Path: utzoo!utgpu!water!watmath!clyde!ima!bbn!cosell.bbn.com!cosell
From: cosell@cosell.bbn.com (Bernie Cosell)
Newsgroups: comp.graphics
Subject: Re: Re: Interactive Stereo Viewing
Message-ID: <20092@bbn.COM>
Date: 21 Jan 88 21:16:39 GMT
References: <146@rocky8.rockefeller.edu> <4570004@hpiacla.HP.COM>
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Reply-To: cosell@bbn.com.UUCP (Bernie Cosell)
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I think that the current formulations (and transform matrices, etc) for
generating stereo pairs have it a bit wrong.  You should **NOT**
converge the two views you generate -- they should be from offset
perspective origins to be sure, but the two primary sight axes should
be _parallel_.  There is a LOT of info about this in the world of
stereo photography, where they have done lots of experiments in the
last 90 or so years.

From "The world of 3D, a practical guide to stereo photography" by
J G Ferwerda:
   Those without much experience with stereo often think that the lens
   axes while shooting the left and right image, should be trained somewhat
   `towards each other'.  For instance, while shooting a flowering shrub
   at a distance of 3 m, it seems obvious that in both cases a certain
   flower should be kept in the centre of the viewfinder for each shot.
   However, this is not the case.  Even if the subject that is to be taken
   is very near -- especially then -- the lens axes should not be
   trained `towards each other'.

A later chapter in the book discusses the sorts of distortions taht
arise if you DO converge the axes.
   __
  /  )                              Bernie Cosell
 /--<  _  __  __   o _              BBN Labs, Cambridge, MA 02238
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