Can I load an existing OpenSim model in OSC with *both* a motion file *and* a muscle activations file?

[adamkewley]

AK: this was asked in a linkedin discussion

For the motions file, there's a Load Motion option in the file menu, or the Preview Experimental Data workflow (explained in tutorial 7) has an option to load a model's trajectory/states. The way those currently work is that they load the provided (sto/mot) file into a new state trajectory, followed by using the trajectory to render the model. With that in mind, I don't think that it's currently possible to layer additional state variable data (e.g. muscle activations) from a separate file "over" the existing motions (it would just try to load a new, separate, trajectory).

Related: #857

Note: OSC may resample the states, because the way it loads states (as a complete trajectory, including cache variables) uses more memory than how (e.g.) OpenSim GUI loads states (one at a time, on-demand based on where you scrub the timeline). The reason for this difference is because OSC must be capable of plotting the entire trajectory on-screen as it's (potentially) updated by a simulation thread.

I could look into adding something like this feature, but I'd need an example file/project. Maybe opensim-models already has a suitable example (https://github.com/opensim-org/opensim-models)? Or OpenSim GUI already has a way of merging the states into one file that OSC could load? If users want this feature then they can open a feature request issue.