Further constraints on visual articulated motions

This paper derives what we term the Euclidean hinge constraint for projective reconstruction of objects displaying articulated motion. A Euclidean hinge is defined here to be an articulation axis with the proviso that any plane perpendicular to the articulation axis in link 1 has a coincident plane which is perpendicular to the articulation ads in link 2 and that these planes remain coincident under articulated motion. This constraint permits the independent projective reconstructions of two adjacent articulated links to be placed in a common frame. The constraint may be expressed mathematically by considering what we define as circular parallax. Additionally the existence of a Euclidean hinge permits the permits the projective frame to be brought nearer to a Euclidean frame for the reconstructed object. A brief reprise of the method of articulation axis estimation is given together with a more extensive series of experimental results.