Adobe AFTER EFFECTS 5.5 Help Manual page 355

Adobe After Effects Help
Using Help | Contents
When creating particles using the Cannon, you can adjust the following options:
Position Determines the X, Y coordinates from which particles are created.
Barrel Radius Sets the size of the Cannon's barrel radius. Negative values create a circular
barrel, and positive values create a square barrel. For a narrow source such as a ray gun,
specify a low value. For a wide source such as a school of fish, specify a high value.
Particles Per Second Determines how often particles are created. A value of 0 (zero)
creates no particles. A high value increases the density of the particle stream. If you don't
want the Cannon to fire continuously during the composition, set keyframes for this
property so that the value is 0 at the times when you don't want to create any particles.
Direction Sets the angle at which particles are fired.
Direction Random Spread Determines how much each particle's direction deviates
randomly from the Cannon Direction. For example, specifying a 10-degree spread sprays
particles in random directions within +/–5 degrees of the Cannon Direction. For a highly
focused stream such as a ray gun, specify a low value. For a stream that widens quickly,
specify a high value. You can specify up to 360 degrees.
Velocity Determines the initial speed of particles in pixels per second as they emanate
from the Cannon.
Velocity Random Spread Determines the amount of random velocity of particles. A
higher value results in more variation in the velocity of particles. For example, if you set
Velocity to 20 and Velocity Random Spread to 10, particles leave the Cannon at velocities
ranging from 15 to 25 pixels per second.
Color Sets the color of dots or text characters. This setting has no effect if you use a layer
as the particle source.
Particle Radius/Font Size Sets the radius of dots, in pixels or the size of text characters in
points. This setting has no effect if you use a layer as the particle source.
To turn off the particle stream:
1 In the Effect Controls window, click the right-facing triangle next to Cannon so that it
points downward.
2 Click Particles Per Second, type 0 (zero), and click OK.
Particle Playground Grid (PB only)
The Grid creates a continuous plane of particles from a set of grid intersections. Grid
particles are created without any velocity, so the movement of Grid particles is completely
determined by the Gravity, Repel, Wall, and Property Mapper settings. By default, Grid
particles fall toward the bottom of the frame because by default the Force property of
Gravity is on.
With the Grid, a new particle appears on every frame at each grid intersection. You can't
adjust this frequency, but if you want the grid to stop generating particles at specific
times, set the Particle Radius/Font Size option to 0, or use keyframes to animate the value
of the Particles Across and Particles Down properties. To make more particles appear each
frame, increase the values for Particles Across and Particles Down.
Note: By default, the Cannon is on and the Grid is off. If you are using the Grid and want to
stop the Cannon from generating particles, turn off the Cannon by setting its Particles Per
Second to 0 (zero).
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