause this effect.
consult@osiris.UUCP (Unix Consultation Mailbox ) (03/04/89)
In article <3241@ficc.uu.net> peter@ficc.uu.net (Peter da Silva) writes: >In article <2492@masada.cs.swarthmore.edu>, annie@cs.swarthmore.edu (Annie Fetter) writes: >> I have had this happen to me many times, but never with "solid" objects. I >> often get the 3D depth effect when looking at chain-link fences, nets,... > >I do this, too. Sometimes when I'm bored I'll play games with a regular >pattern like that (fences, tiled floors, bricks) adjusting the perceived >distance to the pattern and so on... Yeah, pretty much any surface with a regular pattern that has a small size (relative to your viewpoint) - the smaller the size of the pattern, the more intense the effect seems to be (to me anyway). You can do it with a keyboard too, it makes the keycap legends look like they're in some alien alphabet. I like to try realigning the pattern as I stare at it, to find out how close or distant I can make it appear without making my eyes sore. My favorites are tiled bathroom floors and the pierced sheetmetal panels they make radiator covers with. I must spend a lot of time looking at them. :-) phil
eugene@eos.UUCP (Eugene Miya) (03/04/89)
Purchase the 35 mm slide set on Optical Illusions from the Exploratorium.
One interesting consequence I learned in grad school was to rotate images
of lunar craters and mountains upside down. Mountains appear to become
craters and craters become mountains without adequate cues.
Another gross generalization from
--eugene miya, NASA Ames Research Center, eugene@aurora.arc.nasa.gov
resident cynic at the Rock of Ages Home for Retired Hackers:
"Mailers?! HA!", "If my mail does not reach you, please accept my apology."
{uunet,hplabs,ncar,decwrl,allegra,tektronix}!ames!aurora!eugene
"Post follow ups. Contribute to network noise."carroll@s.cs.uiuc.edu (03/05/89)
RE: 3-D from repeating 2-D patterns
I first noticed this staring up at the roof of a dodge van, with a regular
patterns of holes in it. I've since learned how to do it on demand, even
on a keyboard (so it looks like the keys have ``stretched'' up toward me).
Look straight down at the G H keys, and let your eyes go unfocused and
somewhat crossed. Try to get the image of the G on the right to overlap
the H on the left, and then (slowly) try to focus in on this 'GH' key.
Don't try to see what letter is on it clearly - this forces your brain to
make a choice, and destroys the perception. The same technique works (for me)
on any repeating pattern, by letting the images slide onto one another.
P.S. I haven't experienced asteriopsis or the distance effect, though.
Alan M. Carroll "And then you say,
carroll@s.cs.uiuc.edu We have the Moon, so now the Stars..." - YES
CS Grad / U of Ill @ Urbana ...{ucbvax,pur-ee,convex}!s.cs.uiuc.edu!carrollClassic_-_Concepts@cup.portal.com (03/05/89)
> If there were no shadows everything would look flat. Anyone agree or > disagree with me? I disagree. I can think of a number of other visual cues that we use to measure volume and distance, for example: 1. Color changes with distance and around edges. I mean colors other than shadows. Like looking at the horizon and seeing things darker there. 2. You would still get 'perspective' as you looked at objects, due to narrowing in the distance (like a road), or smaller, like a person standing at a distance compared to one standing close by. 3. Fuzzy versus sharp. Our vision allows us to focus more clearly on closer objects (except of course, in cases of people requiring corrective lenses for their eyes) and objects in the distance fuzz out gradually. There may be others, but just off the cuff, without thinking about it for more than a few seconds, those are ones that come to mind. -LH Wait a moment, I just thought of some others. If there were no shadows, we might rely more on other senses, like smell and hearing. They also provide distance cues, e.g., you're standing in front of a school bus, the amount of diesel smell might provide cues as to the length of the bus, or the volume of engine noise could contribute to our 'perception' of how flat it appears. So without shadows, things might appear flat at first, but I wouldn't be surprised if we adapted rather quickly and relied on other sources of info.
lfoard@wpi.wpi.edu (Lawrence C Foard) (03/06/89)
It is interesting how many ways there are of fooling the human visual system!
This brings up a problem with artificial vision, if you look at something that
doesn't make complete sence to you brain by itself (strange wallpaper etc) you
can still recognize it by comparing it with other things you have seeing, once
you associate it with something familiar you now see what it is (or atleast
what you think it is). The problem this brings up for artificial vision is
that even with very good visual abilitys we are unable to form a unique 3D
model of an object when it is not clearly visible, instead we guess what it is
and check if it matchs something we have seen before. Has this method ever been
used for artificial vision?
