Message #286

From: Jay Berkenbilt <ejb@ql.org>
Subject: Re: [MC4D] Stereo! ;))))))))
Date: Mon, 19 Jun 2006 13:13:15 -0400

> It is funny but I can’t see 3D films using glasses!
>
> Everybody enjoys 3D effects during films like Shrek 3D but not me… It’s all
> mixed, red spots are fighting on the screen with green spots and it’s all what
> I see…

I am pretty much the same way, but I may be able to offer some tips as
I have largely successfully taught myself to compensate for my
asymmetrical vision and perceive relatively normal 3D.

I discovered that 3D glasses didn’t work for me when I was about 12
years old and tried to see a 3D movie. A few years later, I was doing
a project for school in which I tried to display some 3D imagery. I
spent hours trying to get it to work and finally gave up, called my
mother in, and asked her to put on the glasses and tell me what she
saw. She saw exactly what I was trying to achieve – it worked for
her but not for me! Around the time I was learning to drive, I became
aware of the fact that I basically had no depth perception. Just as
you can have some sense of relative distances when watching a movie or
looking at a photograph, you can get by without depth perception
pretty much normally for most things and not even realize you’re
missing something, but when you have true depth perception, you can
actually perceive roughly how far away something is even if it is not
in motion or taken in some other context. In my case, my lack of
depth perception and lack of ability to see 3D with 3D glasses of any
type was that I had a prenatal scar on my right cornea which decreases
the visual acuity of my right eye. My left eye, until I was in my
30’s, had better than 20-20 vision uncorrected. My right eye was
somewhere around 20-200 and is only correctable to about 20-40.
People with symmetrical vision generally see with both eyes in the
part of the visual field that is visible to both eyes. In my case, my
left eye saw exactly what it would see if my right eye were closed,
and my right eye filled in some detail around the right edge where
only it could see.

After a few years of work, I was eventually able to achieve normal
depth perception. The first time I flew in an airplane after having
normal depth perception and could see that there were multiple layers
of clouds and the first time I looked over a ledge at a hill below and
could perceive the slope of the hill were magical experiences for me.
I’ve had normal depth perception for 10 years now and I still relish
in it. In order to get normal depth perception, I made one important
change to my glasses (well, my optometrist did…) and also did a
series of exercises. The prescription change I had was to add prism
correction to my glasses. Prism correction is relatively rare, but it
works by having the lenses shift the image from side to side or up and
down. In my case, I had a slight horizontal correction on one side
and a slight vertical correction on the other. In addition to one eye
being dominant, the two pictures perceived by my two eyes were offset
from each other. I used to have some double vision when I was tired,
but I just assumed everyone had that. Normally, my brain compensated
by suppressing one of the images. Since I had the prism correction, I
no longer have double vision even without my glasses, and in fact, the
amount of prism correct I need has decreased over the years. As for
the exercises, I did three different exercises, two prescribed by the
optometrist and one of my own invention. The two suggested by the
optometrist were a convergence exercise and a "brock string"
exercise.

In the convergence exercise, there were red and green circles that
when viewed a certain way were supposed to create a 3D effect just
like any of the 2D stereo vision effects. By using a special
magnifying lens, inverting the card, holding at various distances,
etc., it was possible to strengthen the muscles and get the brain used
to resolving the double image into a 3D image in various
circumstances.

The brock string exercise involves a string that’s about two meters
long with three colored wooden beads placed at different distances.
The exercise there is to hold one end of the string between your eyes,
tie the other end of the string to a distant object, space the beads
out on the string, and to stare with both eyes at each of the beads in
succession starting with the most distant one. Anyone with normal
vision would see one copy of the bead they were looking at and two
instances of the other beads. You would also perceive two strings
crossing each other in a "V" or "X" pattern. In my case, I just saw
two of everything at first, but eventually got to the point where I
could see what I was "supposed" to see. The advanced exercises
involved starting at a bead for a while and then slowly blinking to
see if the converged image can be retained while blinking. At first,
I would have to find the converged image all over again after
blinking, but eventually I was able to close my eyes for several
seconds and still be able to see the converged image. The hardest one
was to look at the bead that’s just a few inches away and retain that
after blinking, but I eventually got to be able to do even that. It
took probably abut six months of doing the exercises two or three
times a week to get to that point. That requires a lot of
persistence, but persistence is probably a trait that any 5D cube
solver has!

The third exercise was one I invented myself (though maybe it’s "out
there") and involved the use of two polarized lenses. I got a cheap
pair of polarized clip-on sunglasses and broke it in half to get the
two separate lenses to play with. If you’ve ever played with
polarized lenses, you know that you can block out all the light by
turning the two lenses at 90 degrees. By superimposing the lenses and
rotating one slightly relative to the other, you can vary the amount
of light that gets through. (There are some interesting things you
can do with three lenses that only work because of quantum physics,
but that’s out of scope for this email!) What I would do with the
lenses would be to block out the light from my left eye so that my
right eye would be forced to fill in the central part of my visual
field. I would then gradually increase the amount of light until my
left eye would "pop in" and start filling in its part of the field. I
think this would happen when about 80% of the light was blocked out,
showing how dominant my left eye was. I would vary the amount of
light until I was right at that threshold, thereby forcing my two eyes
to share in the job of providing the image for the center of my visual
field. While in this state, I would look at a plant on the other side
of the room and try to tell which leaves were in front of other
leaves. I would check myself by moving my head from side to side.
After a few weeks of doing this, I got to the point where I could get
both eyes to share in the job of providing the image with varying
amounts of light. Eventually, I got to the point where I could do it
in normal light without obstructing my left eye at all. Once I could
do that, I actually began to be able to see stereograms for the first
time in my life, though I can even now only see them occasionally, and
I have to stare at them (or past them as you really have to do) for
several minutes. The way I learned to see those was to put the
stereogram behind a piece of glass (like the glass from a picture
frame) and shine a light on it so that the point of light glared on
the glass. If I could see two dots of light instead of only one, then
I knew that both eyes were working. At first, I would only see one
dot of light because my right eye was not doing its part. The best
way for me to see stereograms is to view them through glass with a
light shining on the glass. I start by focusing both eyes on the
reflection of the light so that I see a single converged image. Then
I relax my eyes and let the dot of light spread into two so that I’m
focusing on something more distant. Eventually this way I can usually
see the stereogram.

Maybe you can try exercises like this and eventually teach yourself to
see 3D and enjoy stereo effects. It took me a long time, but the
rewards were worth the wait and the effort. Either way, I hope this
was at least somewhat interesting. :-)

–Jay