Linderdaum Engine is an open source purely object-oriented 3D gaming engine written in C++. It is designed to be an integrated solution for the development of interactive 3D applications, for game, industrial and scientific visualization.
Slut is a programming framework for generative, synthetic, interactive, network-enabled graphics. THIS IS AN OLD PROJECT. But since you are interested in it you should check out the SceneExpression project: http://labs.nortd.com/sx/