To track a mask in After Effects, you essentially tell After Effects to follow a specific object or area in your video with a mask you've created. Here's how to do it:
Steps to Track a Mask:
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Create a Mask: Draw a mask on the layer you want to track. You can use the Pen tool (G) or shape tools to create the mask. Make sure the mask is roughly outlining the area you want to track.
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Select the Mask: In the Timeline panel, select the mask you want to track. You'll find masks listed under the layer they're applied to.
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Open the Tracker Panel: If the Tracker panel isn't visible, go to
Window > Tracker. -
Choose Mask Tracking Option: With the mask selected, the Tracker panel will automatically switch to mask tracking mode. You will see options related to tracking the mask:
- Method: Options typically include "Position", "Position, Scale, and Rotation", or "Perspective". Choose the method that best suits the movement of the object you are tracking. If the object only moves, "Position" is fine. If it also changes size and rotates, use "Position, Scale, and Rotation." If the object changes its angle relative to the camera, try "Perspective."
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Select Track Point: After Effects will analyze the mask and, depending on the "Method" chosen, create one or more track points within the mask. These are the points After Effects will try to follow.
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Adjust Track Point (if needed): You can adjust the position and size of the track points to target a distinct feature within the mask. For example, if tracking a face, position the track point on the eye or nose.
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Analyze Forward (or Backward):
- Click the "Analyze Forward" button (either one frame at a time or until the end of the layer) in the Tracker panel. After Effects will track the selected mask forward in time. You can also analyze backward if needed.
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Fix Tracking Errors: While After Effects does a good job, sometimes the tracker might lose the object it's tracking. When this occurs, you'll need to manually adjust the mask and/or the track points, and then resume tracking. You can also refine the initial track points and try again.
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Apply the Tracked Data: The mask path will now be animated to follow the movement you tracked. You can then use this mask for various purposes, like isolating an object, applying effects to a specific area, or creating composites.
Tips for Better Mask Tracking:
- Good Contrast: Track points work best when there is high contrast in the area being tracked.
- Distinct Features: Choose distinct, well-defined features to track.
- Adjust Search Size: Adjust the "Search Size" in the Tracker panel. A smaller search size is faster but less accurate, while a larger search size is slower but can be more accurate for objects that move quickly.
- Planar Tracking (Mocha AE): For more complex tracking scenarios, consider using the Mocha AE plugin that comes bundled with After Effects. Mocha AE provides planar tracking, which is more robust for tracking objects that go off-screen or undergo significant changes in perspective. You can send a layer to Mocha AE from within After Effects using
Animation > Track in Mocha AE.
By following these steps, you can effectively track masks in After Effects and enhance your video editing projects.
