9

Scale Test 227
Chang i ng—
Defines that the orientation-type
operatorsetsachangingrotationforaparticle.
At each frame the 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 Initial Spin—Sets the angular velocit y at the
end of the transition period to the same as the
angular velocity when particle enters the event.
Note: The axis of rotation might still be different,
because it is calculated on the fly to let the par t icle
come to the target orientation.
Spin R ate—Defines each particle’s angular 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 t he Variation value
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 when set to 100.0, the final spin rate is
achieved earlier. For the smoothest approach to
the t arget 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 orientation. Default=on.
Even w ith Spin Rate spinner set to 0.0, we
recommend that you keep this check box
on to avoid slow spinning at the end, due to
computational averaging and marginal errors.
Uniqueness group
The Uniqueness sett ing enables randomization of
the Variation options.
Seed—Specifies a randomization value.
New—Calculates a new seed using a randomization
formula.
Scale Test
Particle View (page 2–125) >ClickScaleTestinaneventor
add Scale Test to the particle system and then select it.
Scale Test lets the particle system check p article
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 behav ior
based on size. For example, a bubble could grow
to a certain size, and then pop. Or an object could
shrink in size until it falls under the influence of
a force, like wind.