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Play Frames: This checkbox, which appears if the particle system was created from a
QuickTime movie, 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 the Random Start Frame parameter or the Source Start Frame
parameter.
Random Start Frame: This checkbox, which 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 slider is available if the particle system was created from a
QuickTime movie, and Random Start Frame is deselected. Use it to set the start frame of
the animation (if the Play Frames checkbox is selected) or the still frame to display (if the
Play Frames checkbox is deselected).
Hold Frames: This slider, available if the particle system was created from a QuickTime
movie, sets 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: This slider, available if the particle system was created from
a QuickTime movie, varies the number of frames to “hold.”
Show Particles As: Use this pop-up menu to view particles in different preview modes,
or as they actually appear. These nonimage modes play more efficiently when viewing
a complex particle system and also provide other ways of analyzing particle motion. By
default, this parameter is set to Image, which displays each particle as it is supposed to
appear. There are four menu items:
• Points: Each particle is represented by a single point. This is the fastest preview mode
and is useful for displaying the type and speed of particle motion in a system. When
selected, the Point Size parameter is revealed.
714 Chapter 14 Working with Particles