Adobe After Effects CS4 - Manual (Page 174)

168 USING AFTER EFFECTS CS4
Layers and properties
Last updated 12/21/2009
A composition can contain any number of null objects. A null object is visible only in the Composition and Layer
panels and appears in the Composition panel as a rectangular outline with layer handles. Effects are not visible on null
objects.
❖ To create a null object, select the Timeline or Composition panel and choose Layer > New > Null Object.
Note: The anchor point of a new null object layer appears in the upper-left corner of the layer, and the layer is anchored
in the center of the composition at its anchor point. Change the anchor point as you would for any other layer.
If a null object is visually distracting in your composition frame, consider dragging it out of the frame, onto the
pasteboard.
Guy Chen provides a simple project on the After Effects Exchange on the Adobe website that demonstrates the
animation of several 3D layers arranged as a cube, controlled by a parent null layer.
Angie Taylor provides an extensive discussion and explanation of animation using parenting, expressions, and null
object layers in a PDF excerpt from her book
Creative After Effects 7: Workflow Techniques for Animation, Visual
Effects, and Motion Graphics .
More Help topics
“ Expression Controls effects ” on page 653
“ Layer anchor points ” on page 162
Guide layers
You can create guide layers from existing layers to use for reference in the Composition panel, to help you position and
edit elements. For example, you can use guide layers for visual reference, for audio timing, for timecode reference, or
for storing comments to yourself.
A guide layer icon appears next to the name of a guide layer or its source in the Timeline panel.
By default, guide layers aren’t rendered when you create output but can be rendered when desired by changing the
render settings for the composition.
Note: Guide layers in nested compositions can’t be viewed in the containing composition.
• To convert selected layers to guide layers, choose Layer > Guide Layer.
• To render a composition with its visible guide layers, click Render Settings in the Render Queue panel, and choose
Current Settings from the Guide Layers menu in the Render Settings dialog box.
• To render a composition without rendering guide layers, click Render Settings in the Render Queue panel, and
choose All Off from the Guide Layers menu in the Render Settings dialog box.
More Help topics
“ Render settings ” on page 697
Use Brainstorm to experiment and explore settings
Brainstorm creates multiple temporary variants of your composition and displays them in a grid. You can save any
number of these variants, apply one to the current composition, or redo the Brainstorm operation using only the
variants that you choose as input.
Brainstorm uses genetic algorithms to mutate and select property values used as input into each Brainstorm operation.
You decide which variants to include as input to each generation and how much mutation (randomness) to use.