An example of using Additive Layers. Each layer stores its own animation data, and when they are enabled simultaneously,
this data is added together, forming a complete animation.

This feature allows you to separate an object’s motion into several ‘layers’ that are combined together when the animation is played.

To access it, select Animation Layers from the Window menu:

This will open the Animation Layers window:

This window contains a list of Layers.
By default, there’s only the Base layer, but you can add new ones.

Interface

Layers are controlled by a set of tools found at the bottom of the Additive Layers window:

(1) The ‘weight’ of the layer i.e. how much it influences the animation.
(2) Moves the currently selected layer up (doesn’t work with the base layer).
(3) Moves the currently selected layer down (also doesn’t work with the base layer).
(4) Merges all existing layers to the base layer.
(5) Renames the currently selected layer.
(6) Creates a new layer.
(7) Deletes the currently selected layer (the base layer cannot be deleted).

A Layer can be selected by clicking it.

Each Layer has a checkbox at the left side. Using this checkbox, you can disable or enable back the Layer and all its content (as shown in the image at the top of the page).

Using Additive Layers

Each Layer contains its own animation setup (consisting of keyframes and interpolations).
When the layer is enabled, this animation is added to the object’s base position/animation (stored on the base layer).

Every Keyframe or Interval you create is attributed to the currently selected Layer (by default, it is the Base layer).

This means that by switching between the layers, you can separate an animation into parts that are only combined when the animation is played.