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878 Chapter 14: character studio
•WhenBalanceFactoris1(thedefaultvalue)
and you rotate the spine forward, both the hips
and head swing out from their original vertical
alignmenttoasimilardegreetocompensate
for the shift in weight. This value is suitable
for times when 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 sw ings
for ward. There is no movement in the hips to
compensate for the shift in body weight. This
settingisgoodforanimatingasittingbiped
who leans forward, to prevent its hips from
shifting backward. It can also work well for
characters with tails; the tail provides weight in
back of the biped, so the hips don’t have to s hift
backward to compensate when the character
bends over.
• When Balance Factor is 2 and you rotate the
spine forward, the head retains its original
vertical alignment while the COM swings
backward. The hips compensate strongly for
the shift in body weight. This sett ing can b e
useful for violent or acrobatic motions.
In order to affect t he animation, the balance fac tor
must be set before you animate the biped. The
balance factor can be animated to give the biped
different reactions to bending motions over the
course of the animation.
The B a lance Factor parameter appears in the Key
Info rollout > Body section.
Procedure
To s et the bala nce factor:
1.
On the Motion panel, turn off Footstep
Mode if it is turned on.
Note: The Key Info rollout is accessible only
when Footst
ep Mode is turned off.
2. Expand the B
ody b ar on the Key Info rollout.
3. Gototheframewhereyouwanttosetthe
Balance Factor.
4. Click Body Horizontal to select this track
(page 3–1023).
5. If no Body Horizontal key exists at the
frame where you want to set the Balance Factor,
create one by clicking Set Key in the Key Info
rollout.
6. Change the Balance Factor par ameter.
There is no need to click S et Key again after
sett ing the Balance Factor parameter.
7. Rotate the biped’s spine.
The biped’s hips and/or head shift position
based on the Balance Factor value.
Adjusting Ver tical Motion
A ballistic gait is any footstep pattern in which
there are periods with no feet on the ground,
causing the biped to become airb orne, or ballistic.
Running and jumping are ballistic gaits, while
walking is not.
WhenBipedDynamicsisturnedoninthe
Dynamics & Adaptation rollout (page 2–980) and
you a ctivate footsteps, the Body Vertical keys that
are automatically generated during a ballistic gait
period will take gravity and landing speed into
account. The p arameters described in this section
affect B o dy Vertical keys created in this manner.
Air bor ne D yna mics
With footsteps, each airborne period always
begins and ends with Body Horizontal and Body
Vertical keys. These keys define the position of the
biped at lift-off and touchdown.
When the biped is airborne and Biped Dynamics
is turned on, the vertical motion is governed by
physically based dynamics. Its airborne trajectory