Apple Motion 4 - Manual (Page 646)

Note: When you use an image as a particle cell source and set a low Scale value, it is
recommended that you set the render quality in the Render pop-up menu (in the Status
Bar) or the View menu to Best (choose View > Quality > Best).
Scale Randomness: A slider that defines an amount of variance in the scale of generated
particles. A value of 0 results in no variance—all particles from the selected cell emerge
with the same size. A value greater than 0 introduces a variance defined by the Scale
parameter, plus or minus a random value falling within the Scale Range. The disclosure
triangle of the Scale parameter reveals separate X and Y subparameters, which can be
used to set the width and height of the Scale Range separately.
Attach To Emitter: A slider that determines how closely particles follow the position of
a moving emitter. If set to zero, particles follow their own path after being emitted,
resulting in particles that trail along the motion path the emitter is following. If this
parameter is set to 100, in the absence of other behaviors, all generated particles follow
along with the emitter, surrounding it in a moving cloud of particles.
Attach to Emitter set to 0 (zero) Attach to Emitter set to 100
Play Frames: This parameter appears if the particle system was created from a QuickTime
movie. This checkbox controls playback. If selected, playback of the animation or movie
clip used to generate each particle loops. If deselected, 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 appears if the particle system was created from a
QuickTime movie. Introduces variation into animated particles generated from QuickTime
objects. If selected, each newly generated particle begins at a different frame of the
animation. Stills are chosen randomly if Play Frames is deselected.
Source Start Frame: This parameter appears if the particle system was created from a
QuickTime movie. Chooses the frame to begin animation, if the Play Frames checkbox is
selected, or the still frame to display if Play Frames is deselected. This parameter only
appears if Random Start Frame is deselected.
646 Chapter 11 Working with Particles