P3D re: Free Viewing

[Larry Berlin <lberlin@xxxxxxxxx>]

>Date: Thu, 14 Jan 1999 
>From: Paul Ivester <pi@xxxxxxxxxxxx>
>...................
>
>As one of those who, despite years of trying, cannot free view 
>anyting larger than about 1.5 inch centers, I use a viewing aid 
>for stereo web sites.  The cheapest of these is the plastic 
>lorgnette available from Reel-3D Enterprises


Apparently you have only attempted to use parallel viewing. The distance of
1.5 to 2 inches is about the maximum physical limit for most human beings
using parallel viewing. (there are notable exceptions, some on this list are
able to parallel view 3 to 4 inch images. I can do that only if the image is
about 25 feet away.)

However, with the cross eyed method, there is NO size limit. You could place
two giant billboards side by side and freeview them (from the right distance
of course).

I started viewing only in parallel, and out of frustration at only being
able to view small images, I took the time and effort to retrain my eyes to
see cross viewable images. Now I can view both ways, and size is NEVER a
limitation. However, large images displayed for parallel viewing are still a
problem since they can only be seen as pseudoscopic, unless one uses some
additional optical device.

It is a bit difficult to learn cross viewing if you've only used parallel
viewing. This is directly because your eyes have learned which direction the
muscles should pull to maintain the proper eye direction for image fusion.
For crossed viewing the eyes have to correct in the opposite direction and
at first they don't know how. Until you train them in this different
response pattern, they will feel stressed, tired, weird and nigh to impossible. 

The easiest method for learning cross viewing is the finger method. Start
with your finger at the center of the images, and touching the monitor
screen (or almost, so as not to leave finger prints). The rule is, *keep
your gaze attached to your finger* as you bring your finger out from the
screen and closer to your face.

At first you will notice in the background that the two images on the screen
have become four images. DON'T release your gaze from your finger, but DO
learn to notice the background images and keep watching your finger.

Eventually your finger will be somewhere about half way between the screen
and your face. At about this point, the four images in the background will
have turned into three images with two of the original four overlapping one
another. That overlapped center image IS the stereo version you are hoping
to see. DON'T let go of your finger yet though.

The hard part is that if you switch your gaze away from your finger and try
to see the stereo view, your eyes will almost automatically go wide as if to
see in parallel (when you think stereo view, they only know one direction to
go). This immediately causes you to lose sight of your finger and the stereo
image, and contributes to eye tiredness.

If you try too hard, stop and do something else to rest. Later, resume
watching your finger.

To re-train your eye muscles it's necessary to relax your eyes. The ONLY way
to relax your eyes is to view something for which they don't have to strain
or do anything hard. That's why your finger is there. Watch it, and it alone
(no harder than reading a book). As you relax and lock onto your finger you
can expand your awareness without changing the focus of your gaze. Learn to
observe at the edges of your vision, that merged third central image in the
background.

Each time your eye's attempt to SEE that image, it's stress city, and causes
most persons to give up. Don't. Instead keep your finger steady, and keep
watching your finger.

If you have reasonably good vision in both eyes, and you keep up this
exercise long enough, you WILL get to the place where your eyes remain
relaxed, and they don't start stressing out. At some point you will notice
that your finger is in fact floating within the stereo image, since the
convergence point is the location of the virtual image. That's why your
finger is there. To hold your eyes physically at the convergence location,
and do so without stressing out. 

Later, you will be able to briefly switch your gaze TO the stereo view
without losing it, but at first expect that your eye's won't know what to do
and they will only briefly hold the image. With practice AND relaxation, it
gets easier to the point where you can shift your gaze off your finger and
not lose site of the stereo image.

Anytime you lose the image, go back to seeing your finger. This means that
up to now, you don't remove your finger from the viewing area, but are
looking to the side of your finger. Only after you can hold the stereo view
for a few moments do you carefully remove your finger from the area completely.

Keep practicing and you will quickly gain full control over the subliminal
eye muscle movements, the same level of control that maintains ANY sort of
viewing situation. The result is that with a simple mental thought, you can
set your eyes as needed for any size image pair available without undue
effort or strain.

To minimize eye strain for crossed viewing remember to start somewhat
further away from the image than you would for parallel viewing. Remember
the virtual image is much closer to you than the actual screen.

I didn't think I could do it at first either, but it is possible, and well
worth the effort involved. You can freely view BIG pictures in stereo!!!
Look Ma, no optical gizmos!!!

Larry Berlin

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


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