Modeling and Animating Human Figures - Computer Animation: Algorithms and Techniques - page 294

With opposable thumb Without opposable thumb

FIGURE 9.11
Simplified hands.

complexity, and therefore image quality, can be maintained by using the full-detail hand model but
coordinating the movement of all the joints of the four fingers with one “grasping” parameter
( Figure 9.12 ) , even though this only approximates real grasping action.

9.2.4 Coordinated movement
Adding to the difficulties of modeling and controlling the various parts of the upper limb is the diffi-
culty of inter-joint cooperation in a movement and assigning a specific motion to a particular joint. It is
easy to demonstrate this difficulty. Stretch out your arm to the side and turn the palm of the hand so it is
first facing up; then rotate the hand so it is facing down and try to continue rotating it all the way around
so that the palm faces up again. Try to do this motion by involving first only the hand/wrist/forearm and

0 10 20 30 80

FIGURE 9.12
Finger flexion controlled by single parameter; the increase in joint angle (degrees) per joint is shown.