Mask Layers
For spotlight effects and transitions, we can use a mask layer to create a mask 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.
A mask layer always masks the layer immediately below it.
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.
3. Place a filled shape, text, or an instance of a symbol on the mask layer.
4. Right-click the mask layer’s name in the Timeline, and select Mask from the context menu.
5. The layer immediately below it is linked to the mask layer, and its contents show through the filled area on the mask.
6. To display the mask effect in Flash, lock the mask layer and the masked layer.
