# Pelvis Angle Converter

Pelvis Converter PlugIn needs Vicon PlugIn Gait - or at least the pelvis
progression angles generated by PlugIn Gait in the trials you want to
process.

Settings Dialog

### What it Does

The Pelvis Converter PlugIn converts the pelvis progression angles
generated by Vicon PlugIn Gait from a YXZ floating-axis Euler angle, to a ZXY
floating-axis Euler angle. It does this by re-composing the Euler angle from
PlugInGait into a 3 x 3 rotation matrix, then decomposing the matrix again,
but in the required rotation order.

The results are saved in two "angle" trajectories in the trial. The names
of the two trajectories used (left and right versions are generated) can be
specified in the settings dialog.
The default names used are LNewPelvisAngles and RNewPelvisAngles. These names
have been added to the accompanying ConvPelvPiG.mkr file (a modified version
of PlugInGait.mkr) which may help when analysing your results in other
software such as Vicon Polygon. Please refer to your Vicon documentation
about how to use this new file.

### Why ?

First of all, there's nothing wrong with PlugInGait. It's just that the
Euler angle representation it uses is not so clinically intuitive as that
suggested by Richard Baker (and others). The fact that the Pelvis Converter
is able to perform the conversion using the PlugIn Gait Euler angles, proves
that in fact, this gives a perfectly valid representation of the orientation
of the pelvis.

Pelvis Converter uses the PlugIn Gait angles, rather than calculating them
directly from the marker data, because the progression frame calculation in
PlugIn Gait is a relatively complicated algorithm. This appoach guarantees
that the two calculated pelvis Euler angle triplets will always agree, even
if things change in PlugIn Gait in the future.

### It's not working !

If the two new angle trajectories do not appear as you expect, then please
check the Workstation Processing log (in the View menu) to get feedback
from the PlugIn.