gz-sim: detachable_joint.sdf

[azeey]

Setup

• Os: Ubuntu Jammy
• BuildType: Binary

Links

• Source

Checks

• Instructions work
• Images (if there are any) match the result

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You can find the code used to generate this test case here

[JACOBIN-SCTCS]

The state of the breadcrumb isn't getting monitored properly for this simulation. Only after I did a reset did the state of a breadcrumb appeared. Was this the expected behaviour (Attaching video). Can somebody also verify too.

detachable_joint-2023-09-07_21.49.58.mp4

[Voldivh]

I got the exact same behavior. Could you take a look at it @ahcorde ?

[iche033]

I think msgs are published to the state topic only if there is a change in state (attached -> detached or vice versa) as opposed to periodic updates.

Regarding reset causing a msg to be published on reset, that probably revealed an issue. It seems like an extra detachable joint is created whenever reset is invoked. It could be a bug.

[Voldivh]

I think msgs are published to the state topic only if there is a change in state (attached -> detached or vice versa) as opposed to periodic updates.

Yep, just tried it out and works as you explained. Thanks.

Regarding reset causing a msg to be published on reset, that probably revealed an issue. It seems like an extra detachable joint is created whenever reset is invoked. It could be a bug.

After playing a little bit around with it, the behavior does seems weird. I'm not sure if I understood what you mean by "an extra detachable joint is created...". The msg I received is related to the joints that were part of the simulation before:
Video

[iche033]

I was looking at the terminal that's running gz sim. Everytime I press reset, I see the msg:

[Dbg] [Physics.cc:1864] Creating detachable joint [53]

The entity number ([53] in the above example) keeps increasing so I assumed that new joint entities are created.

[Voldivh]

Oh, I'm getting something different when I click reset:

Msg [NameManager::issueNewName] (Skeleton::Joint | vehicle_blue) The name [fixed] is a duplicate, so it has been renamed to [fixed(1)]
Msg [NameManager::issueNewName] (Skeleton::Joint | vehicle_blue) The name [fixed] is a duplicate, so it has been renamed to [fixed(2)]

[ahcorde]

can you try this patch ?

gazebosim/gz-sim#2131

This should reattach the models again

[azeey]

Closing since PR has been opened