Adobe After Effects CS4 - Manual (Page 183)

177 USING AFTER EFFECTS CS4
Layers and properties
Last updated 12/21/2009
Note: Sometimes, when layers are aligned edge-to-edge, seams can appear between the layers. This is especially an issue
with 3D layers that are joined to one another at the edges to build a 3D object. When the edges of a layer are anti-aliased,
there's some partial transparency at the edges. When two areas of 50% transparency overlap, the result is not 100%
opacity but 75% opacity, because the default operation is multiplication. (50% of the light gets through one layer, and
then 50% of the remainder gets through the next layer, so 25% gets through the system.) This is like partial transparency
in the real world. But, in some cases, you don't want this default blending. You want the two 50% opacity areas to combine
to make a seamless, opaque join. You want the alpha values to be added. In these cases, use the Alpha Add blending mode.
Luminescent Premul Prevents clipping of color values that exceed the alpha channel value after compositing by adding
them to the composition. Useful for compositing rendered lens or light effects (such as lens flare) from footage with
premultiplied alpha channels. May also improve results when compositing footage from matting software from other
manufacturers. When applying this mode, you may get the best results by changing interpretation of the
premultiplied-alpha source footage to straight alpha.
Layer styles
Photoshop provides a variety of layer styles—such as shadows, glows, and bevels—that change the appearance of a
layer. After Effects can preserve these layer styles when importing Photoshop layers. You can also apply layer styles in
After Effects and animate their properties.
You can copy and paste any layer style within After Effects, including layer styles imported into After Effects in PSD
files. Richard Harrington provides a video tutorial on the
Creative COW website that shows how to bring a library of
layer styles from Photoshop into After Effects so that you can use, modify, copy, and paste the custom layer styles in After
Effects.
In addition to the layer styles that add visual elements—like a drop shadow or a color overlay—each layer’s Layer Styles
property group contains a Blending Options property group. You can use the Blending Options settings for powerful
and flexible control over blending operations.
Though layer styles are referred to as effects in Photoshop, they behave more like blending modes in After Effects. Layer
styles follow transformations in the standard render order, whereas effects precede transformations. Another
difference is that each layer style blends directly with the underlying layers in the composition, whereas an effect is
rendered on the layer to which it’s applied, the result of which then interacts with the underlying layers as a whole.
When you import a Photoshop file that includes layers as a composition, you can retain editable layer styles or merge
layer styles into footage. When you import only one layer that includes layer styles, you can choose to ignore the layer
styles or merge layer styles into footage. At any time, you can convert merged layer styles into editable layer styles for
each After Effects layer based on a Photoshop footage item.
After Effects can preserve all layer styles in imported Photoshop files, but you can only add and modify some layer
styles and controls within After Effects.
Note: For details about each layer style and its properties, see Photoshop Help.
Layer styles that you can apply and edit in After Effects
Drop Shadow Adds a shadow that falls behind the layer.
Inner Shadow Adds a shadow that falls inside the contents of the layer, giving the layer a recessed appearance.
Outer Glow Adds a glow that emanates outward from the contents of the layer.
Inner Glow Adds a glow that emanates inward from the contents of the layer.
Bevel And Emboss Adds various combinations of highlights and shadows.