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1026 Chapter 14: Character Studio
Tip:
The inclusion of stopping and loitering
motions in the motion flow network is sometimes
helpful in preventing excessive backtracking
sincestoppingisalwaysaneffectivewaytoavoid
collisions in a tight situation. In general, the more
variation in speed and direction that is possible,
themorequicklythebacktrackingfeaturewillfind
asolution.
In order to m ake the backtracking computationally
manageable, the biped crowd members are
computed one at a time, in order of
priority
(page 2–1087)
. Thus, the crowd interaction is
accumulated with each successive biped added to
the animation. In other words, each waits its turn
to compute its complete animation, which entails
avoiding the bipeds that have been computed
before it. It follows that bipeds with the lowest
priorities generally encounter the most collisions,
since they must steer around all the biped s that
have higher priorities.
Prepar ing Chara cter s for a Biped Crowd
To create a biped crowd simulation, you will need
several bipeds. Because the crowd simulation
factors in each biped’s leg length when applying
clips to the biped, yo ur simulation will be more
accurate if your bipeds are the correct size from
the start.
One str aightforward workflow would be:
• In a separate file, create or acquire a few
character models for your scene.
• Skin the characters with Physique or with
another m ethod, such as the 3ds Max Skin
modifier.
• Clone the characters and change something
abouteachone,suchasthecolorofclothingor
hair, and the character’s height. See
Scaling a
Character (page 2–951)
.
• Giveeachcharacterauniquenamethatwill
allow you to identify it in the simulation to
some degree. Example: BigMan02, LittleGirl03.
See
Naming the Biped (page 2–705) .
• For each character, disable the MeshSmooth
modifier or other modifiers above Physique
that add polygons.
• Hide the character meshes and leave the bipeds
vi sible.
This setup makes it easy to merge the characters
into the crowd scene. When characters are merged,
the meshes themselves will be hidden, w hich wil l
improve system performance.
Prepar ing M otions for a B iped Crowd
The clips you use for a biped c rowd simulation can
be loaded from the CD that comes with character
studio, imported from motion capture files, or
created from scr atch.
The integrity of transitions between clips in the
motion flow network is very important when
creat ing a biped crowd simulat ion. When creating
transitions for a single biped, it’s a simple matter
to correct individual transitions after the motion
flow script has been created. With a crowd,
having to co rrect transitions for each biped after
the simulation is complete would be extremely
time-consuming. Itismuchmoreefficientto
ensure your transitions are correct before star ting
to solve the simulation.
Onewaytomakethisprocesseasieristosetupall
motions so each has an ideal transition of exactly
the same number of frames, such as 10 or 15. Then
you can optimize transitions for this length, and
all or most transitions will work fla wlessly.
To check transitions, create a simple script for one
biped using several transitions in the graph. Check
the motion and work w ith transitions individually
until t hey look right. You mig ht not catch all bad
transitionswiththismethod,butyou’llcatchmost
of them. A “bad” transition would be one where
the feet sk ip or hop when they should be wal king,