External Forces transform during RRA

[Quinten Humphrey]

Hello, I was wondering if someone could help explain this to me and why it is happening. I haven't found a post yet describing this.

ExternalForce::ground_force
Data source being set to Sub05_Trial06_VR_Box01_grf - Copy.mot
ExternalForce::1_ground_force
Data source being set to Sub05_Trial06_VR_Box01_grf - Copy.mot

ExternalForce::ground_force_transformedP
Data source being set to Sub05_Trial06_VR_Box01_grf - Copy.mot_transformedP
ExternalForce::1_ground_force_transformedP
Data source being set to Sub05_Trial06_VR_Box01_grf - Copy.mot_transformedP

[John Davis]

I believe this message is just telling you that the external loads configuration file is assigning the file name for the data to each separate ExternalForce in the ExternalLoads list. In an external loads config xml, each ExternalForce object has an xml tag data_source_name, and the ExternalLoads object (which is just a list of ExternalForces) has an xml tag datafile. The comments in the default xml templates say that datafile overrides data_source_name, if datafile is specified.

This allows you to set separate files for separate forces, if you want to - maybe if you had one external force that was sampled at a different frequency than another this would be useful. But I think the usual case would be that all external forces would be in the same file, in which case you can leave data_source_name blank, and just specify datafile. So I think the message is telling you that OpenSim is setting data_source_name for each ExternalForce to be the datasource file in the ExternalLoads object, which is (I'm assuming) exactly what you want to happen.

[Quinten Humphrey]

But when I look at the transformed files, the grf data is completely different than what I am using.

[Sanne Vancleef]

Hi Quinten,

How did you solve this? I have the same issue.

Thank you,
Sanne

[Mohammadreza Rezaie]

Hi,

I had similar issue. OpenSim automatically takes the first line of the MOT file as a name for "Data source". This might be problematic when the name refers to another file path or address (real or imaginary) and in my case, couldn't read the file. You can simply change the first line to something like "GRF" or any file name without extension. If there isn't any problem in reading the file, just ignore the message.

Best,
Mohammadreza