Cannot create a joint between a body and itself

[lfa1]

Hi,

I am fairly new to Isaac Sim, and while putting a prismatic joint in a linear actuator (that I imported from another world) I came across this error: PhysicsUSD: CreateJoint - you cannot create a joint between a body and itself (both joint bodies must be unique) for joint prim.

While I understand what the error is telling me, I do not get why I am getting this error specifically for this example and not any of the actuators with the same XForm hierarchy I have worked on before this. I have attached a photo of my stage below, and any help would be appreciated, and I am happy to provide any further clarification.

[TomNVIDIA]

Hello, I am moving this topic to the Isaac Sim category for better visibility.

[Simplychenable]

@lfa1 i am not an expert, but perhaps these posts by the mods might be relevant:

USDz import from fusion-360 (cant create joints between different parts of a robot body))

Hello! The errors are pointing that the Joint’s Body0 and Body1 are the same - Can you select the /cypher_base/rear_right_caster_joint and check in the Properties if the connecting bodies are the same or different? Additionally - Joints must be created between Rigid bodies, so you need to ensure that whatever is on Body0 and Body1 have the RigidBodyAPI associated with it (in the properties panel it will have a Rigid Body section). Rigid bodies cannot be nested, but it seems to me you already h…

CreateJoint- no bodies defined at body and body1, joint prim?

Hi, this is most likely because you nested rigid bodies, so the nested rigid bodies were not create. Nesting rigid bodies is not allowed because in USD there is a local transformation stack, so we really dont know the order. To simulate something like this, what you can do is to put both robots on the same level in the USD hierarchy and connect them with a fixed joint. You can either exclude the joint from the articulation (there is a bool on the joint) - this way two articulations will be cr…

also, do you mind mentioning which Isaac Sim version you are using?

[rthaker]

Hi @lfa1 - Here’s the sample example in documentation about how to rig a robot:
https://docs.omniverse.nvidia.com/isaacsim/latest/advanced_tutorials/tutorial_advanced_rigging_robot.html