In After Effects, clipping masks are achieved using track mattes. This isn't called a "clipping mask" directly within the software, but it performs the same function. Instead of a clipping mask, you'll use a layer as a matte for another.
Understanding Track Mattes
A track matte uses one layer (the matte layer) to control the visibility of another layer (the source layer). Only the portions of the source layer that are visible within the matte layer will be shown in the composition. This effectively masks the source layer to the shape of the matte layer.
Steps to Create a Track Matte (Clipping Mask):
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Layer Order: Ensure your layers are stacked correctly. The layer you want to act as the mask (e.g., a circle shape) should be below the layer you want to be masked (e.g., an image).
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Select the "Take Matte" Option: In the Timeline panel, locate the layer you want to be masked. Look for the "Take Matte" or similar option in the layer's attributes. This is where you select the layer below it, which will serve as its track matte.
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Choosing Alpha or Luma Matte: You'll then select "Alpha Matte" or "Luma Matte" within the "Take Matte" settings.
- Alpha Matte: Uses the transparency of the matte layer to control visibility. Fully transparent areas of the matte layer will make the corresponding areas of the source layer invisible.
- Luma Matte: Uses the brightness values of the matte layer. Bright areas will show the source layer; dark areas will hide it.
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Animation: Both the shape of the matte layer and the position of the layers can be animated to create dynamic and complex effects. You can animate the shape using keyframes to create the reveal and hide effect.
Example:
Let's say you have a star-shaped layer and a circular layer. To clip the star to the circle:
- Place the circular layer below the star layer.
- Select the star layer.
- Select the circular layer in the "Take Matte" option. Choose "Alpha Matte" for simple masking based on transparency.
Different Approaches & Considerations:
- Shape Layers: Shape layers are ideal for creating precise matte shapes. Use the various shape tools within After Effects to create your mask.
- Importing Masks: You can import files from Photoshop with pre-existing masks. However, you will still need to use the track matte feature in After Effects to utilize the mask correctly. Remember that the mask information will be interpreted as an alpha channel in After Effects.
