the gap between art and reality. For the artist, a three-dimensional object or
landscape portrayed on a two-dimensional surface merely has to look real. But a model in the computer database must, for all intents and purposes, actually simulate the properties of a three-dimensional object in nature. The single view of an object in a painting or drawing is not enough for an interactive three-dimensional computer-graphics display, which must allow a view of any part of the object, front or back, top or bottom, from any viewing angle in a 360-degree sphere around the object. For this kind of modeling, far more is involved than just presenting the illusion of dimensionality.