Clayworks is a 3d modelling program written by luther The original shareware program was released in 1994 and a greatly enhanced new 32bit version will soon be available (in y2k).
Clayworks was originally designed as a simple polygon modelling tool but now supports curved surfaces, metaballs, animation advanced texture mapping and particle effects.
see http://members.aol.com/luther2000/clay.htm for more info.