simtk.org

Hi all,

I seem to have a huge problem in running the scaling function in OpenSIM 4.0.
I'm using a full-body model from https://simtk.org/projects/arm_swing
and tried scaling the model using the ScaleSet.xml and Scaling.trc both given in the project page.

However, below is what happens when the scaling process is complete.
Is this some type of compatibility issue between version 3.3 and 4.0?
If that's the case, would the scaling process be done normally in OpenSIM 3.3?
Thank you in advance.

Best regards,
In Bae Chung

Hi In,

I recently had a similar issue in using a 3.3 upper limb model in 4.0, in that using it in 4.0 resulted in the vertebrae flipping and travelling upwards instead of the appropriate direction. I actually think this might have to do with the way in which the thorax joints are defined and how the body geometries are accessed. My solution was to re-define the joint types for the thorax (when you load the 3.3 model in 4.0 it will give you tips on which joints to re-define), and then ensure that the geometries associated with the model are in a 'Geometry' folder in the model directory. After doing this my model loaded in with the spine in the correct position.

Hope that makes sense and helps.

Aaron

Thank you for your reply Aaron.
I'm still not sure about re-defining the joint types. When I opened the model there weren't any tips that telling me which joints I have to re-define. Also, the properties tab of the OpenSIM GUI simply say that the joint type is 'CustomJoint' for all joints. Could you tell me how exactly I'm supposed to change the joint types in the OpenSIM GUI?

One other possibility as you mentioned could be the 'geometry' issue. I noticed that after I load the model, the message below shows up on the screen.
I searched if there are any similar issues, and "duplicate names' could possibly be the solution.
https://github.com/opensim-org/opensim-models/pull/58
From the link above, it says that unique names should be assigned to avoid such messages. Does that mean I have to assign a name for each geometrypath in the code for the model?

Hi In,

I made the changes using an XML editor (Notepad+) rather than in the GUI, and they were mostly changing the joint types (from coupled to rotational I think) based on the warnings provided when the model was loaded in to 4.0. If there are no warnings about joint types being provided then perhaps it is an issue on the geometry side of things - if this is the case then the model definitions (i.e. body frames and axes etc.) might be OK and it just looks wrong visually. Does the original model have an associated 'Geometry' folder in it's base directory? And when you scale do you save the scaled model in a different folder? If this is the case then the scaled model might be using the generic (and therefore incorrect) geometry files to display the model.

Aaron