In this article we are going to create a popular effect of playing video through text.
This is called creating a track matte or a traveling matte. Watch prime time television and you will see this technique used in commercials and show openings. This a common task asked of Motion Graphics Artists, and a basic recipe that you will use to quickly create visual interest. We also talk about Nesting, which is a building block in creating complex After Effects projects.
Import a video clip into After Effects by double-clicking in the Project Panel.
Create a New Composition that matches your footage by dragging the clip onto the new Composition icon at the bottom of the Project panel. (The Composition will be named the same as the clip, so click on the clip and hit Return to rename it.)
Step 3 - Create Text
Create Text by going to Layer > New > Text, or by selecting the Text tool and clicking in the Composition and then type your word. In the Character Panel change the font to a large meaty font (I used Arial Black).
*For a refresher on working with text read this*
In the Timeline Panel, make sure the text layer is above the video layer.
Select the video layer and change the 'TrkMat' pulldown from None to Alpha Matte 'music' (the name will be the layer on top. The track matte looks at the layer above). The video is now inside the text layer and the background is black.The eye will disappear for the text layer, and a icon appears telling you that the text is now acting as a matte.
In the Composition panel, click 'toggle transparency' to see the checkerboard pattern (this shows that the video clip only appears inside the text and the rest of the Composition is transparent).
To add a drop shadow or other effect, we need for the 2 layers to act as one layer. To do this we put this comp into another, which is called nesting. Drag the 'track matte' comp onto the new Composition icon at the bottom of the Project panel (we did this with a clip in Step 2). When you put a comp inside another comp, it acts as a layer. In the Project tab rename 'track matte 2' 'Master'.
The power in this technique is that the 2 layers are not flattened, but are still separate layers that can be changed. If your client wants to change the text or video layer later, the changes will ripple through to the Master composition.
In the effects/presets panel type "drop shadow".
Make sure the Track Matte layer is selected, and double-click on the drop shadow effect (this applies the effect, and is easier than dragging the effect onto the layer).
Note that we are applying the effect to the comp, and not to the individual layers inside the track matte comp. Experiment with other effects 'bevel alpha and glow' (help with readability).
We can now put another video clip underneath our track matte layer.
You could use the same clip and or another clip, depending on the look you want.
The beauty of this technique is that it is easy to build, but looks like you spent more time than you did. I find this works well in a pinch when the client wants to quickly spice up the text.