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198 Chapter 11: Space Warps and Particle Systems
times as many frames per second, and the Cache
operator has stored four times as many frames per
second, the two are synchronized. If t he real-time
playback speed is set to 2x or 4x, set the Viewport
Integration Step to Frame.
Procedure
Example: TousetheCacheoperator:
1.
Start or reset the software, and then add a
Particle Flow system.
2. Open Particle View.
3. In Particle View, go to Options menu > Track
UpdateandturnonUpdateProgress.
This lets you monitor calculation of the particle
system by highlighting actions in Particle View
as the system executes them.
4. In Particle View, Add a Keep Apart operator
(page 2–172) to Event 01.
Keep Apart is a fairly calculation-intensive
operator .
5. Go to frame 100 by clicking the right end of the
time slider track.
Thereisadelayasthesystemcalculatesall
particle motion between frames 0 and 100.
This is necessary because Par ticle Flow is a
history-dependentsystem.Atthesametime,
the actions in the system highlight briefly in
Particle View as they’re executed at e ach frame.
6. Go to frame 50 by clicking the center of the
time slider track.
There is a another delay as the system calculates
all par ticle mot ion b etween fr ames 0 and 50.
7. In Part icle View, drag a Cache operator from
the depot to Event 01. Insert it anywhere in
the event.
When you release the mouse button, there is
adelayastheCacheoperatorautomatically
caches particle motion from the start of the
animation to the cu rrent frame. Meanwhile,
each action highlights briefly at each frame.
8. Go to frame 20 or so.
The only operators that highlight are Cache
(very fast) and Display; there is no delay for
calculation. All fra mes between 0 and 50 have
been cached.
9. Go to frame 100.
The delay this time is a result of ca ching particle
motion for frames 50 to 100.
10. Jump to different frames, and drag the time
slider.
All particle motion is now cached, so no delays
occur. But if you change a setting’s value, the
Cache operator automatically recalculates and
storestheparticlemotion.
11. Go to f rame 100, and then, in Particle View,
click the Keep Apart operator and use the
keyboardtochangetheFalloffZonevalueto
8.0.
By default, the Cache operator automatically
updates the cache when you change any
parameters it stores. Thus, when you change
the Falloff Zone value at frame 100, it
recalculates and recaches the entire animation.
Next, you’ll briefly explore how manual caching
works.
12. Click the Cache operator and set Update to
Manually.
The Cache operator no longer updates the
stored data automatically when you change a
parameter.
13. Click the Keep Apart operator, change the
Falloff Zone value to 9.0, and then drag the
time slider.
There is no delay, because the animation is st i l l
playing back from the cached data. However,
thecacheddataisnowinvalid,becauseyou
changed a parameter in the particle system.