To create a green screen mask in After Effects, use the Pen Tool to manually trace around your subject in your green screen footage.
Here's a step-by-step breakdown:
- Select your footage: In your After Effects composition, select the green screen footage layer that you want to mask.
- Choose the Pen Tool: Locate the Pen Tool icon in the top toolbar. It looks like a fountain pen tip. Click on it to activate it.
- Draw the Mask:
- Click around the edges of your subject to create points. These points will form the outline of your mask. Aim for accuracy, especially around fine details like hair.
- For curved edges, click and drag the Pen Tool to create Bezier handles. Adjust these handles to shape the curves of the mask.
- Continue clicking and dragging to define the entire outline of your subject.
- Close the Mask: Once you've traced the entire subject, click on the first point you created to close the mask. After Effects will automatically connect the last point to the first, completing the mask.
- Adjust the Mask:
- You can refine the mask by adjusting the position of the points and the Bezier handles.
- In the Layer panel, expand the properties of your footage layer. You should see a "Masks" section. Here, you can adjust the mask's Feather, Expansion, and Opacity to further refine the mask's appearance. Feather softens the edges, Expansion grows or shrinks the mask, and Opacity controls the mask's transparency.
- Mask Mode: Check the Mask Mode (usually set to "Add" by default). If you want to remove everything outside of your drawn selection, ensure it's set to Add. Otherwise you can subtract the mask ("Subtract"), intersect it with another mask ("Intersect") etc.
Important Considerations:
- Pre- or Post- Keying: You can create the mask before or after applying a keying effect like Keylight. Sometimes, masking first can isolate the area for the keying effect, making the keying process easier. Other times, applying the key and then masking allows you to clean up any remaining unwanted areas. Experiment to see what works best for your footage.
- Rotoscoping: For shots where the subject moves, you'll need to animate the mask over time. This process is called rotoscoping. You can use the mask path keyframes to track the subject's movement. Use the Current Time Indicator to move through your clip and adjust the mask for each point in time where your mask no longer fits the subject.
- Refine Edge Tool: After Effects also offers a Refine Edge tool, which can help improve the mask around tricky areas like hair. This tool analyzes the edges of the mask and automatically softens and smooths them.
By following these steps, you can create accurate and effective green screen masks in After Effects.
