Rescaling model per activity

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Emily Hubbard
Posts: 7
Joined: Sat May 06, 2017 2:17 pm

Rescaling model per activity

Post by Emily Hubbard » Wed Aug 16, 2017 3:46 pm

Hi all,

My question regards rescaling a model after receiving results from IK. After scaling a model in static pose, do you know why you would or would not want to rescale the model after running IK on a walking trial to get better results in the next iteration of IK? I have associated the trc file of blue marker data from the walking motion. I use that to move the pink markers on the model closer to the blue markers. I do that until my max marker error is between 2-4 cm for each segment of IK.

Another question, is it reasonable to rescale a model for each activity it preforms to achieve "good" results in IK?

Wondering if there could be a negative impact on results from the inconsistency of this. Any input is appreciated.

Thanks,

Emily
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Thomas Uchida
Posts: 1792
Joined: Wed May 16, 2012 11:40 am

Re: Rescaling model per activity

Post by Thomas Uchida » Thu Aug 17, 2017 4:36 am

In most cases, there will be at least some uncertainty about where exactly the markers should be placed on the model. It is reasonable to adjust the marker locations within this region of uncertainty; some optimization algorithms to do this can be found in the literature. Strategies for improving scaling are also discussed in this webinar: "OpenSim Webinar: Tips and Tricks for Data Collection, Scaling and Inverse Kinematics in OpenSim" (https://www.youtube.com/watch?v=ZG7wzvQC6eU).
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