Virtual markers in trc file

[Mahshida hamid]

Hello all
I have been trying to scale my model. I am using motion capture to record the human walking and now i am trying to scale it using the rajagopala model, my model uses 43 markers for the scaling purpose yet it is not improving , my RMS error is 0.08 which is quite large. i WANT TO USE VIRTUAL MARKERS BUT HOW DO I CREATE VIRTUAL MARKERS IN TRC FILE THATI CAPTUED FROM THE MOTION CAPTURE?
any help and leads would be appreciated

[Karolina Saegner]

Hello. You should use your static .trc file during the scaling, however you need a separate marker file (.xml file) which contains virtual marker positions. As scaling is an iterative process, you need to adapt your virtual marker positions to match those of the experiment. You can do this with checking 'preview static pose' box in the scale tool. After doing so, you can upload your experimental static file (.trc) through 'Associate motion data' with right clicking on the 'static pose' in the motions (in the navigator). You will be able to see how far off are your virtual markers compared to experimental ones and adjust their location accordingly.

Hope this helps.

[Mohammadreza Rezaie]

Hi, TRC files can be opened and edited in Excel in which you can create some virtual markers such as knee/ankle joint centers (the average of the medal and lateral markers). Hip joint center calculation however, is more complicated. If I remember correctly, MoToNMS handles it:
https://simtk.org/projects/motonms
Hope this helps.