Working With Masks And Transparency - Adobe AFTER EFFECTS 5.5 Help Manual

Adobe After Effects Help
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Creating visible lines and solid shapes from masks
To outline or fill a mask, apply the Stroke (outline) and/or the Fill effect. Each mask in a
layer can have different fill and stoke settings. You can apply an outline to an open or
closed mask path, but if you want to fill a mask, it must be a closed path. See "Working
with effects" on page 170 for information on using effects.
Controlling how masks in the same layer interact
Transfer modes for masks control how different masks within a layer interact with one
another. By default, all masks are set to Add, which combines the transparency values of
any masks that overlap on the same layer. You can apply one mode to each mask, but you
cannot change a mask's mode over time.
The first mask you create interacts with the layer's alpha channel. If that channel doesn't
define the entire image as opaque, then the mask interacts with the layer frame. Each
additional mask you create interacts with masks located above it in the Timeline window
outline. The results of mask modes vary depending on the modes set for the masks higher
up in the outline. You can use mask modes only between masks in the same layer. For
more information on working with mask modes, see "Using mask modes" on page 162.
Using mask modes
Using mask modes, you can create complex mask shapes with multiple transparent areas.
For example, you can set a mask mode that combines two masks and sets the opaque area
to the areas where the two masks intersect.
A
D
Mask shapes that result when different modes are applied to circle mask:
A. Original masks B. None C. Add D. Subtract E. Intersect F. Difference
The following mask mode descriptions are based on interactions between two layer
masks—the top set to Add, the other set to the mask mode described:
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Working with Masks and Transparency

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