Art of Illusion is a powerful Java-based 3D modelling and animation tool.
Models can be constructed from cubes, spheres, cylinders, curves, spline and triangle meshes and more. You're able to define materials, edit textures and surface properties, then create photorealistic images with motion blur, depth of field and more,
Sequences of still images can be exported for use elsewhere, or exported as a .mov video, and there's support for skeletons using forward and inverse kinematic animation.
Support for scripting via the Beanshell language allows the program to be extended in various ways, at least in theory. Art of Illusion comes with a few of these - including one which applies fur to a model - and you should be able to add more, although the default repository didn't seem to be working when we tried it.
Figuring out precisely how all this works will take plenty of time and effort, but the website's "Art Gallery" of amazing sample images shows what can be done, and there's a manual, forum and various tutorials to help you get started.
Version 3.0.3 (Changelog):
A powerful, comprehensive and extensible modelling tool.