Sketch 
(c) 2005, 2006, 2007 Eugene K. Ressler

Sketch is a simple system for producing line drawings of 
three-dimensional 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 and be able to easily overlay TeX math and text. The input 
language is reminiscent of PSTricks, so will be easy to learn for 
current PSTricks users.  It generates either PSTricks or TikZ/PGF
code as output.  See http://www.frontiernet.net/~eugene.ressler .