8

1016 Chapter 14: Character Studio
4.
If you like, use the settings in the Projection
Vector group to force delegates to move in a
specific direction.
Obsta cle Av oida nce
An important part of crowd b ehavior is avoidance
of obstacles. Think of an obstacle as any thing that
impedesacrowdmember’sprogress.Examples
of obstacles include walls, telephone poles,
and fences, as well as other crowd members.
Encountering such objects can cause avoidance
behavior, which consists of any combination of
slowing down, turning, and stopping.
There are several ways to implement avoidance in
character studio,including:
•The
Avoid behavior (page 2–1063) is one of
the most commonly used behav iors. Use this
behav ior to cause crowd members to avoid
other crowd members, or spherical objects
in the scene. It works by creating a spherical
volume of avoidance around the avoided object,
so it doesn’t accommodate ir regular objects.
The Avoid behavior is unlike any other behavior
in Crowd. After all the other behaviors exer t
their forces on the delegates, Avoid takes o v er
and has the power to turn, slow down, and
even stop a delegate in order to make it avoid
an obstacle.
•Usethe
Wa l l Repel behav ior (page 2–1079)
to cause crowd members to avoid broad, flat
objects such as walls and fences. You c an set
a maximum distance for the repel effect, and
describetherateatwhichtheforceawayfrom
the wall increases as a delegate approaches the
wal l.
Unlike the Avoid behavior, which can stop
or slow down a delegate, Wall Repel simply
exerts a force on the delegate to turn it away
from the wall. It does not guarantee wall
avoidance. You must work with it’s distance
andfalloffparameters,aswellasitsweightin
theAssignmentsandTeamsdialog,tocontrol
its strength.
•Usethe
Repel behavior (page 2–1070) to cause
crowd members to turn away from an object.
It works exactly like Wall Repel except that it
uses a spherical volume r ather than a plane.
You can set a maximum distance for the repel
effect,anddescribetherateatwhichtherepel
forceincreasesasthedelegateapproachesthe
obstacle.
Repel exerts a force on the delegate to turn it
away from the obstacle. It does not guarantee
avoidance. You must work with its Distance
and Falloff parameters, as well as its weight in
the
BehaviorAssignmentsandTeamsdialog
(page 2–1052)
, to control its strength. Repel
can be used instead of the Avoid behavior as a
simple avoidance technique for non-terrestrial
creatures such as fish or birds.
•Usea
Ve c to r F i e l d .Thisisaspecialtypeof
space warp that crowd members can use to
move around irregular objects such as a curved,
concave surface. You can use the Vector Field
space warp in conjunction with the Avoid
behavior to make delegates slow down when
they approach a complex object, and then go
around it. This guar antees that the delegate wil l
notpassthroughtheobstacle’ssurface.
Yo u c a n a l s o u s e t h e Ve c t o r F i e l d s p a c e w a r p
in conjunction with the
Space Warp behavior
(page 2–1073)
.Thissimplyexertsaforceonthe
delegate that mimics the contours of the object.
Itdoesnotassurethatthedelegatewillnotpass
through the surface of the obstacle. You can use
a Vec tor Field w ith both the Space Warp and
Avoid behaviors to combine their effects.
Procedures
To use the Avoid behavior:
1.
Add an A void behavior to the Crowd object.