8

856 Chapter 14: Character Studio
forearms, and upper-arm keys are stored in the
clavicle track. All the spine keys are stored in the
spine 01 track. Although you can see all of these
objects in the Track View hierarchy, they have no
transform track, unless you enable them in the
Separate Tracks group of the
Keyframing Tools
rollout (page 2–816)
.
Forexample,ifyourotateabipedfoot,akeyis
createdinthebipedthightrack.Thisoptimized
approach works well in m any cases. If your
animation requires extensive hand and finger
keyframing,turnonArmsontheKeyframing
Tools rollout; all of the arm transform tracks are
now enabled, down to the first finger link on each
finger. Now if you delete an upper arm key, your
finger-hand animation is preserved.
How D yna mics a nd Footsteps R elate
When footsteps are created, a footstep track
displays in Track View – Dope Sheet. Footsteps
appear as blue and green blocks, laid out to show
their exact placement in time. If you compare
thecenterofmasstrackstothefootsteps,you
will notice that frames where leading and trailing
edgesofthefootstepsoccuralsohavekeysfor
the center of mass Body Vertical and Horizontal
tracks. These keys contain dynamics information
used by character studio to calculate airborne
body position relative to gravity, and leg bend on
landing and balance. Biped Dynamics is the reason
you do not need a vert ical center of mass key at the
top of a jumping motion or at the bottom of dip
when the biped lands from an airborne period .
Click and drag the middle of a footstep to move it
in time. Click and drag one edge of a footstep to
stretch t he footstep in time.
Note: Changing the duration of footsteps or
moving them relative to one another may change
the “support relationships” of the footsteps.
Whenever the support relationships change, Biped
generates new keys and deletes any existing leg
keys in the airborne period b etween the edited
footsteps.
Because of Biped Dynamics, no keys are necessary for the
highest part of this jumping motion or for the dip when the
biped lands; character studio calculates the trajector y of
theBody.Thisimageshowsthecenterofmasstrajectory.
Keyframes are white squares on the tra jectory.
Simply change gravity (GravAccel on the Dynamics &
Adaptation rollout), and the jumping motion is flattened.
Thebipedlookslikeit’shoppingonthemoon.
By selecting half the footsteps in Track View - Dope Sheet
and moving them to the ri ght in time, the bipe d has to jump
higher to account for the added time to the nex t footstep.
Notice that the yellow do ts, representing frames, are tightly
bunched together; there are more frames in this airborne
period.
Here,thecenterofmassismovedintheZplane. Now
the biped heel never hits the ground; the biped appears
to do a jump using just its toes. Here, character studio
understands that you want to override the calculated
trajectory and position the keyframe yourself.