The Mathematics of Three-Dimensional Manipulations and Transformations. Edition 1.1, by Trip V. Reece, June 1992.
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Although the title for this entry appears stultifying, indeed formidable, it is little other than identifying the relationships between distance and perspective. The most important concept in 3d display is the apparent shrinkage of objects as they recede. The other concept to keep in mind is the idea of a vanishing point. The goal of this mapping function is to be able to pass it the three-dimensional coordinates and have it return the two dimensional coordinates for the monitor screen. Imagine now, if you will, another, perfectly identical sheet of plastic exactly 3cm from the first, parallel to the first and further away from you than the first.