Adobe AFTER EFFECTS 5.5 Help Manual page 375

Adobe After Effects Help
Using Help | Contents
tones produced by the layer map. See "Using Min and Max options to adjust the output
range of a layer map (PB only)" on page 368.
The alpha channel in a layer map modifies the value before it's applied to the desti-
•
nation layer. Areas where the alpha channel is completely off (transparent areas of a
layer map) have no effect 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 options; see "Using Min
and Max options to adjust the output range of a layer map (PB only)" on page 368.
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 compo-
sition as the layer map. Otherwise, Particle Playground ignores any property settings.
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 interme-
diate shades, using just a few widely spaced shades such as 50% gray, black, and white.
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.
Creating an RGB layer map (PB 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
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.
Setting up a layer map in a composition (PB only)
Before you apply a layer map to a particle layer, the layer map and the particle layer must
be contained within the same composition, in a stacking order that will produce the
results you want.
To set up a layer map:
1 Add the layer map to the composition.
2 Do one of the following:
Using Help | Contents
| Index
| Index
Creating Particle Effects (PB only)
Back
Back
375
375