9

Non-Biped Crowds 1179
why Backtracking is off by default, but it’s of ten
thebestwaytoresolveproblemswithcolliding
bipeds.
Non-B iped Crowds
Motion synthesis in character studio lets
the software deriv e character motion from a
combinat ion of crowd behaviors and either motion
flow networks, when animating bipeds (see Biped
Crowds (page 2–1172)), or clip controllers, when
working with non-bipedal creatures. In the latter
case, using the Global Motion Clip and Master
Motion Clip controllers, you can animate groups
of creatures such as birds, butterflies, schools of
fish, and insects. You can create clip controllers
either as block controllers in Track View, or, more
directly, with the Crowd helper controls on the
Global Clip Cont rollers rollout.
TwoApproachestoAnimation
You can animate your creature either in place
with looping animation but no transformational
motion (such as a bird flapping its wings), or you
can incorporate transformational motion into the
animation as well (the bird moves upward while
flapping its wings). In-place cyclic motion lends
itself to fly ing or swimming motions like birds
and fish, while adding lateral motion lends itself
to crawling type animation where feet should be
planted on the g round and not sliding. Depending
on which you use, you toggle options on the
Motion Clips tab of the Synthesis dialog. In both
cases, you use crowd delegates dr iven by behaviors
to motivate the creatures, which are linked to those
delegates.
Note: To animate a model for motion synthesis,
apply modifiers to the model and animate their
parameters. Modifiers such as Bend, Taper,
Wave, and Xform produce animation you can use
w ith mot ion synthesis. Do not use sub-object
animation, such as animation of vertices on an
Editable Mesh object.
Cyclic I n-Place Animation
First you create a creature with a few short loop
cycles, like the beating of wings, gliding, turning
left and tur ning r ight. This creature is assig ned as
the Global Object or the master object from which
the motion clips will be derived. Then clones
oftheoriginalcreaturearecreated. Theclones
are positioned and linked to delegates. States are
created to select which clips will play b ased on a
state.
For example, if a bird (delegate) is pitching up or
accelerating, the fast-beating clip is used; if t he
bird (delegate) slows to a stop, the wings-at-rest
clip is used, and so on. D uring synthesis, the
software determines which state should be active
depending on the speed and direction of the
delegates. An act ive state determines w hich clip
should be applied to the clones of the original
object. Clips are blended together to create the
animation. Available sta tes are speed, acceleration,
pitch, pitch velocity, heading velocity, or script
(MAXScript).
Animation with Lateral Motion
For multi-legged c reatures that walk, you can
animate lateral motion as well as the cyclic motion
of the legs moving. This is done to ensu re that
the creatures’ feet do not slide as they move. The
software then uses the lateral motion information
to create a state that perfectly matches the actual
motion. The software then strips the actual
motion out. When a delegate approaches the speed
and heading recorded in that state, the appropriate
motion clip is tr iggere d. This technique minimizes
sliding feet.
Use the character studio crowd tools to create
the initial motion for the delegates. Use a seek or
avoid behavior to steer birds, for example. Your