trvec = tform2trvec(tform) extracts
the Cartesian representation of translation vector, trvec ,
from a homogeneous transformation, tform. The
rotational components of tform are ignored. The
input homogeneous transformation must be in the premultiply form for
transformations.
Homogeneous transformation, specified by a 4-by-4-by-n matrix
of n homogeneous transformations. The input homogeneous
transformation must be in the premultiply form for transformations.