Motioncapture Node is stopping.

[Abhinandan-Krishnan]

Hello, I am using crazy swarms with vicon mocap system.
Intermitently when I run the launch file with launches motioncapture node, I get the "unidentified rigid body" error and thereby the motion capture process is killed.
FOr more context, I am using 5 markers on the quads. Also, there are several other ground robots on the test bed that uses vicon as well running an unrelated experiment.

[whoenig]

I have not seen this error - could you include the full error message? In principle, libmotioncapture has no problem with other robots also being tracked. Please also include with version of Vicon Tracker you are using.

[Abhinandan-Krishnan]

Hello,
Thanks for the reply!
I have attached the screenshot of the error.

[Abhinandan-Krishnan]

Your guess was right, !translation.Occluded and !quaternion.Occludedand were set to true, causing the code to throw that error. I'm guessing it was because of other ground robots which were enabled in the VICON Tracker, but was kept out of sight of the trakcer.

Thanks for the help!

[Abhinandan-Krishnan]

Hey!
I just encountered the same error again. There are not objects tracked in the VICON Tracker. Only one crazyflie that is being used is enabled. The quad fell from the air mid experiment as the motion capture node was killed. The !translation.Occluded and !quaternion.Occluded and were set to true again.

Also, might be helpful to know these,

1. There were ground robots in the VICON's range but they were untracked in the software.
2. The VICON tracker shows a warning, saying the marker configuration it's symmetrical

[whoenig]

I think the logic in vicon.cpp is essentially wrong, since it shouldn't cause an exception just because an object isn't visible for a bit. A try/catch around https://github.com/IMRCLab/libmotioncapture/blob/main/src/vicon.cpp#L73 should work, although is not very elegant.

[Abhinandan-Krishnan]

I'm not sure I fully understand. I am not comfortable with cpp, could you please shed some more light on this?
I am getting this error a lot, and needs to be solved asap. Any kind of help is much appreciated.

[whoenig]

I prototyped a fix at IMRCLab/libmotioncapture#10. Since I don't have access to a vicon system, I need your feedback if it solves your problem.