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Last updated: Wednesday, October 31, 2001.
An optical illusion arrived in my mailbox today (June 25, 2001):
To try to figure out how it works, I wrote a
little Java applet.
- The applet is here. In some alternate universe where
Java 1.2 is the default, this may actually work. In reality, I have much more luck with the
plug-in version of the applet.
- Still, if that doesn't work, you could just save the class files to disk and run
"java SpinIllusion", assuming you have
the Java 2 run-time
installed somewhere. The class files are:
- Or, you can get the source code and compile/modify it yourself...
The illusion seems to be caused by the image getting bigger and smaller (this can
be seen by the fact that animating the size has the same effect as moving your
head). There are two effects causing the illusion: shape and shading; if you have
no skew, but you do have shading you get the effect, and if you have skew but no
shading you get the effect. These two things seem to cancel each other out if
you leave shading on and make the skew negative. My guess is that the illusion is
the result of the shape or shading somehow making your brain think that when the shapes
move radially out from the center, they also move in the direction of the shape or shading.
If you have a better idea, or a clearer explanation, please
email me. :-)
Here are some more web pages with optical illusions on them:
See also:
Brett Allen
(brett@snazzorama.com)
This page is Copyright 1994-2006, Brett Allen.
