Apple Shake 4 - Manual (Page 271)

Chapter 8 Using the Time View 271
In the following example, two clips have been added to the script.
Connecting both FileIn nodes to a Transition node (located in the Other tab) offsets the
second input clip from the first. Notice that the transition node appears underneath,
spanning the combined duration of both clips.
You can now route the combined output of the Transition node to as complicated a
node tree as you like, and both image nodes feeding the transition node will be treated
as a single image stream.
So, how is this different from just compositing the clips with an Over node and
offsetting the second clip in time? The advantage is that you can easily dial in an
overlap value to determine how many frames they overlap, and add a simple transition
effect. In the following screenshot, the overlap value is increased in the Transition node,
and the second node shifts to the left as it increases. You can also shift the second clip,
and read the overlap value in the Transition node.
Note: When the mixer parameter is set to cut, the cut point occurs at the beginning of
the second clip, not at the end of the first clip.
Parameters in the Transition Node
The Transition node has the following parameters:
overlap
This parameter sets the amount that the second clip is shifted earlier (to the left) to
provide overlap of the two clips.