Creating Masks Within AE

To create a mask:

1. Select any layer, or create a new layer by pressing Cmd+Y (Ctrl+Y).

2. Click on the Pen Tool in the Tools Palette.

3. Click anywhere in the composition window to make a vertex point.

4. Continue clicking to add points.

5. Return to the first point you made to close the mask. You'll see a circle icon appear next to your Pen Tool to indicate you are closing the mask.