As much as I despise the deliberate campaign by mid-20th Century modernist art critics like Clement Greenberg and Harold Rosenberg to denigrate the history and traditions of western art in order to elevate their own pompous theories (in the process killing realism for half a century), I will grant that they were correct about one thing.
Representational art is an illusion.
It is the illusion of a three dimensional scene or object created by the arrangement of paint or other marks on a two dimensional surface.
With that in mind, most artists should at least have a passing interest in vision, optics and the fascinating subject of optical illusions. (Proponents of the modernist doctrine of flatness are, of course, excused and may go sit in the hall for the duration.)
I’ve featured some optical illusions in the past, such as the calculated space-altering architectural patterns of Felice Varini (images at left, top), the anamorphosis in Hans Holbein the Younger’s The Ambassadors and the anamorphic sidewalk art of Kurt Wenner (left, middle) and Julian Beever (left, two bottom images).
Here are some general interest optical illusions blogs and sites of varying quality and subject matter. They are at the very least fun to poke around in, and at best can be genuinely illuminating.
Of particular interest to artists should be optical illusions that deal with color and dramatically demonstrate how utterly and completely the perception of color is affected by the surrounding colors.
Notable in that respect is this series of color perception experiments on eChalk, which are the most striking examples of that principle I have ever seen.