A computer model based on superquadrics for the analysis of movement disabilities

The use of motion analysis equipment to study movement disabilities is a major step toward improving treatments of disabled persons. We propose such an approach allowing the analysis of human motion in 3D space without using the tracking of markers. The system we develop is composed of three cameras which acquire synchronized sequences of a human in motion. Then the treatment of our approach is divided into three steps: first, a set of 2D points belonging to the boundaries of the human body in motion are extracted from the three images at each acquisition time. The projection of a human body model is matched with these data. Then, these matchings allow to obtain by reconstruction the configuration of the model in the 3D space at each acquisition time. Finally, some motion parameters can be extracted. The aim of this paper is to describe the human body model that we use and the procedure of matching of its projection. We use an articulated 3D model which consists of a set of non deformable superquadrics. We show that the perspective projection of a class of them can be approximated by a 2D tapered superquadric. Consequently, we propose a fuzzy clustering algorithm adapted to the 2D recognition of the superquadrics.