i | The marker whose origin is being measured. |
j | The marker whose origin is the reference point for the displacement calculation. Set j=0 if you want j to default to the global coordinate system while still specifying k. |
k | The marker in whose coordinate system the displacement vector is being expressed. If not specified, k defaults to the global coordinate system. |

is the displacement of marker i with respect to the global origin.
is the displacement of marker j with respect to the global origin.
is the unit vector along the x-axis of marker k.
is the unit vector along the y-axis of marker k.
is the unit vector along the z-axis of marker k.