ClothRay is a patched version of POV-Ray, which allows to do cloth simulation. The cloth is rectangular, and interacts with its environement (gravity, some objects lying, wind, ...). The physical model that is used is described here.
Some animations are available here.
ClothRay is now part of POVMan, a patched version that allows the use of RenderMan shading
For the description of Clothray, follow this way.
For downloading the latest version of POVMan (with cloth patch), follow that way