2009

Table Of Contents
For a particle object, you typically create two expressionsa creation expression
that initializes an attribute value in the first frame, and a runtime expression
that controls the attribute value in subsequent frames. (Creation and runtime
expressions exist only for particle objects, not for other types of objects.)
This lesson described how to color stationary particles as a simple way to
describe creation and runtime expressions. However, its more typical to use
particle expressions to:
Create sophisticated particle motion and life span; for example, the
movement and fading of exploding fireworks.
Create complex colors for emitted particles, for example, rocket exhaust
flames.
Create complex colors and movement of particles following collision with
geometry, for example, sparks resulting from fired bullets.
Creating such effects requires experience and experimentation. Expression
writing can be as complex as computer programming. A detailed
understanding of expression execution and syntax is essential. You also
need to become familiar with the built-in mathematical functions such as
the sphrand function introduced in this lesson.
For further information and related techniques, refer to the Maya Help.
590 | Chapter 12 Expressions