Problem with inverse kinematics in OpenSim 4.5

[Tereza Kasparova]

Hello,
I am having a struggle with IK on my computer. I am not sure if it is related to the fact that I am using a Mac, but while processing the IK the frames are processed smoothly, and all of a sudden the processing speeds up, resulting in gaps of unprocessed frames that are stuck at a certain value. When I plot the data with Matlab, the final graph has visible gaps. I tried to process the data several times, but the problem persists. My supervisor also checked the trc. data and the model, but everything seems to be fine. So I assume an issue is probably in my computer/OpenSim. I have attached the Matlab-generated figure to illustrate my issue. Have you ever encountered such an issue or could you maybe suggest what could be its cause?

Thank you in advance for any help.
Tereza

[Edward Syrett]

Hi Tereza,
Have you tried breaking up your data into smaller time periods and assessing if that changes anything? Data that lasts 100-250 seconds is an awfully long time. I tend to break up my data to 1 or so gait/movement cycles at at time, after that the data can drift and the errors can increase exponentially. What kind of movement are you examining?

Dan

[Ayman Habib]

Hi Tereza,

I don't think this is a platform specific issue. It's possible some of the frames have Nans or we're having hard time parsing the numbers. I recommend you inspect the first frame where the issue happens for a clue on what's wrong. You can open a trc file in a text editor, it's a tab separated regular text file.

Hope this helps,
-Ayman