Creating track mattes and traveling mattes

When you want one layer to show through a hole in another layer, set up a track matte. You'll need two layers--one to act as a matte, and another to fill the hole in the matte. You can animate either the track matte layer or the fill layer. When you animate the track matte layer, you create a traveling matte. If you want to animate the track matte and fill layers using identical settings, consider precomposing them. (See Understanding precomposing.)

After Effects preserves the order of a layer and its track matte after you duplicate or split the layer. Within the duplicated or split layers, the track matte layer remains on top of the fill layer. For example, if your project contains layers A and B, where A is the track matte and B the fill layer, duplicating or splitting both of these layers results in the layer order ABAB. (See Duplicating a layer and Creating new layers by splitting a layer.)


Traveling Matte A. Matte layer (top) and fill layer (below) B. Animation of the matte layer's Scale property.

Related Subtopics:

Using alpha channel or luminance values for a track matte
Preserving underlying transparency during compositing