--
Disclaimer: My school does not share my views about FORTRAN.
FORTRAN does not share my views about my school.rrw@naucse.UUCP (Robert Wier) (03/06/89)
The technique of fusing two images into a stereoscopic image while not converging your eyes can lead to an amusing capability. I first learned this technique when I became interested in stereo photography, and got to where I could look at the old stere-optican cards without using a viewer. I discovered that the same thing could frequently be done with the puzzles that sometimes appear in newspapers wherein a cartoon is repeated two times, and the reader is to find 6 (small) differences in the drawings (or 5, or 7, ... whatever). It seems that the cartoons are usually an exact match in places where the differences have not been intentionally introduced (I assume one original drawing is made, and then some changes are introduced to arrive at the second one). By fusing the two drawings together, the areas of difference literally leap out of the page at you. I have a number of times used this technique and amazed people by circling all the differences in the cartoons within 10 seconds, while everyone else took several minutes. Give it a try the next time you see one of these puzzles. - Bob Wier College of Engineering Flagstaff, Arizona Northern Arizona University ...arizona!naucse!rrw | BITNET: WIER@NAUVAX | *usual disclaimers*
grady@fxgrp.UUCP (Steven Grady) (03/07/89)
In article <1188@naucse.UUCP> rrw@naucse.UUCP (Robert Wier) writes: > > > It seems that the cartoons > are usually an exact match in places where the differences have > not been intentionally introduced (I assume one original drawing > is made, and then some changes are introduced to arrive at the second > one). By fusing the two drawings together, the areas of difference > literally leap out of the page at you. I have a number of times > used this technique and amazed people by circling all the differences > in the cartoons within 10 seconds, while everyone else took several > minutes. Yeah, I do that too. It seems kind of like cheating to me, though. BUt the real problem is that papaer they used to be in (aren't there anymore) had one picture above the other. So I would always look rather gooky staring at the picture sideways... Steven ...!ucbvax!grady grady@postgres.berkeley.edu "Nice tie... BONEHEAD!"
randy@gtx.com (Randy D. Miller) (03/07/89)
rrw@naucse.UUCP (Robert Wier) writes: > The technique of fusing two images into a stereoscopic > image while not converging your eyes can lead to an amusing > capability. I first learned this technique when I became > interested in stereo photography, and got to where I could look > at the old stere-optican cards without using a viewer. I discovered > that the same thing could frequently be done with the puzzles that > sometimes appear in newspapers wherein a cartoon is repeated two > times, and the reader is to find 6 (small) differences in the > drawings (or 5, or 7, ... whatever). It seems that the cartoons I've amused myself for countless hours experimenting with this "merging of two images". Like another poster, I've also found that I could take stereo photographs with my 35mm camera, just by offsetting the shots by a few inches. The exact offset doesn't matter; your brain will make the merged image appear to have the correct depth effect. My vacation photo album now contains stereo shots. Friends and relatives can't figure why I put two pictures that look alike into the album (:-). Similar to the "find-the-differences" newspaper cartoon, I've found that I can lay two 8.5 x 11 inch printed pages side by side and merge the two images so that I can spot any typographical differences. You can become a human "diff". Sometimes you can merge the images of two chairs sitting side by side, or two faces that are similar in size and shape, or two coins laying side by side, or two anything. Makes sitting in a waiting room more interesting. -- Randy D. Miller ...!sun!sunburn!gtx!randy (602) 870-1696 GTX Corp., 8836 N. 23rd Avenue, Phoenix, Arizona 85021
jeff@censor.UUCP (Jeff Hunter) (03/07/89)
In article <UY3KcRy00XokQ1AlcS@andrew.cmu.edu>, po0o+@andrew.cmu.edu (Paul Andrew Olbrich) writes: > Patrick Farrell writes: > > Here is an interesting thought. If there were no shadows everything > > would look completely flat. Anybody agree or disagree with > > that statement? > Better yet, wouldn't everything look wierd if we didn't get gray shade input? > (That is, only information like "this is red," and "this is greenish-blue.") > And everything was the same level of brightness. No shadows here, and walking > through unlit rooms would be easy. Everything would have pretty much of a fake > appearance. (Yessir, I'm a wierd one ...) > Have you ever seen those op-art pictures where there is bright blue lettering on a red background and the edges flicker badly enough