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248 Chapter 11: Space Warps and Particle Systems
Works in combination with the particle system’s
timing parameters.
• When the number of particles reaches the
Render Count value, particle creation is
suspended until some particles die.
• When enough particles die, particle creation
resumes until Render Count is reached again.
Fla ke S i ze—Size of a particle in the active units.
Speed—Initial velocity of each particle as it lea ves
the emitter. Particles travel at this speed unless
they are affected by a par ticle system space warp.
Variation—Varies the initial speed and direction of
particles.ThegreatertheVariation,thebroader
the area of snowfall.
Tu mble —Amount of random rotation for
snowflake particles. This parameter can range
from0to1.At0,flakesdonotrotate;at1,they
rotate the most. The axis of rotation is generated
randomly for each particle.
Tu mble Rate—Speed at w hich snowflakes rotate.
ThegreatertheTumbleRate,thefasterthe
rotation.
Flakes, Dots, or T i ck s—Select how particles are
displayed in viewports. The display setting does
not affect how particles are rendered. Flakes are
star-shaped snow flakes, dots are p oints, ticks are
small plus signs.
Render group
Six Point—Each particle is rendered as a
six-pointed star. E ach side of the star is a face to
which you can assign a material. This is the default
setting for rendering.
Triangle—Each particle is rendered as a triangle.
Onlyonesideofthetriangleisafacetowhichyou
can assign a material.
Facing—Particles are rendered as square faces
whose width and height equals the Drop Size.
Facing particles always face the camera (or
the user’s perspective). They are provided
especially for use with material maps. Use
with an appropriate opacity map for bubbles or
snowflakes.
Note: Facing works correctly only in a perspective
or camera view.
Timing group
Timing parameters control the "birth and de ath"
rates of emitted particles.
At the bottom of the Timing group is a line that
displays the maximum sustainable r ate. This value
is based on the Render Count and the lifetime of
each particle. To be precise:
maximum sustainable rate=Render Count/Life
Becausethenumberofparticlesinaframenever
exceeds Render C ount, if the Bir th Rate exceeds
the maximum rate, the system will run out of
part icles, pause until some die off, and then start
again, generating bursts or spurts of particles.
Start—Numberofthefirstframewhereparticles
appear.
Life—The lifetime of a particle, in number of
frames.
Birth Rate—The number of new particles born per
frame.
If this is less than or equal to the maximum
sustainablerate,theparticlesystemgenerates
an even flow of particles. If it is greater than the
maximum r ate, the particle system generates
particles in bursts.
You can animate the Birth Rate parameter.
Co nstant—When on, Birth Rate is unavailable
andthebirthrateusedequalsthemaximum
sustainable rate. When off, Birth Rate is available.
Default=on.