Applying a Matte to a Layer

If you have a video clip and a corresponding matte clip that was created separately from the video (not on the alpha channel), you can use the Set Matte effect to easily composite the clips over a back clip.

By linking the clips together, the matte layer acts as an alpha channel for the front video layer.

Set Matte differs from stencils in that the matte layer follows the front layer transforms. You cannot move these layers independently from one another.

Note: To follow this example, you must have previously digitized a back clip, a front video clip, and a corresponding matte layer clip.

To use an existing matte clip:

1. Choose File | Import Footage to import the back, front, and matte clips into a composite.

The file browser appears.

2. Load the appropriate files and click OK.

Note: Make sure the front and matte clips are synchronized (the first matte frame corresponds to the first front layer frame, and both sequences have the same total number of frames).

3. In the Workspace panel, adjust the layer stacking order so that the front layer is on top of the back layer. The matte layer should be turned off.

Since the matte layer does not need to be on, you could have opened the matte clip in the workspace (Footage Library) instead of importing it as a layer and then turning off the layer.

4. Select the Front layer.
5. Choose Operators | Channel | Set Matte.

The Set Matte Controls panel appears.



6. Click the Layer button.

The Operator Picker dialog appears.

7. Select the Footage operator under the Matte Layer and click OK.



8. From the Input Channel list, select Luminance.

A matte is applied to the clip. You can see the front layer applied over the back layer.