Note: These images and pages describe an old software package called Partman, written at Cinesite. To my knowledge, the software was last used on Xmen 2, and I do not know if it exists anywhere today. Partman was a renderer focused on a very specific problem: render as many unresolved particles as possible in as little time and memory as possible. It also included a kind of shading language, written by Phil Graham, to generate particles procedurally on the fly. Because of Partman's odd statistical method of rendering, this meant that only one particle needed to exist at a time, producing very low memory requirements.
Rendering Lots of Particles Using Partman
The highly flexible Perl-based version of partman.
A document on a collection of tricks and tips for creating particles with the pdbEditor emission language.
A small gallery of abstract images rendered with partman.
The HOW-TO guide for the stand-alone partman executable.