MACROMEDIA FLASH 8-FLASH, Use Manual, Page: 268 / 678

268 Creating Motion
Using mask layers
For spotlight effects and transitions, you can use a mask layer to create a hole through which
underlying layers are visible. A mask item can be a filled shape, a type object, an instance of a
graphic symbol, or a movie clip. You can group multiple layers together under a single mask
layer to create sophisticated effects.
To create dynamic effects, you can animate a mask layer. For a filled shape used as a mask, you
use shape tweening; for a type object, graphic instance, or movie clip, you use motion
tweening. When using a movie clip instance as a mask, you can animate the mask along a
motion path.
To create a mask layer, you place a mask item on the layer that you want to use as a mask.
Instead of having a fill or stroke, the mask item acts as a window that reveals the area of linked
layers that lie beneath it. The rest of the mask layer conceals everything except what shows
through the mask item. A mask layer can contain only one mask item. You cannot have a
mask layer inside a button, and you cannot apply a mask to another mask.
You can also use ActionScript to create a mask layer from a movie clip. A mask layer created
with ActionScript can be applied only to another movie clip. See “Using movie clips as masks”
in
Learning ActionScript 2.0 in Flash .
To create a mask layer:
1. Select or create a layer containing the objects to appear inside the mask.
2. With the layer selected, select Insert > Timeline > Layer to create a new layer above it.
A mask layer always masks the layer immediately below it, so be sure to create the mask
layer in the proper place.
3. Place a filled shape, text, or an instance of a symbol on the mask layer.
Flash ignores bitmaps, gradients, transparency, colors, and line styles in a mask layer. Any
filled area is completely transparent in the mask; any nonfilled area is opaque.
4. Right-click (Windows) or Control-click (Macintosh) the mask layer’s name in the
Timeline, and select Mask from the context menu.
The layer is converted to a mask layer, indicated by a mask layer icon. The layer
immediately below it is linked to the mask layer, and its contents show through the filled
area on the mask. The masked layer name is indented, and its icon changes to a masked
layer icon.
5.
To display the mask effect in Flash, lock the mask layer and the masked layer.