Interactive Visualizer

[erikfrey]

Brax's visualizer currently only renders static rollouts of pre-processed physics updates. We would also like to be able to visualize physics updates "on-demand" for at least two scenarios that we can imagine:

• Pass a policy to the visualizer instead of a trajectory, so that it can unroll forever
• Allow the user to interact with the trained agent (push it over, throw a box at it, etc)

For this to work, we would embed Brax into an http server that the js client communicates through. Colab can host an http server, but the latency is poor - so rather than be 100% interactive, we may have to "batch" physics steps to keep the visualization smooth.