to make your head ache? A recent Sci. Am. said the effect is due to the split in the brain between the black-and-white vision system, and the colour one. The B&W is used to pick out the edges of the scene, and the other picks out blobs of colour in somewhat less detail. The two visions are combined in somewhat the same manner as a colouring book. The trouble comes when two colours are picked that reflect almost exactly the same amount of light. The B&W system just sees a uniform grey. The colour system spots an edge (between the two colours) and asks the B&W to find it.... Your eyes and brain continue to oscillate until you look away. I'll agree that walking thru unlit rooms would be easy, but keep your eyes shut tight in the sunshine! :-) > "Because cows have a complex four-stomach digestive system, they are technically > incapable of vomiting as we know it." ... and if they have "gassid indigestion" they can die from it. A pretty high price for the ability to eat lawns.... -- ___ __ __ {utzoo,lsuc}!censor!jeff (416-595-2705) / / /) / ) -- my opinions -- -/ _ -/- /- The first cup of coffee recapitulates phylogeny... (__/ (/_/ _/_ Barry Workman
u-jmolse%sunset.utah.edu@wasatch.UUCP (John M. Olsen) (03/08/89)
In article <207400002@s.cs.uiuc.edu> carroll@s.cs.uiuc.edu writes: >RE: 3-D from repeating 2-D patterns >I first noticed this staring up at the roof of a dodge van, with a regular >patterns of holes in it. I've since learned how to do it on demand, even >on a keyboard (so it looks like the keys have ``stretched'' up toward me). >Look straight down at the G H keys, and let your eyes go unfocused and >somewhat crossed. >Alan M. Carroll "And then you say, >carroll@s.cs.uiuc.edu We have the Moon, so now the Stars..." - YES >CS Grad / U of Ill @ Urbana ...{ucbvax,pur-ee,convex}!s.cs.uiuc.edu!carroll Okay, all you cross-eyed folks. Read this: 12345678901245q678912l45q78t912l45q7t9z12l457t*9z12l45t*9z1T2l45t*9z1Tl45t*$9 qwertyui5nqwrtayui5qwxrtayui5qwxrayui5qwxzrauiC5qwxzraiCt5qwxzaiCt57qwza>iCt5 asdfghjkl;asfghjkl;aszfghklr;aszfghkr;yaszfgkr;yaszgfgr;ya.szggrT;ya.sggrT);y zxcvbnm,./zxvb1nm,.zxyvb1m,>.zxyvb1m>.-zxyvbm>T.-xyPvb>TG.-xyPb>pTG.-xPbT>pTG 12345678901245r678912745r78B912745r7B9t127457By9t27Y45By9t2N7Y5Bry9t2NY5Bry*9 ^ ^ This is the repeat frequency. (Sorry for the ugly font.) Cross-eyed, the text is recessed. Going diverged makes the text poke out. This technique *might* show up in a not-too-distant future Scientific American if Mr. Dewdney things there are enough bug-eyed readers. :^) Imagine having stereoscopic wallpaper where only you can see what's there. The answer: ( quit now if you want to figure it out yourself :^) Hi thErE. /\/\ /| | /||| /\| | John M. Olsen, 1547 Jamestown Drive /\/\ \/\/ \|()|\|\_ |||.\/|/)@|\_ | Salt Lake City, UT 84121-2051 \/\/ /\/\ | u-jmolse%ug@cs.utah.edu or ...!utah-cs!utah-ug!u-jmolse /\/\ \/\/ "A full mailbox is a happy mailbox" \/\/
eugene@eos.UUCP (Eugene Miya) (03/08/89)
In article <902@gtx.com> randy@gtx.UUCP (Randy D. Miller) writes: >rrw@naucse.UUCP (Robert Wier) writes: >> The technique of fusing two images into a stereoscopic >> image > >I've amused myself for countless hours experimenting with this "merging >of two images". Like another poster, I've also found that I could take >stereo photographs with my 35mm camera, just by offsetting the shots by > >Similar to the "find-the-differences" newspaper cartoon, I've found >that I can lay two 8.5 x 11 inch printed pages side by side and merge >the two images so that I can spot any typographical differences. You >can become a human "diff". Have you considered taking the job of an astronomical blink comparator? ;-) [for those not familiar, the comparator is a piece of equipment, not a person]. I am thinking (low level) about buying a stereo camera. Several are available as well as viewers. I suggest if you are really interested in stereo pairs, the book by Wanless published by Hubbard (with the cheap stereo glasses) on aerial photographs. You can feel like a bomber pilot. 8-) As mentioned in a criticism on scientific visualization, I think the best current work is being done by the biologists who's complexity problems just grab an issue of science and keep your stereo glasses handy. You can continue to take crude stereo, but if you get a collection of slightly inconsistent base pairs, handling becomes a pain. P.S. I just retrieved my books (about a dozen) on image processing for remote sensing: Bernstein, Simonett and Lintz, Wolf, Castleman, Sabins, Swain, etc. Another gross generalization from --eugene miya, NASA Ames Research Center, eugene@aurora.arc.nasa.gov resident cynic at the Rock of Ages Home for Retired Hackers: "Mailers?! HA!", "If my mail does not reach you, please accept my apology." {uunet,hplabs,ncar,decwrl,allegra,tektronix}!ames!aurora!eugene "Post follow ups. Contribute to network noise."
