Using this library you can extract and transform markers from C3D files into the OpenSim format and co-ordinate system

Just check out this repository and run

pip install .

To just extract the markers from a C3D/TRC file, you can run the script as follows:

python extractMarkers.py input.c3d --output-file=output.trc

You can also extract and/or rename specific markers using the --markers parameters:

--markers m1 m2 m3=renamedM3 m4=renamedM4

To translate all markers relative to another marker:

--origin_marker m1

To rotate the co-ordinate system around axes defined by markers you can use the --axes_markers parameter. The first argument is the letter of the axes you want to rotate around followed by a pair of marker names:

--axes_markers xy x1 x2 y1 y2

You can also provide the .osim model file to automatically match the markers for rotation:

--osim_model model.osim

To translate between motion capture and OpenSim co-ordinate systems, you can use the --mocap_transform parameter. For known systems (currently only Qualisys), you can put the following:

--mocap_transform qualisys

To define your own translation, put the axes in the order you want them to be swapped as the first parameter followed by the rotation around each axes in degrees:

--mocap_transform yxz 90 180 0

You can also use this library as an imported module in your scripts.

In case of any issues, please feel free to open an issue / submit a pull request.