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Biped Crowds 1173
on your hard disk. For information on installing
tutorials, see t he Installation Guide.
This is a fairly simple network of possible motions,
because the characters can only start, stop, tur n
at 90 deg ree angles left and ri g ht (walk_L90 and
walk_R90), and do an about-face (walk_180).
However , for more natural crowd interaction, it’s
advisable to expand the motion flow network
toincludeshorter,morefinelytunedvariations
such as turning at 45 degree increments, moving
in different directions while facing the same way,
loitering motions, and moving at different speeds.
The Biped Motion Library has a comprehensive
list of clips for you to experiment with.
Tip: You can create mot ion clips that c urve
slightlytotheleftandrightbyapplyingBiped’s
footstep-bending operation to straight-line
motionclips.Iftheclipsaremotioncaptured,you
should employ footstep extraction during import
in preparation for the bending operation. Adding
clips that turn slig htly will let the biped crowd
simulation make minute corrections in heading in
order to achieve goal locations more precisely.
Motion flow graphs that work best incorporate
fine-tuned transitions. A good way to check your
motion-flow transitions is by building test scripts
as you build the graph: Add clips to the graph,
add the necessary transitions, and optimize the
transitions. Opt imizing transitions works well as a
starting point and, more often than not, produces
the smoothest transitions. Next, make a new script
that uses your t ransitions, and use the scr ipt to
tweak the motion flow until the feet don’t slide.
The Shared Motion Flow Networks feature lets
many bipeds use a single motion-flow network.
Therefore, it’s practical to make motion-flow
networks large without taxing your computer’s
memory.
Delegat e-Directed B eha vi ora l Goa ls
You can give a biped a behavioral goal by
associating it with a delegate in the Crowd system,
and then assigning behaviors to the delegate.
For example, in the walk ers.max sample, the
behavioralgoalsofeachofthebiped’sdelegates
are to:
• Move toward the sphere using the Seek
behav ior.
• Avoid hitting each other using the Avoid
behav ior.
During a biped crowd simulation, the software
attempts to compute the best motion flow script
for each biped member of the crowd that satisfies
the behavioral goals of its associated delegate. In
other words:
• Thebiped’scrowddelegatedefinesthe
behav ioral goals of the biped.
• The possible motions to reach those goals are
defined by the biped’s motion flow ne twork.
• The Crowd object’s Solve operation computes
the script, or path through the mot ion flow
network,thatbestmeetsthegoalsofthebiped’s
delega te.
So in the walkers.max sample, the simulation will
always choose the b est available walking clip in the
network t hat directs the biped’s delegate toward
the sphere. Each biped’s script evolves as the
crowd "Solve" computes. This is s omewhat like a
real-time "game engine" in that the crowd solver’s