Welcome to the Cuboid Demonstration. On the left you should see an applet whose contents displays a cube. Click on [Start] to rotate the image. The scrollbars will allow you to change the tilt, slant, and speed. Also, you can change the tilt/slant by clicking on the center on the rotating image and drag the mouse.

A slanted picture of a cube does not look like a cube despite the presence of depth cues (shading, texture, binocular disparity). This phenomenon can be explained by the operation of a priori constraints in the visual system. In the case of shapes of polyhedra, the visual system minimizes the departure of contours from planarity and the variance of interior angles. As a result, when a slanted picture of a cube is rotated, the observer perceives a non-rigid cuboid, rather than a rigid picture of a cube.

An MPEG video illustrating this illusion is also available. Click here to get it.

Last updated: 6/27/1998
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(C) 1998 Filip Pizlo, pizlo@iquest.net