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Snowden, Thompson and Troscianko: Basic Vision (revised edition)

Chapter 07

Dragon Illusion


A version of the hollow-face illusion. As you move your head (or walk around) the dragon’s head appear to track you. The illusion is caused by your (mis-)interpretation of the dragon’s head. The head is actually concave (sticking in) , but you naturally see it as convex (sticking out). As you move your head this caused movement of the image on your retina which you know about and normally can cancel so that stationary things appear stationary. However, your mistaken belief about the shape of the head means that this cancellation does not work, and the head of the dragon appears to move.

A similar trick here is the floating cube – it also should show you how easy it is to produce your own version!

Ames Room


A short film showing Ames room and how it is constructed.