TRADITIONAL 3-D GLASSES WON'T HELP YOU FIND THE MESSAGE CONCEALED IN THESE
RANDOM DOTS

The blur of random dots on this page conceals a 3-D message. Your job is to se
the message and then decipher it. We'll print the solution in a later issue.

In the past, you could see three-dimensional illusions only when wearing special
glasses with red and green lenses or with polarized lenses to separate "left
eye" and "right eye" images. Or you could put a card between your nose and the
page to separate the two printed images. Computers, however, now allow creators
to make single 3-D images on paper.

Created by computer graphics whiz Dan Dyckman our so-called single-image
random dot stereogram is 980 pixels (picture elements) wide. "First I draw a
strip of random dots, one hundred eighty pixels wide, down the left side of the
screen, with each pixel having a fifty-fifty chance of being black or white,"
Dyckman says. "Then I copy the column of dots one hundred eighty pixels to the
right. Each dot is printed exactly where it was before, except that within a
certain contour-say, a circle-each dot will be shifted one place to the left.
When the image is fused in your vision, the brain will interpret this area as a
circle floating above the background."

Holding the page about one foot in front of you, look at the two circles above
the image. Blur your vision and relax your eyes, as if you were looking at
something several feet away. It may help to blink one eye while your vision is
blurred to split the image.

Each eye should see two circles, for a total of four. Now bring your visual
attention to the middle two. Make them come together and fuse into a single
circle. You will see only three circles and you may perceive depth in the
central circle, as if it were rising out of the page like an overturned
polystyrene cup. It may also feel as if you're looking through the page.

Some people may find it easier to achieve the effect by crossing their eyes. In
that case, the depth images will be reversed.

Having fused the middle circles, maintain your gaze for a few seconds and give
your brain time to make sense of the visual field.

Then gently let your gaze drift down the rectangle. You should now see some
images in the dots.

Don't be discouraged if you can't see depth on the first try. Some people need
only a few seconds before they see it, but most require as long as 20 minutes.
Only a few cannot see it even after a half hour or so.

If your eyes converge the images on the page itself, you won't see any depth.
You must let your eyes diverge "past" the page in order to see the image in the
illusion. It's like looking out a window at the buildings beyond it but still
being aware of what's on the window itself.

When you can fuse the two circles, you know your eyes are properly diverged.
Keep your gaze there and the illusion will appear.

You need the proper divergence, accomplished by fusing the two middle circles.
And you must hold your gaze long enough for your brain to decode the depth
information.

Dyckman has also produced a Macintosh program for making your own images. For
more information, send a self-addressed, stamped envelope (SASE) to Dyckman at
300 First Avenue, Suite 4-B, New York, NY 10009-1844.

N. E. Thing Enterprises also sells poster-sized random dot illusions. For
information and samples send an SASE to One Kendall Square, Building 200,
Cambridge, MA 02139.