Instruction Manual

Chapter 14 Particles 545
Particle systems that use still images as their cell sources render in real time much faster than
systems that use video or animation clips. A still image is often all you need to create a compelling
particle system. Use the following guidelines when creating graphics for use as particles:
•
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-dened 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 predened alpha
channels. For more information on importing les with alpha channels, see About alpha
channels on page 172 .
Create animations to use as particle 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.
For example, if a clip is retimed in the Properties Inspector or with a Retiming behavior, the eect
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.
Use the following guidelines when creating animations for use as particles:
•
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.
•
Minimal compression: Ideally, QuickTime clips to be used as particles should be saved using
a high-quality codec, such as Animation, Uncompressed 8- and 10-bit 4:2:2, or ProRes 4444.
Other codecs can be used, but they might introduce unwanted artifacts depending on the
level of compression used.
There is an option to use random start frames, which causes the clips to play out of sync
relative to one another in the Canvas. There is also an option to play or not play the clip.
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