Accurately measuring human movement using articulated ICP with soft-joint constraints and a repository of articulated models

A novel approach for accurate markerless motion capture combining a precise tracking algorithm with a database of articulated models is presented. The tracking approach employs an articulated iterative closest point algorithm with soft-joint constraints for tracking body segments in visual hull sequences. The database of articulated models is derived from a combination of human shapes and anthropometric data, contains a large variety of models and closely mimics variations found in the human population. The database provides articulated models that closely match the outer appearance of the visual hulls, e.g. matches overall height and volume. This information is paired with a kinematic chain enhanced through anthropometric regression equations. Deviations in the kinematic chain from true joint center locations are compensated by the soft-joint constraints approach. As a result accurate and a more anatomical correct outcome is obtained suitable for biomechanical and clinical applications. Joint kinematics obtained using this approach closely matched joint kinematics obtained from a marker based motion capture system.