9

Speed Operator 159
the cur rent event, or to each p article based on its
age. For instance, if you set Sync By to Particle
Age, and set Scale Factor keys at f rames 0 and 30,
then the software will animate the scaling fac tor
for each particle between its birth and its 30th
frame of existence, if the particle is in the scaling
eventorapriorevent.Followingthisexample,any
particle that has a lready reached its 30th fra me
of existence before reaching the event will enter
the event fully scaled. That is, the software w ill
apply the Scale Factor value that you set at frame
30 to each p article aged 30 or above at the moment
it enters the scaling event. However, any particle
that leaves the scaling event before reaching age
30 will stop scaling as of its exit fr ame. In other
words, with respect to particles in other events,
animation of action parameters is retroactive, but
not post-active.
Alternatively, if you set Sync By to Absolute Time,
the scaling is animated from frame 0 to fr ame 30
of the animation, regardless of particle age, and
even if no particles are in the event at that time. Or,
if you set Sync By to Event Duration, the scaling
animation is applied to each particle as of the t ime
that it enters the event.
Note: With the Over write Once and Inherit Once
scaling types, scaling always occurs w ith respect
totheentireanimation;thatis,inAbsoluteTime
mode. Thus, when either of those scaling types is
in effect , the Sync By setting is unavailable. Also,
if you animate Scale Factor or S ca le Variation
when using Over write Once or Inherit Once, it
doesn’t cause scaling animation in the particles,
but r ather applies one-time scaling to particles
born during that period. For instance, if you
animate Scale Factor on all three axes from 100%
to 200% over frames 0 to 30, particles born at
frame 0 are normal size, par ticles born at frame
15 are one-and-one-half times normal size, and
particles born at frame 30 (and thereafter) are
twice normal size.
Sync B y —Choose the time frame for applying
animated parameters:
•
Absolute T ime—Any keys set for parameters are
applied at the actual frames for which they’re
set.
•
Particle Age—Any keys set for par ameters are
applied at the corresponding frames of each
particle’s existence.
•
Event Dur at ion—Any keys set for parameters
are applied to each particle starting when it first
enters the event.
Uniqueness group
The Uniqueness setting affects the randomization
of scale variation.
Seed—Specifies a randomization value.
New—Calculates a new seed using a randomization
formula.
Speed
S peed O per at or
Particle View (page 2–125) > Click Speed in an event or add
a Speed operator to the par ti cle system and then select it.
This is the default Speed operator, which appears
in the first event w hen you create a new Particle
Flow icon. It provides basic controls over particle
speed and direction.
Directional controls provided by the Speed
operator are based on the position and orientation
oftheParticleFlowicon. Forbestresultswhen
usingotherobjectsasemitters,usetheSpeed By
Surface Operator (page 2–167) operator instead.