Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 500

AFTER EFFECTS CS3 494
User Guide
When you use another layer as a source for particles, Particle Playground ignores any changes you made to that layer
within that composition, such as changing the Position values. Instead it uses the layer in its original state. To keep
changes for a layer when you use it as a particle source, precompose the layer.
Particle content and particle generators
Particle Playground can generate three kinds of particles: dots, a layer, or text characters. You can specify only one
kind of particle per particle generator.
Create particles by using the Cannon, the Grid, the Layer Exploder, and the Particle Exploder. The Grid creates
particles in an organized grid format with straight rows and columns. The exploders create particles randomly, like
firecracker sparks.
The particle generators set the attributes of particles at the moment they are created. After that, particle behavior is
influenced by the Gravity, Repel, Wall, Exploder, and Property Mapper controls. For example, if you want particles
to stick to grid intersections, you might use the Static Friction option in the Persistent Property Mapper to hold
particles in place. Otherwise, as soon as particles are created, they begin moving away from their original grid
positions.
Cannon controls
The Cannon is on by default; to use a different method to create particles, first turn the Cannon off by setting
Particles Per Second to zero. The Cannon creates particles in a continuous stream.
Specifies the (x,y) coordinates from which particles are created.
Position
Sets the size of the Cannon's barrel radius. Negative values create a circular barrel, and positive values
Barrel Radius
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.
Specifies how often particles are created. A value of 0 creates no particles. A high value
Particles Per Second
increases the density of the particle stream. If you don't want the Cannon to fire continuously, set keyframes for this
control so that the value is 0 at the times when you don't want to create any particles.
Sets the angle at which particles are fired.
Direction
Specifies how much each particle's direction deviates randomly from the cannon
Direction Random Spread
direction. For example, specifying a 10-degree spread sprays particles in random directions within +/–5˚ 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˚.
Specifies the initial speed of particles in pixels per second as they emanate from the Cannon.
Velocity
Specifies the amount of random velocity of particles. A higher value results in more
Velocity Random Spread
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.
Sets the color of dots or text characters. This control has no effect if you use a layer as the particle source.
Color
Sets the radius of dots, in pixels, or the size of text characters in points. This control has no effect if
Particle Radius
you use a layer as the particle source.
Grid controls
The Grid creates a continuous plane of particles from a set of grid intersections. The movement of Grid particles is
completely determined by the Gravity, Repel, Wall, and Property Mapper settings. By default, the Force control of
Gravity is on, so Grid particles fall toward the bottom of the frame.