Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 505

Gravity controls
Use Gravity controls to pull existing particles in a direction you specify. Particles accelerate in the direction of gravity.
Apply in a vertical direction to create falling particles, such as rain or snow, or rising particles, such as champagne
bubbles. Apply in a horizontal direction to simulate wind.
Specifies the force of gravity. Positive values increase the force, pulling particles more strongly. Negative values
Force
reduce the force.
Specifies a range of randomness for the Force. At zero, all particles fall at the same rate. At a
Force Random Spread
higher value, particles fall at slightly different rates. Although pure gravity accelerates all objects equally, increasing
the Force Random Spread value can produce more realistic results with subjects such as leaves falling through air,
where there is enough air resistance to vary the leaves' rates of descent.
Specifies the angle along which gravity pulls. The default is 180˚, which simulates the real world by pulling
Direction
particles toward the bottom of the frame.
Specifies a subset of the layer's particles to which Gravity applies.
Affects
Repel controls
Repel controls specify how nearby particles repel or attract each other. This feature simulates adding a positive or
negative magnetic charge to each particle. You can specify which particles, layers, or characters are the repelling force
and which are repelled.
Note: If you want to repel an entire layer of particles away from a specific area, use the Property Mapper controls, Wall
or Gradient Force.
Specifies the repel force. Greater values repel particles with more force. Negative values result in particle
Force
attraction.
Specifies the radius (measured in pixels) within which particles are repelled. Another particle must be
Force Radius
within this radius to be repelled.
Specifies which particles act as the repellers or attractors to another subset you specify by using the Affects
Repeller
control.
Specifies a subset of the layer's particles to which repulsion or attraction applies.
Affects
Wall controls
Wall controls contain particles, limiting the area within which particles can move. A wall is a closed mask that you
create by using a mask tool, such as the Pen tool. When a particle hits the wall, it bounces off at a velocity based on
the force with which it hit.
Specifies the mask to use as the wall. You can create a new mask by drawing one on the effect layer.
Boundary
Affects controls
Many Particle Playground controls include Affects controls. Affects controls specify which particles are affected by
the encompassing control. For example, the Affects controls within the Particle Exploder controls specify which
particles the Particle Exploder affects.
Specifies the particle generator or combination of particle generators whose particles you want to
Particles From
affect.
Specifies the layer map that influences which particles are affected.
Selection Map
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