Feature Request: Only render on change

[gkjohnson]

I'm working with and processing some large BIM assets and often using this viewer to look at the model. Some of the larger BIM models, though, have tens of thousands of nodes and a tone of triangles resulting in a low framerate making it hard to interact with the UI panel, dev console, etc.

Ideally the renderer would only update on change (drag, click, UI toggle, animation step, etc).

[donmccurdy]

PR would be welcome, I think probably the method would be to set up an animation loop for animated models, and otherwise to queue rAF calls only when controls are interacted with.