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158 Chapter 11: Space Warps and Particle Systems
should be specified with a previous Scale operator,
the Sca le setting in the Shape operator (page
2–176),oraShape Instance operator (page 2–178).
For instance, if you previously used Scale with
OverwriteOncetoscaleparticles’birthsizewithin
a range, and then want to scale them to half their
previous size, use Inherit Once and set Scale Factor
to 50%.
Absolute—Sets the scale continuously,whilethe
particle is in the event, as an absolute percentage
value, disregarding any previous scaling.
UseAbsoluteifyouwanttoanimatetheparticles’
scale explicitly.
Relative First—Sets the scale continuously,whilethe
particle is in the event, as a percentage of existing
scaling. The existing scaling should be specified
with a previous Scale operator, or a Shape Instance.
UseRelativeFirstwhenyouwanttoscalethe
particlesrelativetothescalingatwhichtheyenter
theevent,andoptionallyanimatethescaling,or
before a Relative Successive operator.
Relative Successive—Scales the part icles
continuously, relative to scaling set earlier in the
same event.
Note: Always precede Relative Successive in the
same event with an operator that modifies the scale
channel all the time, such as a Scale operator set
to Absolute or Relative First, or a Shape Instance
operator with t he Sca le check box turned on (it’s
on by default).
Scale Factor group
The operator performs scaling on each particle’s
local axes. It can scale particles on a single axis or
on an y combination of axes.
X/Y /Z—Sets the scaling as a percentage of the
particle’s current size. To scale uniformly, turn on
Constrain Proportions, and then change any axis
setting. Range=0 to 10000000. Default=100.
Constra in Propor ti ons—When on, retains the
current ratio of scale f actor settings, s o that
changing any axis setting changes all of them .
Default=on.
Scale Variation group
X/Y /Z—Sets the sca ling variation as a p ercentage
of the particle’s previous size. To scale uniformly,
turn on Constrain Proportions, and then change
any axis setting. Range=0 to 100. Default=0.
Constra in Propor ti ons—When on, retains the
current ratio of scale variation settings, so that
changing any axis setting changes all of them .
Default=on.
Bias—Lets you choose how to distribute the scaling
variation within the specified range or ranges.
Default=None.
•
None—No bias; scaling variation is distributed
equally through the range.
•
Centered—Scaling variation is concentrated
near the middle of the range; that is, at 0.0%.
With this choice, scaling will occur more
frequently with low percentage values than
w ith ones near the values you set. In other
words, most scaling variants will be close to the
specified scaling value.
•
Towards M inimum—Scaling variation is
concen trated near the lower end of the range
(base-variation); that is, most scaling variants
will be smaller than the scaling value.
•
Towards Maximum—Scaling variation is
concen trated near the upper end of the range
(base+variation); that is, most scaling var iants
will be larger than the scaling value.
Animation Offset Keying group
If you animate the Scale Factor or the Scale
Variation settings or both, the software can begin
applying this animation to all particles as of the
start frame of the animation or the first frame of