animating ground forces and muscle forces

[Tim Dorn]

Hi.

I have added my own muscle force data to a text delimited file for opensim to animate. However it doesnt seem to like both ground reaction force data and muscle force data in the same file (I would like to display both on the animation).

If I include both muscle forces and kinetics in the one motion file, the animation only shows kinetics. When i take the kinetic columns out of the file (and modify the header appropiately), only then does the motion animate muscle forces.

Not sure if anyone has actually tried this but it would be great to animate both from the motion file. Could it be an ordering thing? Is there a specific order that the motion file needs to adhere to (i.e. kinematics, then kinetics, then muscle data??) I have tried several combinations with no luck.

Cheers,

Tim Dorn

[Ayman Habib]

Hi Tim,

It looks like the code treats files made up of states as a special case for efficiency reasons so other user objects can't be added to them. I'll look into fixing this but please go ahead and file a bug so that it doesn't fall thru the cracks and you get notified when it's fixed.

The workaround would be to have two instances of the same model, and two motions one with only states, the other with ground reaction forces and then sync. the two motions.

Good luck,
-Ayman

[Andrew Lewis]

Has this been fixed yet in version 2.2?
Thanks,
Andy

[Ayman Habib]

Hi Andy,

We didn't do any work in this area and there was no bug filed AFAIK, the workaround is still there, actually it might be easier now if you use the "Preview Experimental Data" functionality to load GRF and display the muscle forces on the model and use the sync. motions to show them together. If that doesn't work please let us know. Also please file a bug report so we can fix it in the future.

Thanks,
-Ayman

[Andrew Lewis]

Hi Ayman,
The workaround you suggested worked - thanks.
Andy