Adobe After Effects - Manual (Page 578)

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Note:
Note:
The alpha channel in a control layer modifies the color values in the control layer before Particle Playground uses the control layer’s pixel values.
Areas where the alpha channel value is 0 (transparent areas of a control layer) don’t affect particle values. Areas where the alpha channel has a
value greater than 0 (semitransparent and opaque areas of a control layer) affect the particle value to a degree proportional to the value of the
alpha channel. When you use the Persistent and Ephemeral Property Mapper property groups, the range set for the Min and Max controls also
affects the value applied to a particle.
Particle Playground can extract brightness values separately from the red, green, and blue channels in an image. If you want to create different
layer maps for each channel, use a program that can edit individual color channels, such as Adobe Photoshop, and then paint or paste each layer
map into its own channel. Save the control layer as an RGB image in a format After Effects can import. The image may look unusual when viewed
in RGB mode, because it’s intended to be used as a single hidden layer containing three different layer maps, not as a visible image layer.
If you already have three separate images, you can combine them into a single RGB file by using the Set Channels effect. Set Channels can
load each image into its own channel in a combined file, making it suitable for use as an RGB layer map.
Improving performance with Particle Playground
Keep in mind the following when working with the Particle Playground effect:
When you’re generating a Particle Playground effect, keep an eye on the Info panel to see how many particles are being produced. If an
effect contains more than 10,000 particles, it can greatly slow rendering. If you notice performance problems, set Particles Per Second and/or
Particles Down to relatively low values (in the range 1–100).
The Grid and Layer Exploder generate particles on every frame, which may generate too many particles for the effect you’re creating and
slow down rendering. To avoid continuous particle generation, animate these controls to decline to zero over time: Layer Exploder, Radius of
New Particles, Grid Width and Height, Particle Radius, and Font Size. Then Particle Playground generates new particles only at the start of a
sequence.
When you apply a Particle Playground effect to a layer, the particle positions aren’t limited to the bounds of that layer. To control particles
that you can’t see or that appear near the edge of the image, use a Selection or Property Map that’s larger than the area of the Particle
Playground layer. Also, note that After Effects takes the alpha channel of an image map into account. If you want transparent areas of your
map to affect the particles, precompose the map layer with a black solid behind it.
To specify field rendering with a Particle Playground effect, select Enable Field Rendering in the Particle Playground options dialog box. Then
Particle Playground calculates the simulation at double the frame rate of the current composition, which is what field rendering requires.
Shatter effect
For information on properties shared by several of the Simulation effects, see Common Lighting controls and Material controls .
The Shatter effect explodes images. Use the controls for the effect to set explosion points and adjust the strength and radius. Anything outside the
radius doesn’t explode, leaving portions of the layer unaltered. You can choose from a variety of shapes for the shattered pieces (or create custom
shapes) and extrude the pieces to give them bulk and depth. You can even use a gradient layer to precisely control the timing and order of an
explosion. For example, you can import a logo and use Shatter to blow a logo-shaped hole in a layer.
Brian Maffitt provides more than two hours of video explanation and tutorials for the Shatter effect in a series of videos from Total Training . The
interface has changed since these videos were created, but the information is still valuable.
To reverse the temporal direction of the Shatter effect (that is, have the pieces come together instead of fly apart), apply the effect,
precompose the layer, and then time-reverse the precomposition layer.
This effect works with 8-bpc color.
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