Sketch is a small, simple system for producing line drawings of two- or
three-dimensional solid objects and scenes. It began as a way to make
illustrations for a textbook after we could find no suitable tool for
this purpose. Existing scene processors emphasized GUIs and/or
photo-realism, both un-useful to us. We wanted to produce finely wrought,
mathematically-based illustrations with no extraneous detail. The input
language is reminiscent of PSTricks, so will be easy to learn for current
PSTricks users.

WWW: http://www.frontiernet.net/~eugene.ressler/