Hi AnyBody Community,
I would like to understand the function of weight (WeightX= , WeightY= , WeightZ=) in MarkerDriver definition below for mocap-driven analysis.
#ifdef _STRN
// Marker on the Sternum
CreateMarkerDriver STRN (
MarkerPlacement=Trunk.Segments.SternalBodySeg,
PlaceMarkerAt = XiphoidProcess,
ScaleMarkerPosOnOff=OFF,
OptX=ON,OptY=ON,OptZ=OFF,
UseC3DWeightResiduals = OFF,
WeightX=1,WeightY=1,WeightZ=1
) = {
sRelOpt = {0.02, 0, 0};
};
#endif
The reason I am asking is because I have one unreliable marker in my mocap dataset - the sternum marker STRN. This STRN marker is a virtual/recontructed from four other markers during my mocap data processing. The trajectory from this reconstructed marker is not smooth (see below) but it is still being filtered through with 3Hz lowpass. However, I am still unsure and skeptical on the reliability of this marker as a driver for all 700+ trials for my simulation. I am worry that there might be some ‘drifting of the torso’ happening. Thus, I am thinking of reducing the “weight” defined in the CreateMarkerDriver class above to 0.5 (instead of excluding the marker as a driver entirely from the simulation). My questions are:
- Am I understanding the function of the weight for MarkerDriver defined here correctly?
- If what I understand is correct, and I could reduce the reliability of the model on STRN using the weight, what other driver will drive/to take the slack for this DoF? [I noticed that when STRN is excluded entirely from being a driver, CLAV.Driver.WeightPos is equal to = 2]
- Does reducing the weight has any impact at all on Parameter Identification? Or does it only affect dynamic trials?
For context, I use:-
- full body marker set; with STRN, CLAV, C7, T7, L1, L2, L3, L4, and L5 on the torso
- _THORACIC_MODEL_FLEXIBLE_ switched on
- all cervical, thoracic, and lumbar rhythm are set to _SOFT_RHYTHM_ and the SPINE_MARKERS_SINGLE is switched on
- non-linear disc stiffness (thorax and lumbar) is switched on.
Let me know. Thank you 
Kind regards,
Faizal
