How Do I Add Two Masks in After Effects?

Adding or merging masks in After Effects isn't a direct "add" function, but rather involves combining their shapes. The most common method involves using Illustrator as an intermediary for precise merging, though After Effects also provides some built-in options for creating the appearance of combining masks. Here's a breakdown of the approaches:

Method 1: Using Illustrator for Precise Mask Merging

This method is best for completely joining two masks into a single, continuous shape.

1. Copy Masks: In After Effects, select the layer containing the masks you want to combine. Highlight and copy all the masks (Ctrl+C or Cmd+C).
2. Paste into Illustrator: Open Adobe Illustrator and create a new document. Paste the copied masks into the document (Ctrl+V or Cmd+V).
3. Direct Selection Tool: Use the "Direct Selection" tool (white arrow) in Illustrator.
4. Connect Endpoints: Select the endpoint of one mask, hold down the Shift key, and then select the endpoint of the other mask you want to join.
5. Join Paths: Press Ctrl+J (or Cmd+J on Mac) to join the selected endpoints. This creates a single continuous path.
6. Repeat: Repeat steps 4 and 5 as necessary until you have only one path representing the combined mask shape.
7. Copy Combined Path: Select the newly created combined path and copy it (Ctrl+C or Cmd+C).
8. Paste into After Effects: Go back to After Effects, select the layer you were working on, and paste the combined path into the Mask Path property of a mask (Ctrl+V or Cmd+V). This will replace the original masks with the single, combined mask. You can then delete the old masks if desired.

Method 2: Mask Modes in After Effects (For Visual Combination)

This method doesn't actually merge the masks into one shape but creates the effect of doing so by using mask modes. This is useful when you need to maintain the original masks as separate entities but want them to interact visually.

1. Create Masks: Create the two masks on the same layer in After Effects.
2. Set Mask Mode: In the Timeline panel, locate the "Mask Mode" column (you may need to expand the layer properties to see it). By default, the Mask Mode is set to "Add".
3. Experiment with Modes: Click on the Mask Mode dropdown for the second mask (and any subsequent masks). Experiment with different mask modes like:
   • Add: The masks' shapes are combined. Where they overlap, the area is filled.
   • Subtract: The second mask cuts out from the first.
   • Intersect: Only the area where the masks overlap is visible.
   • Lighten: The brighter values of the masks are combined.
   • Darken: The darker values of the masks are combined.
   • Difference: The areas where the masks differ are visible.

The best mode will depend on the visual result you're aiming for. Adjust the position and shape of the masks to fine-tune the combined effect. Note that the order of the masks in the timeline is significant with some modes, especially Subtract.

Choosing the Right Method

• Illustrator Method: Use this if you need a single, unified mask shape where the outlines are truly connected. It's best for complex shapes and requires Illustrator.
• Mask Modes Method: Use this if you want to visually combine masks without permanently merging them. It offers flexibility to adjust individual masks later and doesn't require Illustrator.