The use of perspective and pictorial techniques to create works out art which create the illusion of reality. Illusionism was a principle in Roman wall painting and relief sculpture. Light and shadow is being represented so as to create the illusion of depth. No formal geometric system for creating perspectives was known to the Romans, but they were adept at using aerial perspective to create the notion of recession in the murals. Centuries later, in the renaissance and baroque, a more formalised approach to geometric perspective was added to illusionism.