In a virtual environment for small groups of interacting participants,
it is important that the physical motion of each participant be repli
cated by synthetic human forms in real time. Sensors on a user's body
are used to drive an inverse kinematics algorithm. Such iterative algo
rithms for solving the general inverse kinematics problem are too slow
for a real-time interactive environment. In this paper we present ana
lytic, constant-time methods to solve the inverse kinematics problem a
nd drive an avatar figure. Our sensor configuration has only eight sen
sors per participant, so the sensor data is augmented with information
about natural body postures. The algorithm is fast, and the resulting
avatar motion approximates the actions of the participant quite well.
This new analytic solution resolves a problem with an earlier iterati
ve algorithm that had a tendency to position knees and elbows of the a
vatar in awkward and unnatural positions.