2009

during the event. As the event transpires, Particle Flow continually evaluates
each operator in the list and updates the particle system accordingly.
To achieve more substantial changes in particle properties and behavior, you
can create a
flow on page 7983. The flow sends particles from event to event
using
tests on page 8147, which let you wire on page 8170 events together in series.
A test can check, for example, whether a particle has passed a certain age, how
fast it's moving, or whether it has collided with a deflector. Particles that pass
the test move on to the next event, while those that don't meet the test criteria
remain in the current event, possibly to undergo other tests.
NOTE Operators and tests are known collectively as actions on page 7897.
Following are the principal sections in the Particle Flow documentation:
Using Particle Flow on page 2796
Particle Flow User Interface on page 2811
Actions on page 2838
See also:
■
Non-Event-Driven Particle Systems on page 3002
How Particle Flow Works
Particle View on page 2811 is the primary interface for building and modifying
Particle Flow systems. The first event in the system is always a global event,
whose contents affect all particles in the system. It has the same name as the
Particle Flow source icon. By default, the global event contains a single Render
operator that specifies rendering properties for all particles in the system. You
can add other operators here to have them act globally, such as Material,
Display, and Speed. When you use an operator globally, be sure not to use
the same operator locally (that is, in any other events in the system) to avoid
potential conflicts.
The global event also serves as the Particle View representation of the particle
system. You can create a new system by duplicating this event, or by adding
an Empty Flow or Standard Flow. Conversely, if you clone the Particle Flow
icon in a viewport, or add a new PF Source, the new system appears in Particle
View as well.
The second event is called the birth event, because it must contain a Birth
operator. The Birth operator should exist at the top of the birth event, and in
2796 | Chapter 14 Space Warps and Particle Systems