Masks

Masks

Masks are the principal non-procedural method to defi ne
transparency in a layer; they are vector shapes that you
draw by hand. There are fi ve basic shapes (the Q key cycles
through them) and the Pen tool (G) for drawing free-form.
A mask can be drawn in either the Composition or Layer
viewer. In Layer view the source image persists in its default
view; there is a Render toggle next to the Masks selection
in the View menu to disable all mask selections. Artists may
want to see a masked layer in the context of the comp but
fi nd it diffi cult to adjust the mask in that view—in such a
case, the Layer and Composition views can be arranged
side-by-side

When using a Mask Shape tool
. Double-click the tool (in the Tools palette) to set the
boundaries of the mask shape to match those of the
layer.
. Press Shift to constrain proportions when drawing or
scaling.
. Use Ctrl/Cmd to draw from the center (with the Rectangle,
Rounded Rectangle, and Ellipse tools).

. Click Shape under Mask Path (M) in the Layer Switches
column to open the Mask Shape dialog; here you can
enter exact mask dimensions.
. Double-click the shape with the Selection tool to activate
Free Transform mode, then
. Shift-drag on corner to scale the mask
proportionally.
. Shift-drag outside corner to snap rotation to
45-degree increments.
. Shift-drag anywhere else to transform on one axis
only.
. Press the M key twice, rapidly, to reveal all Mask options
for the selected layer.
. Press the F key to solo the Mask Feather property.
Feather is applied everywhere equally on the mask,
equidistant inward and outward from the mask shape.
. Use Mask Expansion to expand or (given a negative
value) contract the mask area. Two masks can be used
together, one contracted, one expanded, to create an
edge selection.
Chapter 7 has more information about drawing precise
masks; big, soft masks are referenced throughout the
book for all kinds of lighting, smoke, and glow effects