Driving Motion with Vicon

I was looking at Sunwook’s sway model that is driven by Vicon, and I
am trying to do the same, however I have a question regarding the
Initial Conditions data. I know how to get the sRel values from Vicon
(the relative position vectors) from the motion capture data, however
I am unsure how to get the r (position vector of the origin) and Axes
(rotational transformation matrix) information from Vicon. Sunwook,
where do you find that information for input into your model?

Thank you for your time,