Re: [tech-3d] Re: Terms and Definitions

[Bruce Springsteen <bsspringsteen@xxxxxxxxx>]

Abram, probably slightly mortified, implored:

> Will Ray, Bruce and Gabriel
> please stop discussing me and stick to 3D subjects ? :-)

Gladly.  It's sometimes difficult to address the message without assessing
the messenger.  Personalities intrude despite our best attempts at cold
reason.  Even on Tech3D. ;-)

> John Toeppen:
> >(...) a cheap trick to encourage membership

And Abram mentioned the ongoing debate on whether to let the glossary
circulate without charge among non-ISU folks.  It would seem a choice must
be made either to spread new information freely among the 3D community, by
all available avenues and without regard to affiliation, or to treat such
work as each organization's precious asset to be rationed on a quid pro
quo basis (You want to know what we think?  Join our club.  Or pay us for
it.)  Clearly you can't do both at once, but each position has strong
advocates, so ISU is trying a "compromise" where the two goals are pursued
in turn.  Chuck's skeptical satire is more understandable in light of that
state of affairs.  Will John Rupkalvis be apprehended by the ISU police
for appropriating their glossary as the starting point for the SMPTE's
project?  Can ISU members on T3D promote their nomenclature while it is
officially private property?  How can you sell people on the virtues of
the glossary, and thereby attract them to ISU, without showing it to them?
 A leap of faith?  I think ISU has enough intrinsic appeal for new members
without holding the glossary hostage at its own expense.

Anyway, at the risk of giving away the store and landing in manacles and
muzzle, I have to clarify my earlier comment, and note that "stereo
magnification" does not appear as a separate term in the glossary, but is
only used in passing in the definition for "tautomorphic image." 
"Orthostereoscopic image" is left a bit vague, demanding only that an
image appear "correctly spaced as in the original view," which leaves
plenty of room for individual interpretation.

About a year ago, I half-jokingly proposed a redefinition of
"orthostereoscopy" to refer only to the condition of *viewing*
stereographs so that each eye sees its corresponding image in the proper
orientation and angle of view, duplicating the two taking perspectives and
*without* regard to stereo base or the interpupillary of some hypothetical
viewing person.  I've since come to love that proposal as only a doting
father would, and wish it could be immortalized thus: "Orthostereoscopic
viewing" is perspectively correct but does not refer to any fixed scale of
subject to observer while in "tautomorphic stereoscopy" stereo scenes are
made and viewed to duplicate a given "real" scene in perspective, subject
size and observer IPD.  Tautomorphic stereo thus becomes a special case of
orthostereo - in fact taking over ortho's popular meaning of seeing
"exactly as in life."  This leaves orthostereo free to be both broader and
more precise.  It also distinguishes *purposeful* scaling choices in
making stereographs (stereo magnification) from *inadvertent* distortions
of perspective in viewing them.

The ISU glossary sort of implies such a distinction, without actually
making it.

Now I'm curious - how does accommodation figure into any of the competing
definitions of "ortho?"  John Toeppen mentioned it as a factor in
orthostereo and I let it pass, but it sounds like he might require more
than even my "tautomorphic" condition would.  Can any stereoviewing scheme
duplicate the variations in accommodation that occur in real space vision?
 I'm not sure how.  If so, we seem to be raising the bar on stereo
"reality" in a way that could throw our nomenclature into a real tizzy!

Bruce

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