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2022-04-29 07:28
Submitted by:
FĂ©lix Lefebvre (felix.lefebvre)
Assigned to:
Nobody (None)
AC contact point

Detailed description

I am a PhD Student in a french laboratory, working on the upper-body kinematics in markerless motion capture.

For now I am implementing a method to create a subject-specific model and I am working with your model of the Scapulothoracic Joint in with the OpenSim API in Python.

I noticed that in the model, the PointConstraint linking clavicle and scapula is directly pointing to a location in the body frame and as a result does not change during scaling ? (whereas it should, because if the body dimension changes, the location of the acromio-clavicular contact point changes in accordance). What it done on purpose ?

I discussed this on the OpenSim forum, and the apparent best solution would be to define a frame in each body at the location of the constraint, which position would be correctly adjusted during scaling, and located the PointConstraint location in body in these frames in position 0,0,0.

Have you ever considered it ?

I looked at the experimental data shared with your model, and the scaled model in it clearly shows the issue as there is a gap between clavicle and scapula bodies as the contact point was not changed and thus is located out of the bodies.

Interested in having your thoughts about this.

Best regards,

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