Importance of Occluders: Motion Binding


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Importance of Occluders: Motion Binding

This one is really best watched in a dynamic applet.


What if applet does not run?

A few words.

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Copyright © 1996-2017 Alexander Bogomolny

Depending on whether you hit the Start button right away or after trying other controls, you will see either a wobbling regular n-gon (a square at the outset) or a combination of moving, stretching and shrinking line segments.

The applet is an adaptation of the one illustrating Gerbino's illusion where an object was stationary and the occluders rotating. Here the object rotates while the occluders are stationary. However, when the color of the occluders is that of the background, i.e., when the occluders practically disappear, the object loses its identity and the observer only sees pieces of a few line segments.

In the absence of occluders the line segments appropriate their endpoints so that we do not see them extended to the vertices of a coherent object. The phenomenon is known as Motion binding.

A similar effect is illustrated by the Heaver, an illusion discovered by Misha Pavel.

References

  1. M. Bach, Motion Binding

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Copyright © 1996-2017 Alexander Bogomolny

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