Reason for MjxEnv

[Balint-H]

Hello, and many thanks for releasing this awesome project.

I was just curious, previous MJX environments used brax's PipelineEnv as the base class. What were the reasons for reimplementing a lot of its functionality with MjxEnv (apart from using only an MJX backend of course)?

[btaba]

We wanted to get rid of the brax dependency (legacy data structures and legacy XML parsing logic) for code that primarily uses MJX.

[btaba]

We also tried to be a bit agnostic to the RL library (RSL-RL examples are provided), although we primarily used brax.

[Balint-H]

Makes sense, thanks!