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Hello,
I am working with OpenSim recently and I am trying to scale a generic model.
After opening Scale Model... window and loading scaling setup, in the second Tab ( Scale Factors)
there are these factors each related to the one segment. I almost know what they are for but, I don't know how they have been calculated.
Does anybody know how these factors have been calculated or where they come from?

Thanks!

Hi,

There is this nice tutorial about scaling tool:

https://www.youtube.com/playlist?list=P ... 29007D54F6

Also, you can read the user guide:

http://simtk-confluence.stanford.edu:80 ... im/Scaling

Regards

Hi Firooz,
I'll try to answer you based on what I know, though what I do know is based on the examples in the files of the tutorial Jim mentioned (since the 'setup' tutorial mostly just says "load our settings and hit run") and some of the stuff I've been doing for my own work.

Basically, according to available documentation, those scaling factors are determined by comparing the distances between different markers across the model you have loaded and the one you are attempting to scale to. So, the former is simple enough - you have that model loaded, and can see the markers on it, and all of their names. But to get the lengths of various segments of the model you are trying to fit, you typically (in my experience) need to manually create the segments by clicking "Edit Measurement Sets" (it looks like you did click that at one point). There, you can name the segments you wish to use, and then choose the markers its measurements rely on. For example, if I wanted to set up a measurement for the thigh, I'd give it two segments: one from the right pelvis (RASI in my model) to the right knee (RKNL in my model)and another from LKNL to LASI (left knee to left pelvis).
Once your measurement sets are determined, you can select each body name you wish to scale in the "Scale Factors" tab by using the drop-down menu to select the set to scale a selected body to (all three should fill in with the same choice; your guess is as good as mine as to why there are 3 menus if they all populate simultaneously). Once you do that, corresponding markers are compared, and you get your scaling factor.

Also, it seems to me that if you enable "coordinate data for static pose", you must go to the third tab (Static Pose Weights) and disable any markers that do not exist in both of your models (they'll stand out since enabled markers that don't exist are highlighted and say "From File -- NOT FOUND!"). Otherwise, you either can't run the tool, or when you do, it will hang up and never actually finish.

I hope this helps - I know it was a task for me to determine all of this myself, so hopefully this will make your journey a little bit easier. Again, though, I'm far from an expert and this is just me relaying my experience with OpenSim thus far. I'll be happy to help clarify anything I've said here, and hopefully Jim can confirm that what I have been doing is a correct understanding of the process.

Good luck!

Thank you very much.