2009

Actions can also apply forces to particles (1), specify collision effects (2), and alter
surface properties (3).
In this way, the particle continues to travel through the system. Due to the
flexible nature of schematic construction in Particle Flow, a particle may be
redirected to the same event several times. But at some point, you might want
the particle's life to end. For this purpose, you'd use the
Delete operator on
page 2848 or the
Collision Spawn test on page 2964 or Spawn test on page 2991.
Otherwise, the particle lives throughout the entire animation.
Particle age can be used to kill a particle.
As a particle moves through the system, it's accompanied by a number of
channels. For example, each particle has a speed channel that defines how
fast it moves, and a material ID channel that lets Particle Flow know which
sub-material to apply to it. However, the material itself is not defined by a
channel, but by a Material operator that acts locally or globally. Properties
that are defined by channels persist, unless altered by an action. For example,
the
Material Dynamic operator on page 2925 can change a particle's material
ID. In effect, by setting up a particle diagram and modifying how particles
look and act during the animation, youre deciding how channel values change
based on events and animation keyframes.
2800 | Chapter 14 Space Warps and Particle Systems