Impossible fractals

Impossible objects are a type of optical illusion involving ambiguous visual descriptions of figures that cannot physically exist. It is shown by way of example that such objects can be further developed using standard fractal techniques to create new, more complex designs that retain the perceptual illusion, sometimes allowing additional illusions to emerge from the process. The balanced Pythagorean tree is used to efficiently render impossible fractals that display the perceptual effect across decreasing levels of scale. r 2007 Elsevier Ltd. All rights reserved.