Message #281

From: Melinda Green <melinda@superliminal.com>
Subject: Re: [MC4D] Stereo!
Date: Thu, 15 Jun 2006 23:53:46 -0700

Alright!! This is awesome, Roice. I’m sorry that you can’t see the
cross-eyed stereo yet. It’s quite beautiful in all it’s colorful glory.
I’m sort of surprised that you attempted color anaglyph views because
that loses the colors that you need to solve it, though it’s interesting
what you learned about the background colors. I didn’t know that
although I did know about a related effect that lets you do stereo in a
single projection, but again not preserving color. (See chromatek.com.
They may even still send out free glasses if you ask nicely.)

You asked about instructions for learning cross-eyed stereo. I’ve taught
a number of people. It tends to be easier to learn wall-eyed stereo but
that limits you to very small image pairs whereas when you can fuse
cross-eyed pairs you can use the entire screen. I stumbled onto one page
(http://www.physcip.uni-stuttgart.de/phy11733/stereo_e.html) that has
some very good instructions along with some excellent stereo images to
practice on. I’ll be happy to give more tips if anyone has questions
after trying that page.

It definitely will not damage your eyes to try this but it can cause
headaches if you are not careful. One of the most important things to
watch for is to keep your head perfectly aligned with the vertical axis
of the screen. If your alignment is slightly off, your eyes will try to
compensate which I remember finding very painful in the beginning. Once
you get the image locked in it should be quite comfortable. You may find
yourself falling out of it a lot at first. I recommend cleaning your
screen clean first and keeping the cursor away from the images while
practicing since small differences between the two eye views can attract
the attention of both of your eyes which kills the effect.

At first I thought that your initial stereo separation choice was too
much but after using it for a while and playing with other values, I’ve
decided that it is actually a fairly good default. Here are some
problems I found:

* Orientations in which several rows of stickers line up on top of
another row are difficult to view especially if they have similar
colors. A little rotating fixes this.

* Scaling up the image also causes the images to spread. I think the
centers should stay fixed while scaling, and another slider added to
allow users to set the image separation independently from the virtual
eye separation. (I.E. a purely 2D viewport operation.) This will require
you to clip the parts of one view that extend into the other one. You
might get that for free if you place 2 3D views side-by-side and let the
graphics library or window system do the clipping for you but I would
love to be able to zoom deeper into the puzzle in stereo. Currently when
I try that the views just move offscreen.

* You might want to add a wall-eyed option since it would be trivial at
this point and might be a good option if you have trouble clipping
zoomed in views since wall-eyed works best with smaller images.

* Click-twisting doesn’t seem to work in stereo although I can finish a
twist in stereo that I began in mono.

That’s all for now. Again, great stuff!! This is crazy-cool.
-Melinda