Apple Shake 4 - Manual (Page 904)

904 Chapter 29 Optimizing and Troubleshooting Your Scripts
Don’t Apply the Same Mask to Multiple Successive Nodes
Even if the nodes do not normally concatenate, but appear one after the other along
the same branch of the node tree, you get cleaner edges with the use of a KeyMix
node. In the example below, a circular mask is applied to three filter effects. Each filter
works on the previous node, so problems appear on the edges. The solution is again to
use a KeyMix node. This yields a faster render (does not mix the mask multiple times)
and a clean edge.
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