Apple Motion 4 - Manual (Page 624)

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 may introduce unwanted artifacts. One caveat, however, is that the larger
the cell source size, the slower your interactivity.
Particle Edges
Keep in mind that 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 being used as the
cell. If necessary, you can tint the emitted particles using the Color Mode parameters in
the Emitter and Particle Cell tabs. Choose between tinting all particles by 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.
Create Graphics with an Alpha Channel
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 has been retimed, in the Properties tab or with a Retiming behavior, the effect of
the retiming is carried through to the particles system.
Note: Keep in mind that using a movie as the source cell for an emitter may impact your
project’s interactivity.
Create Clips That Loop
Particles created from QuickTime clips loop over and over for the duration of each
individual 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.
624 Chapter 11 Working with Particles