NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/sci/virtual/3760

Internet Message Format | 1992-11-20 | 9.4 KB

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From: [e-mail] (John Costella)
Newsgroups: sci.virtual-worlds
Subject: Re: PHIL: VR and VISUAL FORMS (reply to John Costella)
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Date: 20 Nov 92 05:30:22 GMT
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Disclaimer: the following post is a little long; brain death upon ploughing
through it is your responsibility. :) I have, however, tried not to "quote"
excessive bits of previous posts, though.

> Let me first thank John Costella for reading, and interpreting for

No problems, Tom.

> all of the technical postings, etc., which are very difficult going for me.
> An example may be the Gallilean Anti-Aliasing posting which is still
> challenging me.

<whack> Yes, I got that back-hander. <grin> We must look like Laurel and
Hardy trying to understand each other. <larger grin>

> >    represented a unified field of dimensional values because space, time,
> >    and body are incorporated into a single expression of rate.
> >
> > This sounds like gobbledegook to a physicist. At least for the scientific
>
> I would like to point out for the physicists who begin to feel quite smug at
> this point that within the mathematical heritage of ancient Greece Euclid
> suddenly created these distinct categories of space, time, and body

Ah, OK, I'm getting the (general) drift. The term `rate' may be one that is
another scientist-misleader. I take this one back, pending seeing the full
paper.

> > General relativity
> > ------------------
> >    I will use theories of general relativity, first touched on during
> >    discussions of Cubist temporal notations, to illustrate some
> >
> > A physicist must be allowed to barf upon reaching these paragraphs. One
> > might conceivably imagine that the term "general relativity" has an
> > artistic meaning completely distinct from its physics meaning; however,
> > mention of "inertial frames" and "local effects" makes this impossible.
>
> Please feel free to barf, I am not offended at my naivet, and I hope you
> aren't either; these efforts at communication across disciplinary boundaries
> are sometimes very gut-wrenching.

OK. <barf>. Sorry about that. It's just that GR is about the *only*
physical theory that really seems to be A-OK, and we don't like it
thrown around recklessly. (Non-Euclidean) geometry is a term I'd be
happy with.

> >    The general laws of nature are to be expressed by equations which
> >    hold good for all systems of coordinates, that is, are generally
> >    covariant with respect to any substitutions whatever (generally
>
> This covariance is precisely what I mean to convey, and they are not well
> attended to in the modern or classic theories of visual forms. In
> contemporary visual theory we have been content with a rather antiquated
> Gallilean framework in which the arbitrary framework (undone, rebuilt?, by
> Albert) are still substantially in place.

Hmmm. I'll reserve my opinion on this pending seeing the full paper.
The Galilean framework is very close to the Einsteinian one; in special
relativity the only difference is the speed of light; in GR we're really
talking about laws of physics, i.e. dynamics, not simply kinematics
(although that distinction is a bit blurred). You might be surprised
how powerful Galilean relativity really is (when applied properly).
Of course, you might be noting those times that it is not.

> As a matter of appropriate use,  Albert borrowed a perceptually based model
> to found his physics arguments on; ie the tram or gondola perceptual models.
> These models, which John uses in his GAA paper, are equally valuable in both
> physical and perceptual models; but recognition of this has been slow to
> occur. I am willing to risk the criticisms of the physics, and perceptual
> psychology, communities in bringing this long overlooked asset into view.
> These mathematically founded models of theoretical physics can be very
> helpful in perceptual psychology's recognition of an embodied visual form.

Hmm. Can't argue this one without criticising myself. <grin>

> > but by no means the only one. I fail to see any connection between
> > gravitation, though, and the topic of Thomas's paper.
>
> Here is a very important point, and contribution to the argument by John,
> that I did not fully explain. I don't intend to use a gravitational
> 'mechanism' in explaining the form of a binocular visual field, rather, I
> intend to borrow a descriptive technique long accepted in the study of
> physics. The descriptive technique in physics itself, as mentioned above,
> grew out of a perceptual 'thought experiment' (in the tradition of
> Leonardo), which I believe may be appropriate to both physics and perceptual
> matters equally.

