Open Shading Language (OSL) is a small but rich language for
programmable shading in advanced renderers and other applications, ideal
for describing materials, lights, displacement, and pattern generation.

OSL was developed by Sony Pictures Imageworks for use in its in-house
renderer used for feature film animation and visual effects. The
language specification was developed with input by other visual effects
and animation studios who also wish to use it.

WWW: http://code.google.com/p/openshadinglanguage/