Scale Tool enforcing static pose

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Tom Augenstein
Posts: 38
Joined: Thu May 03, 2018 8:19 am

Scale Tool enforcing static pose

Post by Tom Augenstein » Mon Mar 01, 2021 9:06 am

Using the Gait2354 model, I'm playing around with the marker positions to see how it changes the resulting scaled model. I tried shifting the knee markers far forward (R.Knee.Med and R.Knee.Lat 30 cm in the positive x-direction), but for some reason the resulting model has a knee angle of (exactly) zero with a longer thigh and shank. Why doesn't it return a static pose with a longer thigh and shank and a bent knee? Based on the "Marker Placement" section on the "How Scaling Works" page, it seems like I should get back a bent knee?

I'm shifting the markers forward, so there shouldn't be any conflict with the joint limits, plus I disabled all other thigh and shank markers, so the only input should be from the knee markers.
Tags:
OpenSim 3.3 and Earlier
Windows
GUI
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Carmichael Ong
Posts: 401
Joined: Fri Feb 24, 2012 11:50 am

Re: Scale Tool enforcing static pose

Post by Carmichael Ong » Thu Mar 04, 2021 11:41 am

Looking at the scale setup file, it seems that even if you remove the thigh and shank markers, you have markers still at the foot to track. These would still affect the knee angle too (I wonder if you moved them "up", then the knee might flex to match). It might also be possible that the optimizer is stuck in a local minimum too.
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