User Manual

Randomize and Random Seed
The Random Seed slider is used to seed all the variance and random number generators used
by the node when creating the particle system. Two pEmitter nodes with exactly the same
settings for all controls and the same random seed will generate exactly the same particle
system. Changing the random seed will cause variation between the nodes. Click the
Randomize button to automatically set a randomly chosen value for the Random Seed.
Number
This control is used to set the amount of new particles generated on each frame. A value of 1
would cause one new particle to be generated each frame. By frame 10, there would be a total
of 10 particles in existence (unless Particle Lifespan was set to fewer than 10 frames).
Animate this parameter to specify the number of particles generated in total. For example, if
only 25 particles in total are desired, animate the control to produce five particles on frame
0–4, then set a key on frame five to generate zero particles for the remainder of the project.
Number Variance
This modifies the amount of particles generated for each frame, as specified by the Number
control. For example, if Number is set to 10.0 and Number Variance is set to 2.0, the emitter will
produce anywhere from 9-11 particles per frame. If the value of Number Variance is more than
twice as large as the value of Number, it is possible that no particles will be generated for a
given frame.
Lifespan
This control determines how long a particle will exist before it disappears or ‘dies.’ The default
value of this control is 100 frames, although this can be set to any value. The timing of many
other particle controls is relative to the Lifespan of the particle. For example, the size of a
particle can be set to increase over the last 80% of its life, using the Size Over Life graph in the
Style tab of the pEmitter.
Lifespan Variance
Like Number Variance, the Lifespan Variance control allows the Lifespan of particles produced
to be modified. If Particle Lifespan was set to 100 frames and the Lifespan Variance to 20
frames, particles generated by the emitter would have a lifespan of 90–110 frames.
Color
This provides the ability to specify from where the color of each particle is derived. The default
setting is Use Style Color, which will provide the color from each particle according to the
settings in the Style tab of the pEmitter node.
The alternate setting is Use Color From Region, which overrides the color settings from the
Style tab and uses the color of the underlying bitmap region.
The Use Color From Region option only makes sense when the pEmitter region is set to use a
bitmap produced by another node in the composition. Particles generated in a region other
than a bitmap region will be rendered as white when the Use Color From Region option
is selected.
Position Variance
This control determines whether or not particles can be ‘born’ outside the boundaries of the
pEmitter region. By default, the value is set to zero, which will restrict the creation area for new
particles to the exact boundaries of the defined region. Increasing this control’s value above
0.0 will allow the particle to be born slightly outside the boundaries of that region. The higher
the value, the ‘softer’ the region’s edge will become.
Chapter – 103 Particle Nodes 2283