Apple Shake 4 Tutorials - Manual (Page 152)

152 Tutorial 4 Working With Expressions
The solid alpha value is extended infinitely, and masks the RGrad outside of the
ceiling frame.
6 View RBlur1 (click the left side of the node).
The bleeding from the edges disappears.
Solution 2: Clip the Infinite Workspace
The second solution is to clip the Infinite Workspace with a Crop node. This removes
everything outside of the frame, and returns the frame to black.
To add a Crop node:
1 If you already followed Solution 1, delete the SetBGColor1 node and reconnect the
Viewport1 node to the Outside1 node.
2 Select the Outside1 node and insert a Transform–Crop node.