Apple Shake 4 - Manual (Page 781)

Chapter 26 Transformations, Motion Blur, and AutoAlign 781
Note: To create a cloned node, copy the node (press Command-C or Control-C) and
clone the node using the Paste Linked command in the Node View shortcut menu (or
press Command-Shift-V or Control-Shift-V).
Because the SpinWheel and MoveCar1 nodes are transformations, these nodes
concatenate. The SpinWheel, PositionFrontWheel, and MoveCar2 nodes also concatenate.
The result is three transformations, the same amount as the previous tree, but with an
accurate blur on the wheels.
Applying Motion Blur to Non-Keyframed Motion
Ordinarily, motion blur only appears when you keyframe a parameter of a transform
node in order to create Shake-generated motion. If you simply read in an image
sequence with a moving subject within the frame, such as a man running along a road,
Shake will not create any motion blur, since nothing is actually animated.
To create motion blur for such non-keyframed elements, you can apply a smear effect
using a Move2D node. This is done by turning on the useReference parameter (at the
bottom of the Parameters tab) and setting referenceFrame (in the useReference
subtree) to “time” (the default).