Adobe After Effects CS4 Manual de usuario descargar pdf (Pagina 66)

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101

USING AFTER EFFECTS CS4

Projects and compositions

Last updated 12/21/2009

Precomposing, nesting, and pre-rendering

About precomposing and nesting

If you want to group some layers that are already in a composition, you can precompose those layers. Precomposing

layers places them in a new composition, which replaces the layers in the original composition. The new nested

composition becomes the source for a single layer in the original composition. The new composition appears in the

Project panel and is available for rendering or use in any other composition. You can nest compositions by adding an

existing composition to another composition, just as you would add any other footage item to a composition.

Precomposing a single layer is useful for adding transform properties to a layer and influencing the order in which

elements of a composition are rendered.

Nesting is the inclusion of one composition within another. The nested composition appears as a layer in the

containing composition.

A nested composition is sometimes called a precomposition, which is occasionally abbreviated in casual use to precomp

or pre-comp. When a precomposition is used as the source footage item for a layer, the layer is called a precomposition

layer.

During rendering, the image data and other information can be said to flow from each nested composition into the

composition that contains it. For this reason, nested compositions are sometimes referred to as being upstream of the

compositions that contain them, and the containing compositions are said to be downstream of the nested

compositions that they contain. A set of compositions connected through nesting is called a composition network. You

can navigate within a composition network using the Composition Navigator and Mini-Flowchart. (See

“Opening and

navigating nested compositions” on page 62.)

Precompositions in After Effects are similar to Smart Objects in Adobe Photoshop.

More Help topics

“Precompose layers” on page 61

“Create layers from footage items or change layer source” on page 139

“3D layer interactions, render order, and collapsed transformations” on page 184

“Layer switches and columns in the Timeline panel” on page 154

“Parent and child layers” on page 166

Uses for precomposing and nesting

Precomposing and nesting are useful for managing and organizing complex compositions. By precomposing and

nesting, you can do the following:

Apply complex changes to an entire composition You can create a composition that contains multiple layers, nest the

composition within the overall composition, and animate and apply effects to the nested composition so that all of the

layers change in the same ways over the same time period.

Reuse anything you build You can build an animation in its own composition and then drag that composition into

other compositions as many times as you want.

Update in one step When you make changes to a nested composition, those changes affect every composition in

which it is used, just like changes made to a source footage item affect every composition in which it is used.

Alter the default rendering order of a layer You can specify that After Effects render a transformation (such as

rotation) before rendering effects, so that the effect applies to the rotated footage.

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Adobe After Effects CS4 Manual de usuario Pagina 66

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