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222 Chapter 11: Space Warps and Particle Systems
Inter face
The user interface appears in the parameters panel,
ontherightsideoftheParticleViewdialog.
Test True When group
Transit ion Peri od E nds—When on, the particles test
True at the end of the specified transition perio d,
andbecomeeligibleforredirectiontothenext
event. When off, particles will not go to the next
event, even if wired. Turn off to disable the test
aspect of Go To Rotation. Default=on.
Transition By group
Determines how the software applies the specified
timing, defined by the Time and Variation values.
Default=Event Duration.
Thepossibleoptionsare:
Absolute Time—Time refers to the overall time
of the system. E ach part icle w ill reach its target
orientation at the frame number specified by
Time.
Par ticle Age—Timereferstothetimeelapsed
since the birth of t he par ticle. Each particle will
reach its target orientation when its age reaches
the va lue specified by Time.
Event Durat ion—Timereferstothetimeelapsed
since the part icle entered the current event.
Each particle will reach its target orientation
when it has been in the current for the number
of frames specified by Time.
Duration—The number of frames particles should
take to reach the target orientation. Default=30.
Variation—The number of frames by which
Duration can vary randomly. Default=0.
To obtain the actual time to the target orientation
for each particle, the system multiplies the
Var i at i o n v a lue b y a r a n d o m nu m b e r b e t w e e n
-1.0 and 1.0, and t hen adds the result to the
Duration value. For example, if Duration=60 and
Var iation=20, then the time to target orientation
for each particle would b e between 40 and 80
frames.
Target Rotation group
When you use an orientation-type operator with
Go To Rotat ion, this setting lets you determine
whether the test sets the target orientation on a
one-time or ongoing basis. Default=Constant.
Co nstantDefines that the orientation-typ e
operator sets a constant orientation for a particle.
Forexample,whenusingaRotationoperatorset
to an orientation matrix other than Speed Space
Follow, the Go To Rotation operator would acquire
the target orientation only once, and then use it
as its goal.