zeros for coordinates.mot from C3D Extract Toolkit

[Saiyi Li]

Hi All,

My problem is that when I convert a C3D file to mot file, the coordinates.mot file can be created. However, when I look the content in it, I found that only a part of ground_force have values, while other columns, such as pelvis_tx, are all 0. Therefore, the model did not move with this mot file. Can any one give some advices?

The following is how I use C3D files:

In the first time, I got an error in line 308 in getKinects.m

frm = C3Dkey.event.Aframes0(C3Dkey.sequence.eventIndex(i,1)) - smoothAll.startPriorViconFrames*C3Dkey.r : ...
C3Dkey.event.Aframes0(end);

because there is no C3Dkey.sequence.eventIndex.

I skip this problem by setting smoothAll.on = 1;

After that all the process can be done and I can see the plots in Matlab without any error. However, when I mount the coordinates.mot file to a model in opensim, the skeleton does not work. I found the problem stated above when I check the coordinates.mot file.

I generated the coordinates.mot files for the examples, but got the same problem, which let to the result that the model did not work. I checked the mot files given by model Gait2354 (subject01_walk1_ik.mot), there are values for all the columns. I assume this is the reason that the model did not work with the mot file generated by C3D Extract Toolkit.

Thank you

Ben

[jimmy d]

Hi Ben,

Im unfamiliar with the toolbox you are using. Could you please give us more details on which toolbox you are using? Most c3d extraction toolboxes will output the markers (.trc) and forces (.mot) collected from a motion analysis trial. With a model, these can be used to run Inverse Kinematics, which will give you the coordinate changes you are looking for.

The following is a list of extraction toolbox's, one of which may be better suited for you data; http://simtk-confluence.stanford.edu:80 ... otion+Data

Hope that helps,
-james

[Saiyi Li]

Hi James,

Thank you for your reply. I am using the C3D Extract Toolkit downloaded from https://simtk.org/home/c3dtoolbox.

I will try to find one in the link you gave to me.

Regards,

Ben