Apple Shake 4 Tutorials - Manual (Page 136)

136 Tutorial 4 Working With Expressions
5 Toggle the clipMode parameter of Over2 to set the resolution to foreground.
The image should now look like this:
Creating a Light Source With RGrad
Since you have only five frames of material, you can add a little kick to the composite
by animating the position of the RGrad gradient shape to simulate a moving spotlight.
To animate the RGrad node:
1 Go to frame 1.
2 Click the left side of the Over2 node to load it into the Viewer, then click the right side
of the RGrad1 node to load its parameters.
The RGrad1 onscreen controls appear. You might need to zoom out a bit; move the
pointer over the Viewer and press the minus key (–) a few times.
3 In the Viewer, turn on Autokey.
A position keyframe for the RGrad gradient shape is created.