9

Shifting the Biped’s Balance 877
characters, the physical center of mass is located
near the pelvis.
Typical placements for the center of mass are:
• Characters that stand erect, such as humanoids,
use the default lo cation of the center of mass
within the pelvis.
• Characters that naturally lean forward, such
as some dinosaurs and birds, should have the
center of mass mo ved slightly forward of the
pelvis.Thisisalsogoodforrobotsanddroid
soldiers.
• Characters that are holding a heavy weight out
in front of them, or overweight characters,
might need their center of mass moved slightly
forward of the pelvis.
• Characters that are pushing or pulling objects
might need their center of mass moved slightly
behind the pelvis.
Note: Ifyouplacethecenterofmasstoofarin
front of the pelvis, the character u nnatura lly
compensates for balance. As each step is taken,
the legs and b ody move in an awkward fashion,
as if there was an invisible weight attached to
the f ront of the character.
Center of mass moved b ehind the biped in rubber-band mo de
Center of mass moved in fron t of the biped in rubber-band
mode
For a tutorial that uses this technique, see
“Creating the Illusion of Weight”.
Balance Factor
The balance factor (page 3–914) is an animatable
parameter that determines how the biped’s hips
and spine will compensate when the biped bends
for ward or backward.
Thebalancefactordeterminesthedegreeand
directioninwhichtheheadand/orhipsswingout
from their original vertical alignments when the
biped bends over.
Results when balance factor is set to 0.0, 1.0 and 2.0 before the
spineisanimatedtomakethebipedbendover.
The Ba lance Factor parameter can have any value
from 0 to 2: