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Chapter 12 Using Shapes and Masks 857
Feather: A slider that feathers (softens) the edges of a mask. Positive feathering values
soften the edge of the mask from its edge outward. Negative feathering values soften
the edge of a mask inward from the edge. Feathering the edge of a mask can soften a
harsh rotoscoping job, making the masked object blend more easily with the
background.
Combining Multiple Masks
Often, you may find that it is impossible to create the mask shape you need using only
a single mask. For example, when masking something that has a hole in it, you need to
use at least two masks—one set to Add to mask the overall object, and a second one
set to Subtract to cut the necessary hole in the middle of it. In the following example,
the only way to mask the space between the diver’s arms and legs is to create three
overlapping masks set to Subtract.
Other times, you may find that it’s simply more convenient to mask a complex object
using multiple masks. This is frequently the case when rotoscoping an object and
animating the masks. In this example, the dog’s head is masked with four different
masks set to Add—one for the head, one for each ear, and a separate mask for the
mouth. This makes it easier to make adjustments later on, especially when animating a
mask to do rotoscoping.
Original object
Three overlapping masks
Final result
Original object Four overlapping masks End result
01112.book Page 857 Sunday, March 13, 2005 10:36 PM