bayes@hpfcdc.HP.COM (Scott Bayes) (03/09/89)
>Okay, all you cross-eyed folks. Read this: > >12345678901245q678912l45q78t912l45q7t9z12l457t*9z12l45t*9z1T2l45t*9z1Tl45t*$9 >qwertyui5nqwrtayui5qwxrtayui5qwxrayui5qwxzrauiC5qwxzraiCt5qwxzaiCt57qwza>iCt5 >asdfghjkl;asfghjkl;aszfghklr;aszfghkr;yaszfgkr;yaszgfgr;ya.szggrT;ya.sggrT);y >zxcvbnm,./zxvb1nm,.zxyvb1m,>.zxyvb1m>.-zxyvbm>T.-xyPvb>TG.-xyPb>pTG.-xPbT>pTG >12345678901245r678912745r78B912745r7B9t127457By9t27Y45By9t2N7Y5Bry9t2NY5Bry*9 >^ ^ >This is the repeat frequency. (Sorry for the ugly font.) > >Cross-eyed, the text is recessed. Going diverged makes the text poke out. >This technique *might* show up in a not-too-distant future Scientific >American if Mr. Dewdney things there are enough bug-eyed readers. :^) >Imagine having stereoscopic wallpaper where only you can see what's there. > >The answer: ( quit now if you want to figure it out yourself :^) > >Hi thErE. > >/\/\ /| | /||| /\| | John M. Olsen, 1547 Jamestown Drive /\/\ >\/\/ \|()|\|\_ |||.\/|/)@|\_ | Salt Lake City, UT 84121-2051 \/\/ >/\/\ | u-jmolse%ug@cs.utah.edu or ...!utah-cs!utah-ug!u-jmolse /\/\ >\/\/ "A full mailbox is a happy mailbox" \/\/ Very nice! Diverged is easy for me. I do it all the time (human "diff", and stereo pair merge). Cross-eyed is very difficult. I can't convince my eyes to focus. I was able to hold cross-eyed long enough to see the "H" and the adjacent "i", but not to actually read. Reading diverged is natural. The proximity of the "y" and "u" in the "5qwxrtayui" background is a problem. When looking at the "i", the "y" and "u" between the body and the dot of the "i" tend to merge (because of their similarity of shape on my CRT), and come to the foreground, somewhat bashing the "i" (and the eye :-) Do you have a "banner" program that'll lay down the text on the background? If so, and if you have no problems with mailing me a copy, please do so. I'd never thought of trying that effect. It's neat! You might also consider Jearle Walker (SciAm--Amateur Scientist). He occasionally seems to do perception articles. | Scott Bayes | Scott Bayes| | Scott Bayes | Scott Bayes |
jdchrist@watcgl.waterloo.edu (Dan Christensen) (03/09/89)
In article <1247@wasatch.UUCP> u-jmolse%sunset.utah.edu.UUCP@wasatch.UUCP (John M. Olsen) writes: >Okay, all you cross-eyed folks. Read this: > >12345678901245q678912l45q78t912l45q7t9z12l457t*9z12l45t*9z1T2l45t*9z1Tl45t*$9 >qwertyui5nqwrtayui5qwxrtayui5qwxrayui5qwxzrauiC5qwxzraiCt5qwxzaiCt57qwza>iCt5 >asdfghjkl;asfghjkl;aszfghklr;aszfghkr;yaszfgkr;yaszgfgr;ya.szggrT;ya.sggrT);y >zxcvbnm,./zxvb1nm,.zxyvb1m,>.zxyvb1m>.-zxyvbm>T.-xyPvb>TG.-xyPb>pTG.-xPbT>pTG >12345678901245r678912745r78B912745r7B9t127457By9t27Y45By9t2N7Y5Bry9t2NY5Bry*9 > >Cross-eyed, the text is recessed. Going diverged makes the text poke out. I can't make my eyes do this, but shouldn't the text poke out when you cross your eyes and be recessed when you diverge your eyes? ---- Dan Christensen, Computer Graphics Lab, jdchrist@watcgl.uwaterloo.ca University of Waterloo, Waterloo, Ont. jdchrist@watcgl.waterloo.edu
