9

Cache Operator 197
upper-left corner of the map, and W is useful only
w ith three-dimensional maps, in w hich context
it specifies depth.
Sync B y—Choose the t ime frame for applying
animated parameters. For further information, see
Animation Offset Keying group (page 2–158).
•
Absolute T ime—Any keys set for p ar ameters are
applied at the actual frames for which they’re
set.
•
Particle Age—Any keys set for par ameters are
applied at the corresponding frames of each
particle’s existence.
•
Event Dura tion—Any keys set for parameters
are applied to each particle starting when it first
enters the event.
Channel group
The Channel setting determines whether the
mapping is applied to a map channel or to a vertex
color channel.
Ma p Channel —The mapping is applied to the
specified map channel.
Ver tex Color Channel—The mapping is applied to
the particles’ vertex color channel.
Show M a p I n Vi ewport—The map coloring is v isible
in the viewports.
Additional Operators
Cache Op erat or
Partic le View (page 2–125) > Click Cache in an event or add
a Cache operator to the particle system and then selec t it.
The Cache operator records and stores particle
states to me mory. When it’s in effect, the first time
you play or go to a frame, the particle motion
up to and including the frame is calculated and
recorded in the cache. Thereafter, playing the
frame or any previous f rames uses the data in
the cache, rather t h a n recalculating the particle
action. Thisisparticularlyusefulwithlargeor
complex particle systems, where playback, and
particularly backtracking, are slow because of the
large amount of processing required. With caching
on, the par ticle system needs to be calculated only
once for each frame, and thereafter playback and
movingamongframesissignificantlyfaster.
Tocacheanentireflow,addaCacheoperatorto
the global event. To cache an individual lo ca l
event, add a Cache operator to it.
To determine how best to implement caching in
your particle system, turn on Particle View >
Track Update > Update Progress, and then play t he
animation or go to a frame relatively distant from
thecurrentframe.Observetheparticlediagram,
and watch for events with actions that highlight
longerthanafractionofasecond,oreventswith
more activity than the rest. Any such events could
benefit f rom caching.
Note: UsenomorethanoneCacheoperatorper
event, unless you’re using two: one set up for
viewpor ts, and t he other for rendering. Similarly,
don’t use global and local Cache operators in the
same flow, unless one is set up for viewports, and
the other for rendering.
Tip: When using real-t ime playback, if playback
isn’tfastenough,youcanusetheCacheoperator
to speed it up. For best results, set the View port
integration step to the same value as the real-time
playback speed, and set cache sampling to
Integration Step. For example, if the real-time
playback speed is set to 1/4x, then the Viewport
Integration Step for viewport should be also set
to 1/4 Frame, and the Cache operator Sampling
parameter should be set to Integration step.
Thus, because real-time playback is showing four