8

Scale Test 223
Chan g in g —
Defines that the orientation-type
operatorsetsachangingrotationforaparticle.
At each frame t he desirable final rotation may be
different.
For example, if you use the test with a Rotation
operator set to Speed Space Follow, the test will
adjusttheparticlerotationconstantlytoaimatthe
changing final rotation.
Target Rotation Spin group
Defines the angular velocity for each particle when
it reaches the target orientation.
Match Initia l Spin—Sets the angular velocity at the
end of the transition period to the same as the
angular velocity w hen particle enters the event.
Note: The axis of rotat ion might still b e different,
because it is calculated on the fly to let the p art icle
come to the target orientation.
Spin Rate—Defines each particle’s ang ular velocity,
in degrees per second, when it reaches the target
orientation. Available only when Match Initial
Spin is off. Default=0.0.
For a smooth transition to the target orientation,
set to 0.0.
Variation—Definesarandomvariationinthe
SpinRatevaluewhenaparticlereachesthetarget
orientation. Default=0.0.
To obtain the final angular velocity for each
particle, the system multiplies the Variation va lue
by a random number between -1.0 and 1. 0, and
then adds the result to the Spin Rate value. For
example, if Spin Rate=6.0 and Variation=1.0, then
the final angular velocity for each particle would
be between 5.0 and 7.0 degrees per second.
Ease In % —Defines a curve in achieving the final
spin rate. Default=0.0
When set to 0.0, the test produces a linear
interpolation between the initial and final spin
rate, and w hen set to 100.0, the final spin rate is
achieved earlier. For the smoothest approach to
the target orientation, set Spin Rate and Variation
to 0.0, and Ease In to 100.0.
Transition End group
Stop Spinning—When on, halts particle rotation
when it reaches the target or ientation. Default=on.
Even with Spin Rate spinner set to 0.0, we
recommend that you keep this check bo x
on to avoid slow spinning at the end, due to
computational averaging and marginal errors.
Uniqueness group
The Uniqueness setting enables r andomization of
the Variation options.
Seed—Specifies a randomization value.
New—Calculates a new seed using a randomization
formula.
Scale Test
Particle View (page 2–121) > Click Scale Test in an event
or a dd Scale Test to the particle system and then selec t it.
Scale Test lets the particle system check par ticle
scaling, or particle size before or after scaling, and
branch accordingly. The test provides a variety of
axis options for measuring scale or size.
You can use this test to cause a change in behavior
based on size. F or example, a bubble could grow
to a certain size, and then pop. Or an object could
shrink in size unti l it falls under the influence of
a force, like wind.