5

The Predictability of Particle Systems
When you create a particle system or modify a parameter of an existing particle system,
the path of each particle is immediately calculated and predetermined. Although the
number and motion of particles might seem random, they are completely predictable
based on that system’s parameters. Playing the same particle system twice with the
same parameters results in exactly the same particle motion. If you want to choose a
new predetermined set of random values, you can change the Random Seed setting
repeatedly until you obtain a result you like.
Using Multiple Cells in a Single Emitter
When you create a particle system from scratch, you don’t have to restrict yourself to
using just one cell. You can create a particle system that emits many kinds of overlapping
particles by placing multiple cells inside of a single emitter in the Layers list.
You can add as many cells as you want in a single emitter. Each cell has its own particle
cell parameters that govern how particles from that cell are created. When selected in
the Layers list, each cell displays its own Particle Cell Inspector. Particle systems with
multiple cells generate particles from each cell simultaneously, according to each cell’s
parameters.
For an example of using multiple cells in a single emitter, see Example 2: Creating Animated
Pixie Dust.
Additional cells can be created by selecting multiple layers when initially creating the
emitter, or by dragging additional source layers onto the emitter in the Layers list.
Note: When multiple sources are used to create a particle system, the resulting emitter
is positioned at the average of the sources’ positions.
Customizing a Particle System Emitter
When you create an emitter, the particle system starts working according to the default
parameters in its Emitter and Particle Cell Inspectors. You can use the Emitter HUD to
easily change the most important of these parameters to suit your needs.
To display the HUD for a particle emitter
µ
Select the emitter.
The HUD appears when you select the emitter. If the HUD does not appear, press F7.
Using the HUD to Create a Simple Smoke Effect
In this example, use the Emitter HUD to create a smoke effect. Use the emitter created
in Creating a Simple Custom Particle System.
677Chapter 14 Working with Particles