Modeling and Animating Human Figures - Computer Animation: Algorithms and Techniques - page 301

FIGURE 9.19
Path of the pelvic center from above (transverse plane), exaggerated for illustrative purposes.

Start of stance Midstance End of stance

FIGURE 9.20
Pelvic list to reduce the amount of lift (coronal plane).

Knee flexion
As shown in Figure 9.20 , in a pelvic list with one-piece legs, the swing legwouldpenetrate the floor. Bending
at the knee joint (flexion) allows the swing leg to safely pass over the floor and avoid contact ( Figure 9.21 ) .
Flexion at the knee of the stance leg also produces some leveling out of the pelvic arcs produced by the rota-
tion of the pelvis over the point of contact with the floor. In addition, extension just before contact with the
floor followed by flexion of the new stance leg at impact provides a degree of shock absorption.

Ankle and toe joints
The final part of the puzzle to the walking motion is the foot complex, consisting of the ankle, the toes,
and the foot itself. This complex comprises several bones and many DOFs and can be simply modeled
as two hinge joints per foot ( Figure 9.22 ) . The ankle and toe joints serve to further flatten out the rota-
tion of the pelvis above the foot as well as to absorb some shock.

1 2 3

Start of stance Midstance End of stance

FIGURE 9.21
Knee flexion allowing for the swing leg to avoid penetrating the floor, leveling the path of the pelvis over the point of
contact, and providing some shock absorption (sagittal plane).