8

Speed Operator 155
Animation Offset Keying group
If you animate the Scale Factor or the Scale
Variation settings or b oth, the software can beg in
applying this animation to all particles as of the
start frame of the animation or the first frame of
the cur rent event, or to each p art icle based on its
age. For instance, if you set Sync By to Particle
Age, and set Scale Factor keys at frames 0 and 30,
then the software will animate the scaling factor
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 already reached its 30t h frame
of existence before reaching the event will enter
the event fully scaled. That is, the software will
apply the Scale Factor value that you set at f rame
30 to each particle aged 30 or above at the moment
it enters the scaling event. However, any particle
that leaves the scaling event b efore reaching age
30 will stop scaling as of its exit frame. In other
words, with respect to particles in other events,
animation of ac tion p ar ameters is retroactive, but
not post-active.
Alternatively, if you set Sync By to A bsolute Time,
the scaling is animated from frame 0 to frame 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 time
that it enters the event.
Note: With the Overwrite Once and Inherit Once
scaling types, scaling always occurs with 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 Sca le Variation
when using O verw rite Once or Inherit Once, it
doesn’t cause scaling animation in the particles,
but rather applies one-time scaling to particles
born during that period. For instance, if you
animate Scale Factor on al l three axes from 100%
to 200% over frames 0 to 30, part icles b orn at
frame 0 are normal size, particles 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 p arameters are
applied at the actual f rames for w hich they’re
set.
•
Particle Age—Any keys set for par ameters are
applied at the corresponding frames of each
particle’s existence.
•
Event D ura tion—Any keys set for parameters
are applied to each particle starting when it first
enters the event.
Uniqueness group
The Uniquene ss setting affects the randomization
of scale variation.
Seed—Specifies a randomization value.
New—Calculates a new seed using a randomization
formula.
Speed
Particle View (page 2–121) > Click Speed in an event or
add a Speed operator to the particle system and then
select it.
This is the default Speed operator, which appears
in the first event when you create a new Part icle
Flow icon. It provides basic controls over particle
speed and direct ion.
Directional controls provided by the Speed
operator are based on the position and orientation
oftheParticleFlowicon. Forbestresultswhen
usingotherobjectsasemitters,usethe
Speed By
Surface Operator (page 2–163)
operator instead.