u-jmolse%sunset.utah.edu@wasatch.UUCP (John M. Olsen) (03/09/89)
In article <8499@watcgl.waterloo.edu> jdchrist@watcgl.waterloo.edu (Dan Christensen) writes: >u-jmolse%sunset.utah.edu.UUCP@wasatch.UUCP (John M. Olsen) writes: >>Okay, all you cross-eyed folks. Read this: >>[funky random looking text] >>Cross-eyed, the text is recessed. Going diverged makes the text poke out. >I can't make my eyes do this, but shouldn't the text poke out when you >cross your eyes and be recessed when you diverge your eyes? >Dan Christensen, Computer Graphics Lab, jdchrist@watcgl.uwaterloo.ca >University of Waterloo, Waterloo, Ont. jdchrist@watcgl.waterloo.edu I was speaking about the "secret message" with reference to the background random text. There will be two apparent depths in the image, and I was completely ignoring the fact that the whole thing would appear closer or farther with respect to the screen it's shown on. If you examine the data closely, you will find that each letter is one of two offsets from it's previous or following ocurrence. /\/\ /| | /||| /\| | John M. Olsen, 1547 Jamestown Drive /\/\ \/\/ \|()|\|\_ |||.\/|/)@|\_ | Salt Lake City, UT 84121-2051 \/\/ /\/\ | u-jmolse%ug@cs.utah.edu or ...!utah-cs!utah-ug!u-jmolse /\/\ \/\/ "A full mailbox is a happy mailbox" \/\/
klg@dukeac.UUCP (Kim Greer) (03/09/89)
In article <1247@wasatch.UUCP> u-jmolse%sunset.utah.edu.UUCP@wasatch.UUCP (John M. Olsen) writes: +In article <207400002@s.cs.uiuc.edu> carroll@s.cs.uiuc.edu writes: ++RE: 3-D from repeating 2-D patterns + +Okay, all you cross-eyed folks. Read this: + +12345678901245q678912l45q78t912l45q7t9z12l457t*9z12l45t*9z1T2l45t*9z1Tl45t*$9 +qwertyui5nqwrtayui5qwxrtayui5qwxrayui5qwxzrauiC5qwxzraiCt5qwxzaiCt57qwza>iCt5 +asdfghjkl;asfghjkl;aszfghklr;aszfghkr;yaszfgkr;yaszgfgr;ya.szggrT;ya.sggrT);y +zxcvbnm,./zxvb1nm,.zxyvb1m,>.zxyvb1m>.-zxyvbm>T.-xyPvb>TG.-xyPb>pTG.-xPbT>pTG +12345678901245r678912745r78B912745r7B9t127457By9t27Y45By9t2N7Y5Bry9t2NY5Bry*9 +^ ^ +This is the repeat frequency. (Sorry for the ugly font.) + +Cross-eyed, the text is recessed. Going diverged makes the text poke out. +This technique *might* show up in a not-too-distant future Scientific +American if Mr. Dewdney things there are enough bug-eyed readers. :^) +Imagine having stereoscopic wallpaper where only you can see what's there. + +The answer: ( quit now if you want to figure it out yourself :^) + +Hi thErE. + +/\/\ /| | /||| /\| | John M. Olsen, 1547 Jamestown Drive /\/\ +\/\/ \|()|\|\_ |||.\/|/)@|\_ | Salt Lake City, UT 84121-2051 \/\/ +/\/\ | u-jmolse%ug@cs.utah.edu or ...!utah-cs!utah-ug!u-jmolse /\/\ +\/\/ "A full mailbox is a happy mailbox" \/\/ 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
u-jmolse%sunset.utah.edu@wasatch.UUCP (John M. Olsen) (03/10/89)
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. /\/\ /| | /||| /\| | John M. Olsen, 1547 Jamestown Drive /\/\ \/\/ \|()|\|\_ |||.\/|/)@|\_ | Salt Lake City, UT 84121-2051 \/\/ /\/\ | u-jmolse%ug@cs.utah.edu or ...!utah-cs!utah-ug!u-jmolse /\/\ \/\/ "A full mailbox is a happy mailbox" \/\/