Tips and Tricks

How to get the best results out of AddBiomechanics:

1. Label markers on bony landmarks vs. markers on soft tissue

For best results, markers placed on bony landmarks should be moved much less than markers placed on soft tissue during optimization. AddBiomechanics relies on <fixed>true</fixed> and <fixed>false</fixed> annotations in your *.osim model file to tell the difference between bony landmarks and soft tissue. If you do not provide these annotations, the AddBiomechanics will try to guess, but may not be successful.

2. Make sure your generic model markerset matches the markers in the experimental marker files

If your *.osim file doesn't contain the markers that are used in your marker files, AddBiomechanics won't be able to produce any results.

3. Check your marker files to ensure consistent marker trajectories

"Garbage in, garbage out" applies to AddBiomechanics. The tool will do its best to correct common human error in marker trajectory data (like having a pair of markers trade labels partway through a trial) but for best results try to keep your input data as clean as possible.

4. Exercise the joints as much as possible!

The optimizer relies on movement to optimize the scaling of the model. Upload trials with plenty of joint movement for optimal results.

5. Review the per-trial warnings to see if there's anything fishy about your mocap data

AddBiomechanics will do its best to proactively warn you if it detects something in your uploaded data that will likely lead to a problem.

How to use Custom Markersets

Getting started with using custom skeletons and custom markersets with AddBiomechanics:

Using custom marker sets with AddBiomechanics is easy:

  1. Start by downloading the OpenSim GUI
  2. You'll also want to download a skeleton model to base yours off of: Rajagopal 2015 and Lai Arnold 2017 are popular options.
  3. Then you can use the Marker Editor in OpenSim to add your marker set to your skeleton. Export a *.osim file when you're done.
  4. Now you can use your new *.osim file as your Custom OpenSim Skeleton and Markerset in AddBiomechanics!