2011

Modifying Extrapolation
Extrapolation is used to determine the behavior of a channel before the first,
or after the last, keyframe. Extrapolation is useful when you want to create a
cyclical effect, such as shutter flicker (as you would find in an old-time movie).
You create one period in the flicker cycle, then use extrapolation to repeat
the period over and over again. You will see the effects of extrapolation only
if the film image has frames before the first keyframe or after the last keyframe.
The following extrapolation types are supported:
■ Constant Applies the value at the first or last keyframe to all the frames
that come before or after the last or first keyframe.
■ Linear Continues the curve in a linear fashion before the first keyframe
or after the last keyframe using the tangent.
■ Loop Cycles the animation as it appears between the first and last
keyframe.
■ Ping Pong Cycles the animation as it appears between the first and last
keyframes forward then backward.
■ Relative Cycles the animation as it appears between the first and last
keyframe. This is similar to “Loop”, but the relative offset is based on the
channel value derived from either the first or last keyframe.
■ Key Linear Continues the curve in a linear fashion before the first
keyframe or after the last keyframe, disregarding all tangents.
Temporarily Modifying Attribute Values
Even if an attribute is animated, you can temporarily modify its value to see
what the result would look like, without actually modifying the animation
data. You can do this by using the tool UI or by direct manipulation when
AutoKey is off. When you do so, the green or red bar across the top of the
value field in the tool UI turns yellow.
NOTE To acknowledge the change, you must set the keyframe either using the
keyframing controls with marked attributes or the context menu actions.
688 | Chapter 27 Animation