Kinetic art expressions based on optical and luminous phenomenon as well as painting illusionism. The expression "kinetic art" in this modern form first appeared at the Museum für Gestaltung of Zürich in 1960, and found its major developments in the 1960s. In most European countries, it generally included the form of optical art that mainly makes use of optical illusions, such as op art, represented by Bridget Riley, as well as art based on movement represented by Yacov Agam, Carlos Cruz-Diez, Jesús Rafael Soto, Gregorio Vardanega, or Nicolas Schöffer. From 1961 to 1968, GRAV ("Groupe de Recherche d’Art Visuel") founded by François
Geometrical-optical illusions show up in ordinary black and white line drawings. A few examples are drawn from the list of optical illusions. They illustrate illusions of position (Poggendorff illusion), of length (Müller-Lyer illusion), of orientation (Zöllner illusion, Münsterberg illusion or shifted-chess-board illusion and its café wall illusion variant), of rectilinearity or straightness of lines (Hering illusion), of size (Delboeuf illusion) and of vertical/horizontal anisotropy (Vertical-horizontal illusion), in which the vertical extension appears exaggerated. Visual illusions proper should be distinguished from some related phenomena. Some simple targets such as the Necker Cube are capable of more than one interpretation, which are usually seen