8

Shifting the Biped’s Balance 735
• 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 unnaturally
compensates for balance. As each step is taken,
the legs and body move in an awkward fashion,
as if there was an invisible weig ht attached to
the front of the charac ter.
Center of mass moved behind the biped in rubber-band
mode
Center of mass moved in front of the biped in rubber-band
mode
For a tutorial that uses this technique, see
“Creating the Illusion of Weight”.
Balance Factor
The balance fac tor (page 3–1008) 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 ov er.
Results whe n balance fac tor is set to 0.0, 1.0 and 2.0 before
the spine is animated to make the bip ed bend over.
The B a lance Factor parameter can have any value
from 0 to 2:
• When Balance Factor is 1 (the default value)
and you rotate the spine forward, both the hips
and head swing out from their original vertical
alignment to a similar degree to compensate
for the shift in weight. This value is suitable
for times w hen the biped leans forward while
standing.
• When Balance Factor is 0 and you rotate the
spine forward, the COM keeps its original
vertical alignment, and the head swings
for ward. There is no movement in the hips to
compensate for the shift in body weight. This
setting is good for animating a sitting bipe d
who leans forward, to prevent its hips from
shifting backward. It can also work well for
characters w ith tails; the t ail provides weight in
backofthebiped,sothehipsdon’thavetoshift