On Articulated Motion and Its Recovery

This paper addresses the subspace properties and the recovery of articulated motion. We point out that the nature of the motion subspace of an articulated object is a combination of a number of intersecting rigid motion subspaces. The rank of that motion subspace is less than that of each articulated part combined, depending on the connection between every two linked parts, either a rotation axis or a rotation joint. The reduced dimension(s) results from an intersection between two motion subspaces of the linked parts which is exactly the motion subspace of the axis or joint that connects them. From these observations, we describes the rank constraints of articulated motion, gives an algorithm to recover the image motion of the axis or joint and propose a novel but simple approach to recover articulated shape and motion from a single-view image sequence, which is based on subspace clustering.