Creating An Rgb Layer Map For Particle Playground (Pro Only) - Adobe AFTER EFFECTS 7.0 Manual

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In Photoshop, an easy way to create a layer map is to create a layer with a black or white background, draw a
selection, and fill the selection with the opposite color. Blurring the entire layer softens the transition between
black and white values.
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You can set layer map values more precisely by painting shades of gray within a range from 0 (black) to 255 (white).
This is the tonal range of an 8-bit channel. To simplify painting or drawing, see if your image-editing program
provides or allows you to create a palette of 256 gray shades.
Note: While images created for use as displacement maps (in other effects or programs) often map tones to values on a
scale from –127 to +127, Particle Playground interprets tones of gray as values on a scale from 0.0 (black) to 1.0 (white).
If you're using images created as displacement maps, use the Min and Max controls to modify the range of tones produced
by the layer map. (See "Using Min and Max controls for Property Mappers (Pro only)" on page 511.)
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The alpha channel in a layer map modifies the value before it's applied to the destination layer. Areas where the
alpha channel is completely off (transparent areas of a layer map) don't affect on particle values. Areas where the
alpha channel has a partial value (semitransparent areas of a layer map) partially affect the particle value. For
example, if a layer-map pixel has a value of 10 and the layer-map alpha channel has a value of 127 (50%), the layer-
map pixel is affected by 50%, and its true value is 5. When you use the Persistent and Ephemeral Property
Mappers, the actual value applied to a particle is also affected by the range set for the Min and Max controls. (See
"Using Min and Max controls for Property Mappers (Pro only)" on page 511.)
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If you want to change any of the layer map's layer properties (Masks, Effects, or Transform), change them,
precompose the layer, and then use the resulting composition as the layer map. Otherwise, Particle Playground
ignores any property settings.
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The contrast between adjacent pixel values determines how smoothly the values change across the surface of the
layer map. To create smooth changes, paint using a soft or anti-aliased brush, or apply gradients. To create abrupt
changes, avoid intermediate shades, using just a few widely spaced shades such as 50% gray, black, and white.
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You can adjust overall edge contrast with blur or sharpen filters, if your painting or drawing program provides
them.
Note: If you want to edit individual pixels, open the layer map in the program you used to create it and make the change.
Before you apply a layer map to a particle layer, they must be in the same composition, in a stacking order that
produces the results you want. If you want particles to be visible in front of the layer map, make sure that the layer
with Particle Playground applied is in front of the layer map. If you don't want the layer map to be visible, hide it by
clicking the layer's eye icon

Creating an RGB layer map for Particle Playground (Pro only)

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 layer map 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 color layer.
When you apply an effect that can use each color channel as a separate layer map, you can still use a grayscale image;
the RGB channels will be identical.
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.
in the Timeline panel.
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