1. The shape of a piece of equipment expressed either in height, width, and depth, or in terms of a standard item such as a 3½-inch disk drive or a 19-inch rack.

2. The fraction of radiation diffusely emitted from one surface that is received by another. Form factors are used in radiosity calculations and are strictly geometric quantities whose values depend only on the shape and relative location of the surfaces in the scene. Form factors are independent of view and hence do not have to be recomputed for a change of view.