"Preserve the mass distribution" option
Posted: Tue Apr 08, 2014 6:06 pm
Dear OpenSim Community,
First of all let me spend two words to introduce myself. I'm an Italian Mech Eng and I've just started my PhD in Biomechanics at the University of Melbourne, Australia.
A big part of my work here at UniMelb will be centred on using this great software program that is OpenSim. For this reason I started doing a couple of Tutorials and then I prosecuted studying the excellent online User Guide.
Reading about Scaling, I found the option Preserve mass distribution during scale and I still have this question: is the total mass of the subject preserved in any case?
This question arises because I found, IMHO, a little inconsistency between two parts of the Guide:
http://simtk-confluence.stanford.edu:80 ... ling+Works
There are two different ways the individual segment masses may be adjusted. One approach is to preserve the mass distribution, which ensures that the masses of the subject-specific model segments are in the same proportion as they were in the generic model. This scales the masses using a constant factor independent of the scale factors that were used to scale the individual segment sizes. The alternative approach incorporates the size scale factors, still ensuring the total mass equals the subject mass, but having the mass of the scaled segments reflect their scale in size.
VS
http://simtk-confluence.stanford.edu:80 ... Scale+Tool
When the box for Preserve mass distribution during scale is checked, the total mass of the generic model is scaled so that it equals the mass of the subject while preserving the relative masses of its body segments. So, for example, if in the generic model the mass of the thigh is twice that of the shank, the mass of the thigh in the scaled model will also be twice that of the scaled shank. If this check box is not checked, the segment masses are scaled based solely on the scale factors applied to each body segment, and the total mass of the model will not equal the experimentally-measured mass of the subject.
Any help would be much appreciated.
Regards,
Alessandro Timmi
PS: Do you know how to change the username and the picture in this forum? Because I changed both of them in my SimTK member profile, but this change didn't affect this forum profile.
First of all let me spend two words to introduce myself. I'm an Italian Mech Eng and I've just started my PhD in Biomechanics at the University of Melbourne, Australia.
A big part of my work here at UniMelb will be centred on using this great software program that is OpenSim. For this reason I started doing a couple of Tutorials and then I prosecuted studying the excellent online User Guide.
Reading about Scaling, I found the option Preserve mass distribution during scale and I still have this question: is the total mass of the subject preserved in any case?
This question arises because I found, IMHO, a little inconsistency between two parts of the Guide:
http://simtk-confluence.stanford.edu:80 ... ling+Works
There are two different ways the individual segment masses may be adjusted. One approach is to preserve the mass distribution, which ensures that the masses of the subject-specific model segments are in the same proportion as they were in the generic model. This scales the masses using a constant factor independent of the scale factors that were used to scale the individual segment sizes. The alternative approach incorporates the size scale factors, still ensuring the total mass equals the subject mass, but having the mass of the scaled segments reflect their scale in size.
VS
http://simtk-confluence.stanford.edu:80 ... Scale+Tool
When the box for Preserve mass distribution during scale is checked, the total mass of the generic model is scaled so that it equals the mass of the subject while preserving the relative masses of its body segments. So, for example, if in the generic model the mass of the thigh is twice that of the shank, the mass of the thigh in the scaled model will also be twice that of the scaled shank. If this check box is not checked, the segment masses are scaled based solely on the scale factors applied to each body segment, and the total mass of the model will not equal the experimentally-measured mass of the subject.
Any help would be much appreciated.
Regards,
Alessandro Timmi
PS: Do you know how to change the username and the picture in this forum? Because I changed both of them in my SimTK member profile, but this change didn't affect this forum profile.