I want to use AnyBody to compare two motion capture systems. One uses two force plates, while the other does not. I am not sure how the reaction forces for walking are calculated in each case (with and without force plates).
For the analysis, I am implementing the scripts for plug-in-gait-simple Full Body and Full Body GRF Prediction, respectively. Specifically, I am interested in knowing if AnyBody uses the total of frames from the C3D file or just the frames where the foot are touching the force plates, and how does it work in the case of GRF Prediction? What part of the gait cycle is used?
The models will use whatever is specified in the TrialSpecificData.any. It is up to the user to select what part of the C3D file requires analysis. So in case you recorded some movement before the person stepped on the force plates - the readings from the force plates will be at 0, as well as the contact will not be detected, and this quite likely will lead to failure in the inverse dynamics. The GRF version will naturally add predictive elements and find balance throughout the entire range of frames.