Setting Extrapolation Methods
Extrapolation is used to determine the behavior for a channel before the first or after the last keyframe. A dotted line appears in the Timeline to indicate where extrapolation is used.
Extrapolation is useful when you want to create a cyclical effect, such as a shutter flicker (as you would find in an old-time movie clip). You create one period in the flicker cycle, then use extrapolation to repeat the period over and over.
You see the effects of extrapolation only if your clip has frames before the first keyframe or after the last keyframe.
Types of extrapolation are described as follows.
(Mixed)Indicates that the selected keyframes contain a variety of extrapolation methods. Selecting this option does not change the existing extrapolation.
ConstantApplies the value at the first or last keyframe to all the frames that come before the first keyframe or after the last keyframe.
LinearContinues the curve in a linear fashion before the first keyframe or after the last keyframe.
LoopCycles the animation as it appears between the first and last keyframe.
Ping PongCycles the animation as it appears between the first and last keyframes forward then backward like a Ping-Pong ball bouncing back and forth across a Ping-Pong table.
Relative RepeatCycles the animation as it appears between the first and last keyframe, similarly to Loop extrapolation, but with a relative offset based on the channel value at the last keyframe.
To set extrapolation:
- In the Timeline controls, click the Graph button to switch to Graph mode.
- In the Timeline list, select the channel that you want to animate (if required, expand the categories in the Timeline list until the channel is visible).
The animation curve appears in the Timeline view.
- To set the animation behavior for frames before the first keyframe, select an extrapolation from the Extrapolation Before list.
- To set the animation behavior for frames after the last keyframe, select an extrapolation from the Extrapolation After list.