Fluxus allows you to write Scheme scripts that create graphics live, interpreting audio and OSC input as a source of animation data. Fluxus also uses a fully featured physics library, which means you can script physical properties into objects and simulate them in realtime. Released for Linux under the GPL licence.
The built in scheme code editor runs on top of the renderer (see screenshots), which means you can edit the scripts while they are running. This allows Fluxus to be used for livecoding performances, or simply as a fast feedback way of experimenting or learning about graphics and animation.
Fluxus lends itself to procedural modelling and animation, there is no model import functionality, only simple primitives. There is an experimental procedural modelling tool however, and full support for texturing and basic material properties.