Rectus femors of a model is displayed differently in Opensim 3.3 and 4.1

[Will Bosch-Vuononen]

Hello,

I have been modifying a model in order to return better predictions of the knee contact forces. I have started the modifications in Opensim 4.1 but recently changed to Opensim 3.3 because the rectus femoris behaves as expected in 3.3 but in 4.1 the visualization is quite odd (see pictures attached). Please note that both models have the same wrapping surfaces and the attachment points of the muscle were not altered (neither extra ones were added). Would there be an explanation for such difference in the visualization for the same model in different versions of OpenSim?

[Thomas Uchida]

There was a visualization bug in 4.0; this may be related. You might try plotting the muscle moment arms to see whether the issue is strictly visualization or whether the muscle path is being computed incorrectly.

[Will Bosch-Vuononen]

Hello,

thank you for your reply! When plotted, the moment arms and muscle tendon lengths are the same for both versions. I just wonder now whether the problem is strictly visualization...

[Ayman Habib]

Hello,

Yes, the problem is strictly visualization, some corner case(s) that could be related to the current pose, how you defined the path-wrapping and the type of wrapping objects. If you can provide a minimal model and describe how to reproduce that would be great.

Thanks for reporting,
-Ayman

[Will Bosch-Vuononen]

Thank you for the clarification! This doubt had been pending for some weeks... I will contact you.

[Will Bosch-Vuononen]

Hello,

here is the simplified model, in 3.3 and 4.1 version.