The PyGist 3D graphics uses the PyGist 2D graphics to draw its pictures; most of the 3D routines are computational, and take 3D data in one form or another and massage it until, when plotted, it will appear to be a correct two-dimensional projection of a three-dimensional graph. The usual order of operation in 3D PyGist is
PyGist builds a list of information about the graph which you wish to plot, but in its normal operating mode, does not actually draw the graph until you ask it to do so, by invoking draw3. Meanwhile, it stores the information about the graph in a Python list. In this chapter we shall describe the contents of this list in general terms, and the commands which you use to build it (orientation and lighting functions); the setup functions for complicated 3D plots; and the plotting functions themselves. In a final section, for people who may some day be maintaining or adding to this code, we describe the auxiliary functions which everyday users will seldom if ever use.