Rendering utilities

[vincekurtz]

We should have some tools for making nice videos. The MJX tutorial has a basic rendering example, but it's awkward to implement and the resolution isn't very good.

[pculbertson]

Might be worth the effort to stand up the Unity plugin for MuJoCo + create some standard scenes

[alberthli]

Towards Unity: for whoever ends up picking this up, here are some useful links:

• Installing Unity Hub to manage different Unity distros: https://docs.unity3d.com/hub/manual/InstallHub.html#install-hub-linux.
• Instructions for integrating MuJoCo with Unity: https://mujoco.readthedocs.io/en/stable/unity.html