Apple Shake 4 - Manual (Page 533)

Chapter 19 Using Masks 533
Masking Concatenating Nodes
It is never a good idea to use side input masking with multiple successive
concatenating nodes because doing so breaks the concatenation. The following
example demonstrates the wrong way to use masks.
Breaking node concatenation with side input masks—don’t try this at home:
1 Select the Brightness node and apply a Color–Mult node.
2 In the Color controls of the Mult node parameters, set the Color to blue.
A blue tint is created to color correct the dark areas of the background.
3 Connect the output of the CornerPin node to the M input of the Mult node.
4 To invert the mask on the Mult node, expand the Mask controls and enable invertMask.
The Mult (color-correction) node is masked and the mask is inverted (like the Brightness
node), so that only the dark areas are tinted blue.
5 In the Mult node, adjust the Color controls to a deeper blue color.
Although the result appears fine, there are several problems with the above approach:
• Normally, the Mult and Brightness functions concatenate. By masking either node,
you break concatenation. When concatenation is broken, processing time slows and
accuracy decreases.
• Masking twice with the same node (the RGrad node in this example) slows
processing.
• Your edges get multiple corrections, and tend to degrade. This is evident by the blue
ring around the soft parts of the mask.