3D Human Body Modeling

Modeling a human body first implies the adaptation of an articulated 3D
structure, in order to represent the human body biomechanical features. Secondly,
it implies the definition of a mathematical model used to govern the
movements of that articulated structure.
Several 3D articulated representations and mathematical formalisms have been
proposed in the literature to model both the structure and movements of a human
body. An HBM can be represented as a chain of rigid bodies, called links,
interconnected to one another by joints. Links are generally represented by
means of sticks (Barron & Kakadiaris, 2000), polyhedrons (Yamamoto et al.,
1998), generalized cylinders (Cohen, Medioni & Gu, 2001) or superquadrics
(Gavrila & Davis, 1996). A joint interconnects two links by means of rotational
motions about the axes. The number of independent rotation parameters will
define the degrees of freedom (DOF) associated with a given joint. Figure 1
(left) presents an illustration of an articulated model defined by 12 links (sticks)
and ten joints.
In computer vision, where models with only medium precision are required,
articulated structures with less than 30 DOF are generally adequate. For
example, Delamarre & Faugeras (2001) use a model of 22 DOF in a multi-view
tracking system. Gavrila & Davis (1996) also propose the use of a 22-DOF
model without modeling the palm of the hand or the foot and using a rigid headtorso
approximation. The model is defined by three DOFs for the positioning of
the root of the articulated structure, three DOFs for the torso and four DOFs for