Add multiple objects

[yuichiro-student]

Hi, I am using brax as a physics engine. Specifically, I navigate the agents to the goal while avoiding obstacles. What I would like to ask you here is how I can add markers for the target. My idea is to add a sphere.

By google search, I found some examples of adding objects, but they seem to be old and don't support the current version of brax. For instance, when I run one of the code, it says
*** AttributeError: module 'brax.envs.ant' has no attribute '_SYSTEM_CONFIG'.
Would anyone give me hints for adding markers?
Thank you.
example:
https://colab.research.google.com/gist/DavidSlayback/562f800d145a1fa8fbe4c82c27bb9c3f/ant_gather.ipynb#scrollTo=iFRh-5pChDpB

added
_SYSTEM_CONFIG is used only in v1 of the code. Would you tell me what is the corresponding variable and function to add bodies to it?

[erikfrey]

Hello,

Here's an example of adding a target to a an environment used for Reacher. The XML specifies a sphere marker for a body that does not move. Setting contype and conaffinity to 0 assures that nothing can interact with the target, but it can still be moved in code, see this line in the reacher env for an example.

[yuichiro-student]

Thank you, but we don't have a way to add objects in scripts. Is my understanding correct?

[erikfrey]

You can use PyMJCF to programmatically change MuJoCo scenes.