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120 Chapter 11: Space Warps and Particle Systems
the total number of particles, separately for
viewport display and rendering.
Tip: Tospeedupanimationplaybackwhenyou’re
not adjusting parameters, use the Cache operator
(see the following item).
Is there a way to pre-ca l culate portions of
a particle simulation, as in "bak ing" the
animation?
Ye s . P a r t i c l e F l o w ’ s Cache operator (page 2–197)
lets you store all or part of a particle animation
in memory, and then play back the animation
from memor y rather than having to recalculate
particle motion. This makes it much faster to jump
between different parts of the animation. You can
even save the cached animation to disk as part of
the scene file.
What else can I do to optimize performance?
Particle Flow can place heavy processing and
resource demands on your computer . For optimal
performance, the most important thing you can
do is to use the fastest available CPU. Also, when
using particle systems with many particles, install
as much memory as possible i n your computer,
especially if you’re using caching.
Other ways to improve performance include
reducing the percentage of viewport particles with
the Quantity Multiplier setting, and temporarily
disabling flows and actions that you’ re not
currently working with. When m aking parameter
changes, return to the first frame and play forward,
or set Particle View > Options menu > Update
Type to “Forward”. That way, if you change
a setting, the particle system is not forced to
recalculate its state from the very beginning. The
change will affect only animation f rom the current
frame forward. On the other hand, the result could
be misleading, because you won’t be able to see
thedifferencerightaway.
Also, be cautious when using spawning; it can
quickly cr eate very large numbers of particles,
especially when you use the By Travel Distance
option in the Spawn test (page 2–230).
How do I use Particle Flow to make an object
explode?
Particle Flow doesn’t have a fragmentation
operator, but by utilizing PArray in a Birth Script
operator, you can implement fragmentation
in Particle Flow. You can find an example
scene, with a commented script operator, in
the file s criptfragmentationwithcache.max,
on the install disc in the direc tor y
Samples\Scenes\Version6Features\Scenes\Particle
Flow\Fragments.
How can I control the accuracy of the Particle
Flow simulation?
On the command panel > System Management
rollout (page 2–139) of the PF Source icon, you
can adjust the integration step independently for
viewport playback and rendering. The smal ler
the integration step, the more times Particle Flow
calculates particle motion per frame, resulting in
greater accuracy at the cost of calculation time.
Can I use M AXScript to affect par ticles?
Yes. Par ticle Flow includes a Script operator (page
2–208) and test (page 2–229),aswellasaBirth
Script operator (page 2–145),thatletyoufully
customize the particle system. Each scriptable
action includes a sample script, which also lists all
relevant scriptable functions. You can also control
parameters of the Force operator (page 2–204)
and Keep Apart operator (page 2–172) with script
wiring, described in the respective topics.
In addition, you can execute a scr ipt at each
integration step, and another just before each
frame is v iewed or rendered; see Script rollout
(page 2–139).