Cannot visualize ground reaction force

[Hao Lee]

Dear all
I am currently working visualizing the ground reaction force with the inverse kinematic data I collected from a vicon motion capture system.
While the inverse kinematic result seems fair, I cannot associate the ground reaction force with it. To be more precise, the software does not error out when I associate the grf, but no arrows are showing when I play the motion.

The model I am using is a modification of gait2392

human_exo_load.osim

(621.79 KiB) Downloaded 87 times

and the inverse kinematic result is

ik_result.mot

(190.94 KiB) Downloaded 84 times

By following the template subject02_grf_HiFreq.mot that comes with the opensim sdk, I believe the ground reaction force mot file I create is valid. It is two forces data collected from two force plates.

grf_data.mot

(661.85 KiB) Downloaded 23 times

While the file has grf more than 1000N, no arrows of force is shown.
Did I do something wrong?

[Thomas Uchida]

Please see the file Resources\Models\Gait2354_Simbody\subject01_walk1_grf.mot (in your local "Resources" directory); the data in columns "ground_force_px", etc. are expressed in meters. In your "grf_data.mot" file, the data in the "F1_px", etc. columns reach >500, so the arrows might be showing up but very far away. The "Motion (.mot) Files" page in the documentation (https://simtk-confluence.stanford.edu:8 ... t%29+Files) might contain some useful information.

[Hao Lee]

That is the issue!!!! Thank you.
I wonder if it is possible to signify the unit's restriction in the documentation.

Units are S.I. units (second, meters, Newtons, ...)
Angles are in degrees.

Are these headers interpretable to OpenSim? Like in trc files, it seems OpenSim can load the unit "mm".
If not, maybe just mentioned that all units are limited to SI instead of putting them in the example of the headers.