Three-Dimensional Plotting Functions

The PyGist 3-D graphics uses the PyGist 2-D graphics to draw its pictures; most of the 3-D routines are computational, and take 3-D 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 3-D PyGist is

• retrieve or compute your data;
• tell PyGist orientation and lighting information;
• call the appropriate PyGist computational routines;
• call one or more PyGist 3-D plotting routines;
• call the master function draw3, which actually displays the graph.

  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 3-D 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.