Adobe 65008009 - After Effects CS4 Using Manual page 71

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Last updated 12/21/2009 USING AFTER EFFECTS CS4
Projects and compositions
Transformations are changes to those properties grouped under the Transform category in the Timeline panel,
including Anchor Point, Position, Scale, Rotation, and Opacity. What you see in the Layer panel is the result of the
rendering before transformations are performed.
Note: For additional control over when transformations are performed, you can apply the Transform effect and reorder
it with respect to other effects.
In a group of effects or masks, items are processed from top to bottom. For example, if you apply the Circle effect and
then apply the Magnify effect, the circle is magnified. However, if you drag the Magnify effect above (before) the Circle
effect in the Effect Controls or Timeline panel, the circle is drawn after the magnification and isn't magnified.
After a layer has been rendered, rendering begins for the next layer. The rendered layer below may be used as input to
the rendering of the layer above—for example, for determining the result of a blending mode.
If a composition contains other compositions nested within it, the nested composition is rendered before other layers
in the containing composition.
Note: Some effects ignore masks on the layer to which they're applied. To have such an effect operate on a masked layer,
pre-compose the layer with the mask applied, and then apply the effect to the pre-composed layer. (See "About
precomposing and nesting" on page 60.)
Collapsing transformations
If the Collapse Transformations switch is selected for a nested composition, then the transformations for the nested
composition are not performed until after the masks and effects for the containing composition are rendered. This
render order allows the transformations for the nested composition and the containing composition to be combined—
or collapsed—and performed together. The same is true for vector layers that are not continuously rasterized.
Note: Instead of a Collapse Transformations switch, vector layers have a Continuously Rasterize switch in the same
location. Vector layers include shape layers, text layers, and layers with vector graphic files as the source footage. Text
layers and shape layers are always continuously rasterized.
Collapsing transformations can, for example, preserve resolution when a layer is scaled down by half in a nested
composition, and the nested composition is scaled up by a factor of two in the containing composition. In this case,
rather than performing both transformations and losing image data in the process, one transformation can be
performed—doing nothing, because the individual transformations cancel each other.
If transformations are not collapsed, a nested composition that contains 3D layers is rendered as a 2D image of the 3D
arrangement, using the default composition camera. This rendering prevents the nested composition from
intersecting with 3D layers, casting shadows on 3D layers, and receiving shadows from 3D layers in the containing
composition. The nested composition is also not controlled by the cameras and lights of the containing composition.
If transformations are collapsed, the 3D properties of the layers in the nested composition are exposed to the
containing composition. Thus, the nested composition can intersect with 3D layers, cast shadows on 3D layers, and
receive shadows from 3D layers in the containing composition. The containing composition's camera and lights can
also control the nested composition.
Essentially, collapsing transformations for a nested composition tells After Effects to not flatten and crop the layers in
the precomposition. Because an adjustment layer operates on the composite of all of the layers beneath it within the
same composition, an adjustment layer within a nested composition with collapsed transformations will force the
flattening and cropping that collapsing transformations would normally prevent.