Adding CustomJoint caused the software to crash.

[collin-kkk]

I am attempting to couple the exoskeleton model with the human musculoskeletal model and add CustomJoint (pelvis -> EXO's Hip), but the software keeps crashing. How should I solve this problem? Additionally, I would like to ask for the usage instructions regarding CustomJoint.

[collin-kkk]

@adamkewley

[collin-kkk]

@adamkewley

[adamkewley]

@collin-kkk , I understand it's frustrating to have a problem with software, but you must learn that repeatably pinging/emoting a random open-source developer on the internet like they owe you money because they didn't to your technical support request within less than a day is going to get you in trouble.

I am providing support only because because I like making open-source software products, there's philanthropic/grant money around to do so, and supporting users is a good way to identify bugs or missing features. However, you are entitled to nothing. Given you've contributed nothing, it is no major loss for me to tell you to look for technical support elsewhere.

To answer your question directly, if only so that other participants have some string to follow:

• I don't have your model and don't know exactly what you're doing with it so, obviously, I cannot reproduce your issue.
• The official documentation for CustomJoint is here: https://simtk.org/api_docs/opensim/api_docs/classOpenSim_1_1CustomJoint.html
• The official documentation for CustomJoint can be difficult to follow. I'd recommend instead going through existing models that contain CustomJoints to see how they're put together. E.g. Arm26.osim contains two, Rajagopal2015.osim contains many CustomJoints.
• OSC doesn't have comprehensive tooling for CustomJoints, because it requires implementing support for visual OpenSim::Function editing (hard). I would recommend editing the .osim file in a text editor (e.g. Visual Studio Code) and using OSC as an external visualizer (it can auto-reload the file on-save in vscode).
• If I were guessing what your issue is:
  • OSC is probably crashing because of an underlying bug in how OpenSim handles kinematic cycles in models.
  • There are known bugs in OpenSim where it will segfault if given unusual joint topologies, such as an Exo attached to ground being attached to a pelvis that's also attached to ground.
  • OSC has downstream tests for these cases (e.g.). Even figuring that out required some development time and investigations (e.g. Investigate bug report from D. K. Smith #773).
  • The only way to fix bugs of this type is to go into opensim-core and deeply investigate why. I haven't had time to do so because I have hundreds of issues, features, upcoming projects that I'm expected to manage, in addition to marketing, support, documentation, etc.
  • As with all open-source software development, you have the freedom to figure these problems out for yourself and contribute to projects like opensim-core.

EDIT: Removed the drive-by animal cruelty suggestion. Hugely unprofessional of me. Note: it is still unprofessional for non-contributing users to expect around-the-clock SLA-style technical support from an open-source developer.