Kokichi Sugihara
An “impossible motion” is a new type of optical illusion, in which a
given three-dimensional object seems to have an ordinary shape, but
motion added to the object gives us an impression that something
impossible is happening; for example, a ball rolls uphill defying
the gravity law, and a bar passes through windows in an inconsistent
orientation. What is actually happening is that the motion is
physically natural while the perceived object shape is different
from an actual shape. This class of illusion solids can be designed
with the aid of shape-from-image equations. This illusion is strong
in the sense that we cannot avoid the illusion even after we
understand the true shape of the object.