The C3DAdapter in OpenSim probably won't be able to read the IMU data from the C3D since it can only access Markers and Forceplate data. Can you output the Xsens data as text (.txt) files? We are working on supporting the tracking of IMU orientations, and have been using Xsens data for testing/devel...

Do you have OpenSim 4.0, downloaded from the here? Have you setup OpenSim to work with Matlab and tested that it works?

Also, the C3DFileAdapter only supports marker and forceplate data which is described in the documentation. Is your C3D data from an Xsens system?

Activations are Model states so they get written to the states file of a simulation.

There is documentation on the OpenSim Wiki. However that may be for the most current version (built from source). If you are using the 4.0 downloaded from SimTK, then it will be something like;

We strongly recommend locking those joints. The masses of the bodies in the foot are very small and it can become very difficult to find a ressonable solution. You could see this paper for a description of the problem;https://www.sciencedirect.com/science/a ... 9017303251

This seems like a Matlab/compiler issue and not an OpenSim issue, so I would suggest looking at Stackoverflow or Matlab help sites to try and solve your issue.

Thomas is correct. There will also be an updated version of the OpenSense utilities (including quaternion/rotation conversion) released before the end of the year, so subscribe to the OpenSim email newsletter to be notified of that.

Missing Geometry is not the issue. There is rather large exception pop-up when trying to open the model you posted; Screen Shot 2019-11-09 at 8.07.16 PM.png If you are seeing coordinates being expressed as Radians it is most likely due to this change in 4.0; The MotionType of a Coordinate is now ful...

I would suggest there is something wrong with your model since I can't even open it in OpenSim 4.0

You are most likely performing RRA when not all forces are available. You should only perform RRA during single stance or double support when all forces from forceplates are available.