The third dimension. The apparent distance from front to back or near to far in an artwork. When depth refers to an object's smallest dimension, then this distance can also be called its thickness. When an object or space is principally viewed from above, its depth can also be its height. If an objects's depth is its greatest dimension, then this distance can also be called its length. Techniques of perspective are used to create the illusion of depth in paintings or drawings. Examples of these techniques are: controlling variation between sizes of depicted subject, overlapping them, and placing those that are on the depicted ground as lower when nearer and higher when deeper. Also see aerial perspective, chiaroscuro, direction, herringbone perspective, linear perspective, push and pull, shadow box, sphere, and width.