Ever found yourself needing boundaries? We don't mean rules or a schedule to follow, but rather graphical walls to contain an element. Perhaps you want to take footage of an ocean and have it show through letters , or you want the shape of a client's logo to contain a data stream. That's what track mattes are for.
Be sure that you see modes in your timeline (if not click the Switches/Modes button at the bottom of the window).
Position the two layers in your timeline so the matte layer (the one that cuts) is directly above the fill layer. Be sure there are no gaps between the fill and matte layers .
In the TrkMat drop down menu, pick one of the following methods to define transparency.
Alpha Matte. Areas with 100 percent alpha channel are opaque .
Alpha Inverted Matte. Areas with 0 percent alpha channel are opaque.
Luma Matte. Areas with 100 percent luminance pixels are opaque.
Luma Inverted Matte. Areas with 100 percent luminance pixels are opaque.
When the track matte feature is turned on, the matte layer's visibility is disabled. You can turn it back on, but that usually defeats the purpose. You still have the ability to manipulate and resize the layer, and its transformations will carry through to the matte.