9

1212 Chapter 14: character studio
As delegates approach designated objects during
the crowd simulation, they steer clear of them
whileturningand/orbrakingasnecessary.This
behavior uses three different methods to let
delegates avoid each other and other objects: Steer
To Avoid, R ep el, a n d Ve c t or F i e l d .
Steer to Avoid behavior is best used for animals
that steer around each other at close proximity.
Earthbound animals and fish typically do this.
Steering motion ma y be sudden since its action is
often engaged for relatively short periods of time.
By contrast, Repel avoidance behavior mimics the
continuous action of a repellent magnetic field.
Birds, bats and flying insects are best animated
with large Repel fields so that they can smoothly
avoid e ach other while m aintaining a comfortable
margin of error . Repel forces prevent intrusion
from al l sides, regardless of the direction of tr avel.
Thus even animals that rely mainly on Steer
to Avoid will also need some degree of Repel
avoidance to maintain spatial separation when
theyaremovingthroughdensetraffic.Theforces
of Repel avoidance are always directed uniformly
outward in a spherical shape.
Use V ector Field avoidance for cases where
crowd members must avoid hitting the more
complexshapesofarbitrary3dsMaxobjects.The
outward forces of the Vector Field avoidance can
constructed to form the shape of any object. For
example, suppose you want to animate a school
of fish swimming around a sunken ship. In this
case,avectorfieldcanbecreatedsothatitextends
theshapeoftheshipintothesurroundingspace.
The field is computed by scan converting the ship’s
surface normals into a 3D lattice that surrounds
theship.Thesenormalswillextendintospaceas
"beacons" in the 3D lattice, telling the fish how to
best swim away from the shape of the ship. As the
fish enter the space of the vector field lattice, they
can be precisely repelled along an avoidance force
directed away from ship’s surface.
Note: In the explanations that follow, the word
"target" is used to refer to the object or objects to
be avoided.
Interfa ce
None (la bel)—Specifies a single target. Click this
button, and then click the target object in the
viewport. The target name then appears on the
button.
If you’ve selected multiple targets using Multiple
Selection (see next item), the word Multiple
appears on the button. To see which objects are