Hello, I'm trying to understand the meaning of the various quantities gathered in the observation space of some advanced environment like Humanoid, namely: - data.qpos.flat - data.qvel - data.cinert - data.cvel - data.qfrc_actuator - data.cfrc_ext Most of them are pretty clear to me, but not 'cinert' nor 'cvel'. According to the documentation, 'cinert' is "com-based body inertia and mass (nbody x 10)" and Todorov said on another post that it corresponds to "the mass and inertia of a single rigid body relative to the com of the subtree to which the body belongs". I get this more or less but more information about this quantity would be helpful. Regarding 'cvel', the only description I could find is "com-based velocity [3D rot; 3D tran] (nbody x 6)". I don't understand the meaning of the rotation part, since for me the center of mass is a position only. Besides, for both quantities the frame in which they are expressed is not mentioned, which is problematic. I know that those quantities "are intermediate results that were not meant to be documented and exposed to the user", as Todorov said, but since it is a key feature of extremely important benchmark in the field of reinforcement learning, it is very critical to make sure everybody can find extensive information about them.