Chris,

One other thing that Tarun and I thought about was to allow the ability to initialize a VizFrame with either a reference frame and a point, a reference frame and a particle, or a rigidbody. The later two can be use in initialization if you know that you want the default points and/or reference frames of that particle or rigidbody to be used as the reference frame and point for the VizFrame. I don't think that a VizFrame should have an add_rigidbodies method though. There should be one VizFrame per shape where a shape can be a single shape or a collection of sub-shapes that are put together to make a more complex shape.