Problems visualising forces in GUI

[Daniel Gordon]

I would like to visualise assistance forces in the GRF which are not applied in the normal location for GRFs. However, whenever I try to do this OpenSim gets an error. Here's a minimal example.

Steps:

1) Load default gait2392 model from resources folder.
2) Load subject01_walk1_ik file.
3) Associate motion data -> subject01_walk01_grf.
4) Edit motion objects -> edit ground_force_v -> set 'Point Expressed In' to 'pelvis'.

After this step, for me anyway, OpenSim stops playing back motions and an error in the bottom right says 'Component '3DGaitModel2392' could not find 'pelvis' of type component'.

Am I doing anything wrong? Note that I'm just using the default model & data files provided in OpenSim here.

[Carmichael Ong]

The motion files should be associated with the ground frame, so I wouldn't try to express the forces in the pelvis frame. I checked out the gait2392 files, and I'm not sure which motion those GRFs are from, so if you want to try this out, check out the gait1018 model in the Resources folder instead. Steps to do this:

1. Load gait1018's subject specific model (subject01.osim)
2. Load the motion in the IK folder (subject01_walk_IK.mot)
3. Associate motion data subject01_walk_grf.mot