Editing Key Tangents

Command entry: Track View

Editing Keys in Curve Editor

Curves Toolbar

(Show Tangents)

By default, all key tangents are set to Auto and Show Tangents is on, so the tangents are drawn as blue dashed handles emanating from highlighted keys in the Key window of Track View. If the Move tool is active, you can adjust the shape of a function curve near the key by dragging the handle endpoints. For more information about tangents, see Tangent Types.

When you move the handle of an Auto tangent, the tangent type is automatically changed to Spline, as indicated by the color changing to black. You can change the tangent type for all highlighted keys at any time with the controls on the Key Tangents toolbar.

Spline Tangent

You can assign the Spline tangent type to any visible key in the Curve Editor. Highlight the key and then click the (Set Tangents to Spline) button on the Key Tangents: Track View toolbar to display the handle controls. Also, moving an Auto tangent handle automatically changes the type to Spline.

Tangent handles can be either continuous (unified) or discontinuous (broken).

Continuous handles move as a single lever with its pivot point at the key location. Moving either handle also moves the opposite end, maintaining the continuity of the tangent.
To make a key's handles continuous, highlight the key and click (Unify Tangents) on the Tangent Actions toolbar.
Discontinuous handles behave like leaves on a hinge, with the hinge pin at the key location. Each end moves independently of the other.
To make a key's handles discontinuous, highlight the key and click (Break Tangents) on the Tangent Actions toolbar, or hold down the Shift key when you move a handle.

Horizontal Bezier Handle Control

You can change the shape of the function curve around a key set to Spline tangent type by moving the tangent handle along its length. This affects the amount of influence the keyframe has over the interpolation between keyframes.

You can use this feature to aid in the slow-in and slow-out workflow of traditional animation. For example, suppose you're animating a ball bouncing up and down on the world’s Z axis. At frame 1, the ball is on the ground; at frame 8, the ball is in the air; and at frame 16 the ball is back on the ground. You could adjust the tangents for frame 8 so that their length pulls more of the curve towards its keyframe and away from the keyframes on frame 1 and 16. When rendered, the ball will be more visible on screen near the top of its bounce and blurrier near the points where it touches the ground.

Procedures

To assign a Spline tangent type:

Open the Curve Editor.
In the Hierarchy list, highlight one or more tracks that contain keys.
Highlight one or more keys on the curves.
On the Key Tangents: Track View toolbar, click (Set Tangents to Spline).
The handles are now all Spline and available for editing.

Tip If a highlighted key is set to Auto tangent, you can just move its handle to instantly convert the key to Spline tangent.

To edit the length of a Bezier handle:

Assign a Spline tangent type to the key you want to edit on the function curve, or highlight a key that already has one.
Make sure (Show Tangents) is on. This toggle is located on the Track View toolbar.
Highlight the key on the function curve.
Tangent handles appear on the highlighted keyframe.
Move one of the handles horizontally away from its key.

Interface

Show Tangents: Displays the tangents of highlighted vertices, whereupon you can adjust the tangents by dragging the handle endpoints.

By holding down the Shift key, you can edit the tangents handles separately.