I'm using MuJoCo via OpenAI Gym. The XML files have group=<some number> attributes. I can't find anywhere in the documentation a description of what effect each value for group has on object visibility and other behaviours. e.g. if I change the group for a site from 4 to 1, it may become visible, but will there be other consequences?
Groups are only used for visibility by mujoco, but you can use them for other things as well -- it is convenient way to label objects with an integer. Note that you can also define user parameters, and have more than one user parameter per object.
Thanks very much. As a Gym + mujoco_py user I wasn't clear if "group" has a fixed interpretation or is user-defined. Anyway, changing the group to 1 for class="robot0C_Hand" had the desired effect of allowing me to see all capsules in the Hand model, so this is resolved.