I've always been fascinated by <span class="bold">anamorphic illusions</span>.  Here are four examples I've found in a book titled " <span class="bold">Optical Illusions: The Science of Visual Perception</span> " :



Transformation illusions:


<span class="bold">Encore</span>  (Shigeo Fukuda  ―  1976)

From one angle, the sculpture depicts a pianist. But if you turn it by 90 degrees you'll see a violinist. "Encore" is part of a series of metamorphosing musicians captured at different stages of a concert.


<span class="bold">Underground Piano</span>  (Shigeo Fukuda  ―  1984)

This distorted structure creates the illusion of a perfect piano when it's reflected by the mirror.



Shadow illusion:


<span class="bold">Lunch with Helmet On</span>  (Shigeo Fukuda  ―  1987)

This shadow sculpture of a motorcycle is built entirely out of welded forks, knives, and spoons. Fukuda wanted to create a three-dimensional object in which the shadow, as opposed to the actual form, represented the actual object. He utilized 848 pieces of cutlery to construct this work.



Anamorphic painting:


<span class="bold">Endlich auf der stra&szlig;e. Der Smart ForFour</span>  (Edgar Müller, Manfred Stader and Gregor Wosik  ―  2004)

Another great example of anamorphosis is an outdoor advertisement for the Smart ForFour, created by three street painters in Hamburg. This anamorphic painting is 82 feet long.