Jm. Zhao et Ni. Badler, INVERSE KINEMATICS POSITIONING USING NONLINEAR-PROGRAMMING FOR HIGHLYARTICULATED FIGURES, ACM transactions on graphics, 13(4), 1994, pp. 313-336
Citations number
28
Categorie Soggetti
Computer Sciences, Special Topics","Computer Science Software Graphycs Programming
An articulated figure is often modeled as a set of rigid segments conn
ected with joints. Its configuration can be altered by varying the joi
nt angles. Although it is straightforward to compute figure configurat
ions given joint angles (forward kinematics), it is more difficult to
find the joint angles for a desired configuration (inverse kinematics)
. Since the inverse kinematics problem is of special importance to an
animator wishing to set a figure to a posture satisfying a set of posi
tioning constraints, researchers have proposed several different appro
aches. However, when we try to follow these approaches in an interacti
ve animation system where the object on which to operate is as highly
articulated as a realistic human figure, they fail in either generalit
y or performance. So, we approach this problem through nonlinear progr
amming techniques. It has been successfully used since 1988 in the spa
tial constraint system within Jack(R), a human figure simulation syste
m developed at the University of Pennsylvania, and proves to be satisf
actorily efficient, controllable, and robust. A spatial constraint in
our system involves two parts: one constraint on the figure, the end-e
ffector, and one on the spatial environment, the goat. These two parts
are dealt with separately, so that we can achieve a neat modular impl
ementation. Constraints can be added one at a time with appropriate we
ights designating the importance of this constraint relative to the ot
hers and are always solved as a group. If physical limits prevent sati
sfaction of all the constraints, the system stops with the (possibly l
ocal) optimal solution for the given weights. Also, the rigidity of ea
ch joint angle can be controlled, which is useful for redundant degree
s of freedom.