Apple Motion 3 - Manual (Page 733)

Chapter 8 Working with Particles 733
Note: Whatever is selected in the Show Particles As pop-up menu appears in your final
render.
Random Seed: Although particle systems seem random, they’re actually deterministic.
This means that the random variation in each particle system is created based on the
number shown here. Unless this seed number is changed, a particle system with the
same parameter settings always plays back with the same motion. If you don’t like the
current random motion or distribution of the particle system, you can change the seed
number by typing a new number or clicking Generate. This changes the random
calculations performed for that system for all randomness parameters.
For more information about the random nature of particle systems, see “ The
Predictability of Particle Systems ” on page 695.
Particle Source: In particle systems with more than one cell, a parameter representing
each cell appears at the bottom of the Emitter tab. Each cell parameter has a checkbox
you can use to enable or disable that cell, a name field, and an image well for that
object.
Additional Cell Parameters for QuickTime Movies
If you create a particle system using a QuickTime movie as a cell, additional parameters
appear. These five parameters are:
Play Frames: This checkbox controls playback. If it’s turned on, it loops the playback of
the animation or movie clip used to generate each particle. If it’s turned off, particles
are generated using the still frame specified by either the Random Start Frame
parameter or the Source Start Frame parameter.
Random Start Frame: This checkbox introduces variation into animated particles
generated from QuickTime objects. If it’s turned on, each newly generated particle
begins at a different frame of the animation. Stills are chosen randomly if Play Frames is
turned off.
Source Start Frame: Chooses the frame to begin animation, if Play Frames is turned on,
or the still frame to display if Play Frames is turned off. This parameter only appears if
Random Start Frame is turned off.
Hold Frames: The number of times each frame of the source movie is repeated during
playback. The larger the Hold Frames value, the slower your playback.
Hold Frames Randomness: Varies the number of frames to “hold.” See the Hold Frames
parameter description.