Best way to spawn objects to move around?

[benthebear93]

Intro

Hi!

I am a graduate student at SDU Robotics, I use MuJoCo for my research on contact manipulation.

I am trying to spawn objects that i can move with robot manipulator.
Usually i just add the object body with freejoint.
I am also using mjcf from dm_control which asks for initial qpos
arm_mjcf.keyframe.add("key", name="home", qpos=HOME_QPOS)

My setup

MuJoCo 3.2.0
Python
Linux 22.04

My question

Although I could specify the joint positions for objects directly, things get quite messy when I want to spawn multiple objects or use an IK solver like mink, because the IK solver will give you a solution for every joint.

Everything makes sense logically but it doesn’t seem ideal to me. Is there a better way to spawn objects that can move withoug adding extra qpos?

Minimal model and/or code that explain my question

No response

Confirmations

• I searched the latest documentation thoroughly before posting.
• I searched previous Issues and Discussions, I am certain this has not been raised before.

[yuvaltassa]

No. The answer is in the question "adding objects that can move" == "extra qpos"

[benthebear93]

Okay thank you for the answer :)