Oh, OK. Full agreement with this goal. A few modifiers in the intro
(such as ``*like* the methods used in GR) would make a world of difference,
IMHO.

> We tend to be drawn toward things of interest in the visual field, and place
> what is commonly called the fovea of our vision upon that feature which most
> interests us. This is not a gravity well, which would be appropriate in
> physics as related to inertial frames etc., but descriptively these formal
> structures of perception are similar in character to the notion of an
> inertial frame. Each of us, as we move through our environment focuses at a
> given distance according to our rate. These distances of focus change
> according to our changing rate of movement and mass; in a truck of a given
> mass our focus is further from us due to the unique inertia, compared for
> instance to a bicycle with less mass.

OK. The old ``rubber sheet'' version of GR, eh? Yeah, I think this could
be quite valuable, visual-perceptionally speaking, if it were done well.
I'd probably use different *words* to say what you just said (quite
different, in fact :) but I'm getting your drift. Maybe we could sit
down (over e-mail) and negotiate a common language? :)

> > However, having bagged geometry, both Euclidean and non-, I suppose he
> > would be reticent to put it in those terms :).
>
> I haven't bagged Geometry per se, but feel that where it performs a
> disservice it ought to be reformed.

OK, we disagree about its disservice. Maybe what you were told about
``geometry'' was not the whole story.

> > Disproving mathematics without mathematics?
> > -------------------------------------------
> >
> > Err ... either the question is mathematically describable or not. If not,
> > then the affine transformations were misapplied; if so, then you cannot
> > disprove them by discarding a mathematical description of the world!
>
> In this case the affine transformations were clearly misused, and that is
> demonstrably so. Just as Euclid's projective techniques are inadequate to
> perspectival problems, so are LaGournerie's techniques inappropriate to any
> sort of perspective other than parallel arrangements. DEMONSTRATIONS UPON
> REQUEST; in my studio only (until I can deliver images of a sufficient
> quality to the archives of virtu-l).

:-(  No piccies?  <sulk>

> Mathematics are not discarded by myself, but current techniques are simply
> inadequate to the task. Anyone want to have a go at it?

If I can glean some more details from you via e-mail, I'll give it a burl.

> > Euclidean assumptions
> > ---------------------

[... Tom bags Euclid ...]

[... I bag Tom ...]  :)

> The assumption (in particular) that I wish to question is still in place,
> found in post-Euclidean Geometry, and not necessarily appropriate to
> sensible descriptions of visual experience; the dimensional factoring
> through which Euclid created his cognitive or rational spacial reckonings.
> This is clearly evidenced by the insistence of all physicists and
> mathematicians who claim that we cannot 'fold' time and space into rate.

Seeing is believing ... show me! (OK, it's in the full paper.) A good
physicist will believe anything that makes life simpler; it's only
*mathematicians* that insist on rigorously and blindly following their
forebears.  <grin, ducks from bricks hurled by mathematicians>
Of course, I'm a bit cynical on this one (geez, if I weren't, I'd be
believing in all sorts of things like perpetuum mobiles and cold fusion),
but willing to listen to a good argument.

> FURTHER COMMENTS WHICH WILL HELP ALL WHO HAVE READ THIS ONGOING DISCUSSION

[More details on binocular field projection]

Again, these paragraphs *sound*, at first, like pseudo-scientific ramblings
to people working with physics jargon every day.

However, I am beginning to understand what Tom is on about. It sounds
good. It sounds very good, in fact.

But a warning to science-people: you have to translate his jargon a bit
to fit your own jargonology. Maybe I'll convert him yet. <large grin>

> I intend to support this discussion further by posting a portion of my
> manuscript with the appropriate images to virtu-l archives as soon as I can.

Yeah, gimme, gimme. :) I need some good pictures to get this straight.

John

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John P. Costella              School of Physics, The University of Melbourne
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