Used to describe the three-dimensional axes set at right angles to each other, available in DVE manipulations. At normal (clear) x lies across the screen left to right, y up the screen bottom to top and z points into the screen. Depending on the power of the equipment and the complexity of the DVE move, several hierarchical sets of xyz axes may be in use at one time. For example, one set may be referred to the screen, another to the picture, a third offset to some point in space (reference axis) and a fourth global axis controlling any number of objects together.