Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!bbn!bbn.com!cosell
From: cosell@bbn.com (Bernie Cosell)
Newsgroups: comp.graphics
Subject: Re: 3-D perceptual abilities
Keywords: TV 3-D graphic
Message-ID: <35258@bbn.COM>
Date: 29 Jan 89 17:35:58 GMT
References: <6382@thorin.cs.unc.edu> <25652@sgi.SGI.COM> <985@wasatch.UUCP>
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Reply-To: cosell@BBN.COM (Bernie Cosell)
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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
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