Adobe After Effects CS4 - Manual (Page 566)

560 USING AFTER EFFECTS CS4
Effects and animation presets
Last updated 12/21/2009
upper-left corner of the screen if you don’t select Zoom Producer Point. If you select Zoom Producer Point, the point
moves with the universe as it is zoomed out, and the point ends up closer to the center of the screen.
Production Rate Determines the rate at which bubbles are generated. This control does not affect the number of
bubbles per frame. Rather, the rate is the average number of bubbles generated every 30th of a second. Higher numbers
yield more bubbles.
If a large number of bubbles appear in the same point at the same time, some may pop. If you want a lot of foam,
increase the values for Producer X Size and Producer Y Size so that the bubbles don’t immediately pop each other.
Bubbles controls
Size Specifies the average size for adult bubbles. Size Variance, Bubble Growth Speed, and Random Seed also affect
the size of a bubble in any particular frame.
Size Variance Specifies the range of possible bubble sizes. This control uses the Size value as the average and creates
smaller-than-average and larger-than average bubbles by using the range you specify here. For example, a default
bubble Size of 0.5 and default Size Variance of 0.5 generate bubble sizes ranging from 0 to 1 (0.5 –.5 = 0 and 0.5 + 0.5 = 1).
Lifespan Specifies the maximum life of a bubble. This value is not absolute; if it were, the bubbles would all pop after
the same lifespan, as if they were hitting a wall. Rather, this value is a target lifespan; some bubbles pop early, and others
may last until the end.
Bubble Growth Speed Specifies how fast a bubble reaches full size. When a bubble is released from the producer point,
it generally starts out rather small. If you set this value too high and you specify a small producer area, the bubbles pop
each other, and the effect generates fewer bubbles than expected.
Strength Influences how likely a bubble is to pop before it reaches its Lifespan limit. Lowering the Strength for a
bubble makes it more likely to pop early in its life, when forces like wind and flow maps act upon it. Lower values are
good for soap bubbles. The highest value is recommended for flocking animations.
Set this value low, and set Pop Velocity high to create chain reactions of popping bubbles.
Physics controls
The Physics controls specify the motion and behavior of the bubbles:
Initial Speed Sets the speed of the bubble as it is emitted by the producer point. The other Physics parameters affect
this speed.
Low Initial Speed values in conjunction with the default producer size don’t affect the results much because the
bubbles bounce off each other. For more control over initial speed, increase the values for Producer X Size and
Producer Y Size.
Initial Direction Sets the initial direction in which the bubble moves as it emerges from the producer point. Other
bubbles and other Physics controls also affect the direction.
Wind Speed Sets the speed of the wind that pushes the bubbles in the direction specified by Wind Direction.
Wind Direction Sets the direction in which the bubbles blow. Animate this control to create turbulent wind effects.
Wind affects bubbles if Wind Speed is greater than 0.
Turbulence Applies small random forces to the bubbles, making them behave chaotically.
Wobble Amount Randomly changes the shape of bubbles from perfectly round to a more natural elliptical shape.
Repulsion Controls whether bubbles bounce off each other, stick to each other, or pass through each other. At a value
of 0, bubbles don’t collide; they pass through each other. The higher the Repulsion value, the more likely bubbles are
to interact with each other when they collide.