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Graphics Size
If you are unsure what size you want your particles to be, it’s a good idea to make your
graphics larger rather than smaller. Increasing the size of particles beyond the size of the
original graphic can introduce unwanted artifacts. One caveat, however, is that the larger
the cell source size, the slower your playback performance.
Particle Edges
The quality of the edges of your graphics can be extremely important for creating
convincing particles. Soft, translucent edges might look better than hard, over-defined
ones.
Object Color
By default, particles are created using the original colors of the image used as the cell. If
necessary, you can tint the emitted particles using the Color Mode parameters in the
Emitter and Particle Cell Inspectors. Choose between tinting all particles with a single
color or creating a gradient tint that changes color over time. You can also choose to
apply a Library gradient to the particles. Tinting particles applies the tint color uniformly
over the entire particle system.
Alpha Channels
Always create graphics that you want to use as cells with predefined alpha channels. For
more information on importing files with alpha channels, see More About Alpha Channels.
Creating Animations to Use as Cells
You can also use QuickTime movies as cells. For example, you can create an animation
in Motion, render it as a QuickTime movie, and import it into another Motion project to
use as a cell. In general, the same recommendations for creating still graphics apply to
the creation of animation or video clips you intend to use as cells, but there are additional
considerations.
If a clip is retimed in the Properties Inspector or with a Retiming behavior, the effect of
the retiming is carried through to the particle system.
Note: Using a movie as the source cell for an emitter can impact your project’s playback
performance.
Looping Clips
Particles created from QuickTime clips loop over and over for the duration of each particle’s
life. If the clip you use doesn’t loop well, there will be a jump cut at every loop point.
Another option is to use very short movies to introduce randomness into the appearance
of the particle system.
689Chapter 14 Working with Particles