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242 Chapter 11: Space Warps and Particle Systems
is based on the Render Count and the lifetime of
each p art icle. To be precise:
maximum sustainable rate=Render C ount/Life
Becausethenumberofparticlesinaframenever
exceeds Render Count, if the Birth Rate exceeds
the maximum rate, the system will run out of
part icles, pause until some die off, and then start
again, generating particles in bursts or spurts.
Start—Numberofthefirstframewhereparticles
appear.
Life—The lifetime of each particle, in number of
frames.
Birth Rate—The number of new par t icles born per
frame.
If this is less than or equal to the maximum
sustainable rate, the par ticle system generates
an even flow of part icles. If it is greater than the
maximum rate, the particle system generates
particles in bursts.
You c an animate the Birth Rate par ameter.
Co nstant—When on, Birth Rate is unavailable
andthebirthrateusedequalsthemaximum
sustainable rate. When off, Birth Rate is available.
Default=on.
TurningConstantoffdoesnotmeanthatthe
birth rate varies automatically; the birth rate
remainsconstantunlessyouanimatetheBirth
Rate parameter.
Emitter group
The emitter specifies the area w here particles
appear in the scene. I t has a geometry you can
display in viewports, but it isn’t renderable.
The emitter is displayed as a rectangle with a
vector pointing out of one side. The vector shows
the direction in which the system emits particles.
Width and Length—You i mplicitly set the initial
value of these parameters when you dr ag in a
viewport to create the emitter. You can adjust the
values in t he rollout.
The space occupied by the particle system at any
given time is the result of a combination of its
initial parameters (such as size of the emitter, and
speed and variation of emission) and any space
warps that have been applied.
Hide—Turn on to hide t he emitter in viewports.
When Hide is off, the emitter is displayed in
viewports. The emitter is never rendered.
Default=off.
Snow Particle System
Create pa nel > Geometry button > Choose Particle
Systems from the drop-down list. > Object Type rollout >
Snow
Create menu > Particles > Snow
Snow simulates fal ling snow or confetti. The snow
system is similar to Spray, but it has additional
parameters to generate tumbling snowflakes, and
itsrenderingoptionsaredifferent.