How do I open a model that contains a custom plugin-dependent component?

[adamkewley]

AK: this question was ported from an email chain. It has been edited, redacted, etc. to fit the discussions format

I want to work on this OpenSim model in OpenSim Creator:

• https://simtk.org/projects/kuo-head-neck

But when I want to open the .osim file, I face an error (screenshot below). What's the problem?

[adamkewley]

The error comes from the OpenSim API whenever it tries to load an .osim file that contains an XML element that it isn't aware of. Your .osim file contains something like:

<DynamicLigamentForce ...>
    <stuff />
</DynamicLigamentForce>

Where DynamicLigamentForce is a component that was added via an OpenSim plugin. In this specific case, the model being loaded is an OpenSim3 model that depends on a "Ligament Model Source" (linked in the SimTK source) that builds a DLL plugin that adds support for DynamicLigamentForce. The plugin dll was probably compiled against OpenSim3 when the authors originally published their work.

OpenSim Creator doesn't support loading custom plugins. Even if it did, that particular project would need to be recompiled against OpenSim 4.x, which may require code changes, upgrades, etc. It's usually straightforward, but really requires a developer to do it: the C++ code can sometimes be tricky to port, or require build systems, IDEs etc. to be set up correctly in order for everything to go smoothly.

If you want to open this specific file then you need to:

• Get OpenSim 3.3 from SimTK: https://simtk.org/frs/?group_id=91
  • Right below "ADDITIONAL PAPERS" there's a little "Previous Releases" dropdown. You want "OpenSim 3.3".
• Install OpenSim 3.3 to C:\OpenSim 3.3 (or wherever you prefer)
• Unzip your neck model thing somewhere (e.g. for me: C:\Users\adamk\Downloads\OpenSim Model\OpenSim Model)
• Copy the .dll into the "plugins" directory of OpenSim (e.g. copy C:\Users\adamk\Downloads\OpenSim Model\OpenSim Model\osimDynamicLigamentPlugin.dll to C:\C:\OpenSim 3.3\plugins)
• Open OpenSim 3.3 (the executable is C:\OpenSim 3.3\bin\opensim64.exe)
• Sanity-check the plugin is installed by going to Tools (main menu) -> User Plugins -> osimDynamicLigamentPlugin.dll
• (you can also set the plugin to "always load when OpenSim loads" during step 5
• Load the model file in OpenSim 3.3 (e.g. C:\Users\adamk\Downloads\OpenSim Model\OpenSim Model\Head_Neck_Model.osim)
• The log panel shouldn't complain about things being missing etc.
• The new ligament forces are editable in the Navigator panel under Forces/Other Forces