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218 Chapter 11: Space Warps and Particle Systems
value. For example, if Time=60 and Variation=20,
then the time to target for each particle would be
between 40 and 80 frames.
Subframe Sampling—Turningthisonhelpsavoid
particle "puffing" by timing particles at a much
higher subframe resolution (that is, t hroughout
each fr ame), rather than using the relatively coarse
frame resolution. Default=on.
"Puffing" is the effect of clustering particles, rather
than producing a continuous stream. This effect is
especially noticeable when the emitter is animated.
Use D ock i ng S peed—Lets you specify part icles’
speed when they reach t he target.
A part icle might be required to reach the target
from a specific direction at a specific speed. When
UseDockingSpeedisoff,thesoftwarecalculates
apathforparticlestoreachthetargetinthe
shortest distance w ith the least acceleration along
the p ath. When Use D ocking Speed is on, the
software ca lculates p articles’ final speed when they
reach the target using the Speed and Variation
parameters. Therefore if you want a “smooth
landing,” set Speed to 0.0. Default=off.
Speed—The speed of particles when they reach the
target in scene units per second. Default=100.0.
Variation—TheamountbywhichtheactualSpeed
value can vary randomly. Default=0.0.
Target group
By default, Find Target uses its ow n target icon,
but you can use these con trols to designate other
scene objects as targets instead.
Icon—Use the Find Target icon as the target.
Each Find Target test has its own target icon. Even
if you don’ t use it as a target, it still influences
particle behavior if you set the docking type to
Parallel,Spherical,orCylindrical.
Mesh Objects—Useoneormorescenemesh
objects as targets. Choose this to make the list and
list-management buttons available.
If you designate more than one target, the target
used by each particle is determined by the choice
in the
Object drop-down list in this group.
[list]—Showsthemeshobjectsusedastargets.If
more than three target objects apply, a scroll bar
appears a t the right side of the list.
Add—Click this button, and then select a mesh
object in the scene to add it to the list as a target.
By List—Click this button, and then use the Select
Target Objects dialog to add one or more mesh
objects to the list. The objects must already exist
in the scene, and the dialog shows only eligible
objects.
Remove—To remove a target object from the list,
first highlight it and then click this button. Any
removed objects remain in the scene.
Sync B y—Choosethetimeframetousewhen
sending part icles toward animated objects
when using Animated Shape or Follow Target
Animation:
•
Absolute T ime—Animation derived from the
target is applied to particles immediately.
•
Par ticle Age—Animation derived from
thetargetisappliedtoparticlesatthe
corresponding frames of each particle’s
existence.
•
Event Dur ation—Animation derived from the
target is applied to particles is applied to each
particle starting when it first enters the event.
Animated Shape—Tu r n on to allow p ar t icles
to t arget the surface of an object whose form
is animated by scaling, by morphing, or with
modifiers. This requires more computation,
becausethedestinationmustbeupdatedatevery
integration step.