Adobe After Effects CS4 - Manual (Page 568)

562 USING AFTER EFFECTS CS4
Effects and animation presets
Last updated 12/21/2009
Bubble Velocity faces the bubble in the direction of its motion. This setting is the most useful for flocking-style
animations.
Environment Map Specifies the layer that is reflected in the bubbles. If you want to use this layer only for the reflection,
turn off the video switch for a layer.
Reflection Strength Controls how much of the selected Environment Map is reflected in the bubbles. The higher the
value, the more the reflection obscures the original bubble texture. Reflections appear only on opaque pixels, so
bubbles with high amounts of transparency, such as the Spit preset, don’t reflect much.
Reflection Convergence Controls how much your Environment Map is distorted as it is mapped onto the bubbles. A
value of 0 projects the map flat on top of all of the bubbles in the scene. As the value increases, the reflection distorts
to account for the spherical shape of each bubble.
Flow Map controls
The Flow Map controls specify the map that the flow of the foam follows:
Flow Map Specifies the layer used to control the direction and speed of the bubbles. Use a still image layer; if you select
a movie as the flow map layer, only the first frame is used. A flow map is a height map based on luminance: White is
high, and black is low. White is not infinitely high; if a bubble travels fast enough, it can travel past a white obstacle.
Make sure that the map is a little blurry; sharp edges can create unpredictable results. For example, to make bubbles
flow through a canyon, create a flow map with a white canyon rim, a black canyon, and blurry gray walls. Use wind to
blow the bubbles in the direction you want them to flow, and the walls of the canyon contain them. You can also use
a gentle gradient on the floor of the canyon to control the flow direction.
Note: If the bubbles don’t follow the map, use the Simulation Quality control. Also, try blurring the flow map a little to
make sure that it does not have excessively abrupt edges.
Flow Map Steepness Controls the difference between white and black as they are used to determine steepness. If the
bubbles are ricocheting randomly off the flow map, decrease this value.
Flow Map Fits Specifies whether the flow map is relative to the layer or to the universe. The flow map resizes itself to
fit whichever you specify. This control is useful when you want to enlarge the universe but the flow map is designed
for a particular layer, or when you want the bubbles to start outside the frame and be affected by the flow map as they
arrive in the frame.
Simulation Quality Increases the precision, and therefore the realism, of the simulation. However, the higher the value,
the longer the composition takes to render. Normal generally produces good results and takes the least amount of time
to render. High returns better results but takes longer to render. Intense increases the rendering time but produces
more predictable bubble behavior. Use this option if the bubbles aren’t following the flow map. It often solves problems
of erratic behavior that can occur with small bubbles, high bubble speeds, and steep slopes.
Particle Playground effect
The Particle Playground effect lets you animate a large number of similar objects independently, such as a swarm of
bees or a snow storm. Use the Cannon to create a stream of particles from a specific point on the layer, or use the Grid
to generate a plane of particles. The Layer Exploder and Particle Exploder can create new particles from existing layers
or particles. You can use any combination of particle generators on the same layer.
David Van Brink provides a video walkthrough and downloadable example project on the omino website that show
several things that you can do with the Particle Playground effect, including how to use the Kinetic Friction ephemeral
property mapper.
Brian Peterson provides a tutorial on the Videomaker website that shows how to use the Particle Playground effect to
create a flock of birds.