Apple Motion 2 - Manual (Page 584)

584 Chapter 8 Working With Particles
The duration of the cell actually controls the duration over which new particles are
generated. You can change a cell’s duration by dragging either its position or its In and
Out points in the Timeline. In this way, you can adjust the timing that defines when
each cell’s particles emerge.
For example, you can create a particle system that simulates an explosion by offsetting
the appearance of three different types of particles. First, dense white particles emerge
from the center. Half a second later, more diffuse orange particles appear around a
larger area. One second after that, small sparks emerge from underneath both of these
layers as they fade away.
You can offset a cell in the Timeline or mini-Timeline to start before the emitter. This
creates a “preroll” in which the particle simulation starts before the particles are drawn.
01112.book Page 584 Sunday, March 13, 2005 10:36 PM