Re: SAY YES TO "PSEUDO"!

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>Date: Mon, 3 Feb 1997 13:30:44 -0500 (EST)
>From: P3D Dr. George A. Themelis writes:
>
>Larry seems to believe that a pseudo stereo is every bit as natural as a
>normal stereo and it is only our lack of familiarity with the visual
>experience that gives us troubles.  This view, IMO, fails to acknowledge
>the strong effect that monocular cues have in "seeing" depth.  

*******  Of course they have a strong effect. Their effect combined with a
mind used to interpreting them in a certain way cospires to make the initial
experience of pseudo stereo somewhat confusing. I've been beyond that point
so know there is meaning on the other side of the confusion.


>
>Most scenes, either real or artificial, have monocular depth cues that
>coexist happily with stereopsis.  In a pseudo stereo these cues conflict
>stereopsis.  The image we finally "see" and the degree of our confusion
>depends on how these monocular clues interact with the depth reversal in a
>pseudo.  

******  To a point. You are assuming the confusion is impossible to get
beyond, and it is not. There are images that are too complex to be
satisfying, but all of them can be viewed this way if you choose to do so.
The mind is capable of understanding the *conflicting* cues. The biggest
problem is that patterns we associate with something behind, is now in
front. The mind actually continues to *seek* it's placement in the mental
construct as still behind the key objects, resulting in an internal *does
not compute* which is felt as confusion. If you carefully follow the real
correlation and come to understand where the textures are now located
spatially, confusion disappears. The confusion is caused not by the reversed
image but by a mind not used to viewing in this fashion.

>
>It is interesting to see how our brain deals with this conflict.  But it is
>a stretch to say that this conflict is a natural event.

******  What's unnatural about it? It totally follows all laws of physics.
It is only in the mind where a normal outlook is maintained that the
interpretation falls down with experience of the unusual. Natural and
unfamiliar happen together all the time but things in nature we didn't know
about before aren't automatically classified as unnatural just because we
are not familiar with it. *Unnatural* is reserved for things like plastic
that don't exist in nature.

>
>Take for example a computer wire model of a cube..........
>Let's introduce linear perspective ................
>The sides of the cube that are closer to the observation point
>appear now larger.  If we reverse the pair we will now see an object of
>unequal sides.  The sides that are closer to us are smaller and the sides
>that are far away are larger.  This is _not_ a cube in my geometry books
>and I see nothing indicating "bogus science" (even with smileys) here.

*****  George, when perspective is reversed we expect to see these changes.
The cube still remains a cube. It is perhaps difficult to grok the
inside-ness of things, but that is what is represented in a pseudo-stereo
image. The quality of inside-out is different and more complex than simple
reversal.

>........
>At the end, the stereo pair is a representation of either a real physical
>object or a model of a physical object.  There is a definite choice of
>what is right and what is left.  Even in the case of the simple cube wire
>model without any linear perspective, the creator has selected the
>appropriate observation point.  The reversed image while not in conflict
>with any monocular depth information, still is not the one originally
>created.  While there is depth information in the reversed image, this is
>opposite to the depth information in the real scene so it is justified to
>call it "pseudo" meaning "false", as opposed to the real or true image/
>model.

******  Keep stretching!!!   ;-)  The choice of left and right is based on
the familiar. Regardless of this choice the opposite arrangement exists,
always. The reversal of the left and right results in an inversion of the
stereopsis and thereby reverses the direction of the depth cues. A
pseudoscopic pair is by definition one and the same as what was originally
created. This inside out nature of the reversed stereopsis isn't grounds to
call the phenomenon false or fake which seems to imply it doesn't exist or
misrepresents the relationships within the image. It is different, it is
inverted and I understand how in one limited sense this is *false* by
comparison strictly to normal vision parameters, but it ignores and
misrepresents the full geometric symmetry involved. (a problem for many
common terms)

Larry Berlin

Email: lberlin@xxxxxxxxx
http://www.sonic.net/~lberlin/
http://3dzine.simplenet.com/


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