Heaver: A Visual Illusion

The applet below is a demonstration of an optical illusion. In its original form as conceived by professor Misha Pavel of the Oregon Graduate Institute, a rotating square is occluded by four other squares that leave a cross-like opening to view the motion. Look at the applet. The impression you are supposed to get is that the square periodically expands and then shrinks and then expands again. A similar illusion is achieved when a rotating triangle is being occluded by six triangles forming a hexagon (Suggested by Arthur van Houdt.) The occluding shape may also consist of 4 or 5 triangles and matching rotating shapes. When occluding and rotating shapes do not quite match the effect is very different.


The only browser that currently runs Java applets is Firefox where, too, you have to make the site cut-the-knot.org trusted in the Java setup

Heaver Illusion

This one is really best watched in a dynamic applet.


What if applet does not run?

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