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228 Chapter 11: Space Warps and Particle Systems
Inter face
The user interface appears in the parameters panel,
ontherightsideoftheParticleViewdialog.
Ty pe—Choose the type of measurement to test.
Youcantestactualscaling,orthesizebeforeor
after scaling. Default=Scale.
For example, if the X-axis size of a particle ’s
bounding box starts out at 10 system units, and
you then use the Sca le operator to scale it by 150%
ontheXaxis,thepre-scalesizeis10,andthe
post-scale size is 15. And, of course, the scale is
150.
Note: Thesoftwaremeasuresparticlesizebased
on each particle’s bounding-box dimensions in
the particle’s local coordinate space. With the
low-polygon Shape options Tetra and Sphere, the
result of this measurement might not be the same
as the Shape operator’s Size va lue.
•
PreS cale Si ze—Tests the size before scaling.
•
PostS cal e S iz e—Tests t he size after sca ling.
•
Scale—Tests the sc aling percent age.
Axis—Choose the axis to measure.
Default=Average.
•
Aver a ge—Obtains an average measurement
by adding the sizes on all three axes and then
dividing by three.
•
Mi nimum—Uses the smallest dimension.
•
Median—Usesthemiddledimensioninorderof
size.Forexample,iftheparticledimensionsare
X=5, Y=6, Z=12, then the number compared
to Test Value would be 6.
•
Maximum—Uses the largest dimension.
•
X/Y /Z—Uses the specified dimension.
Test True if Par ticle Value—Lets you specify whether
the test p asses part icles on to the next event if
the speed test succeeds or fai ls. Available for all
tests except True When Accelerates/Decelerates.
Default=Is Greater Than Test Value.
By default, Scale Test returns True if the value
tested for exceeds the Test Value quantity, but you
can alternatively choose Is Less Than Test Value.
For example, if you set Ty p e to Sca le and set Test
Va lue=150 and Variation=0, and choose Is Less
Than Test Value, a particle will move to the next
event only when its scaling factor is less than 150%.
Size group
ThesesettingsareavailablewhenTypeissetto
PreScale Size or PostScale Size.
Test Value—Thespecificsizetotestfor.
Default=10.0.
Variation—Theamountbywhichthevaluetested
for can vary randomly. Default=0.0.
To obtain the actual test value for each particle, the
system multiplies the Variation value by a random