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The Beginner’s Guide to Using Alpha Mattes in After Effects


Want to reveal text or assets in an inventive way? Here’s a simple way to use alpha mattes to make that title sequence pop.

So, like me, you may want to create your own graphics for your film so you don’t have to outsource it to someone else. Maybe you have an idea how you want your film to look creatively, but you don’t have much experience in After Effects. What we are going to do here is create a title sequence using an Alpha Matte. All you need is two layers, and the asset or title you want to reveal. For this example, we are going to use a boxing glove that is going to punch through the side of the screen to reveal the title underneath.

First, what we are going to do is open up After Effects CC. Click Composition > New Composition. In the pop-up box; make sure you select HDTV 1080 24 as your preset so you can directly import this to your timeline in Premiere without any scaling issues.

The Beginner's Guide to Using Alpha Mattes in After Effects — New Composition

Feel free to change your background color, but you can keep it white right now so we can see the background clearly while we build this animation. You can always change it later under Composition > Composition Settings.

So now we are going to create a text layer that we are going to reveal with the Alpha Matte. For this example, we are just going to use a text layer, but I highly recommend building a title in Photoshop so you can adjust it to your liking. Click Layer > Text to create a new text layer.

The Beginner's Guide to Using Alpha Mattes in After Effects — New Text Layer

Now to keep things simple, we are just going to use a black foreground. Let’s go ahead and create a new layer by clicking Layer > New > Solid. The black layer is going to cover up our text, but not to worry: we are going to reveal it later with the Alpha Matte.

The Beginner's Guide to Using Alpha Mattes in After Effects — New Solid

Since we are creating this for a fighting film, we are going to add in a boxing glove that’s going to reveal the text underneath the foreground. Download a PNG of a boxing glove and import it in to After Effects using File > Import.

The Beginner's Guide to Using Alpha Mattes in After Effects — Add Element

Now that we have our proverbial table set, let’s get to the cool stuff. You will find a drop-down menu to the right of your layers in the timeline window labeled TrkMat. (If you cannot find this drop-down menu, go to the very bottom left of the program, and select the circle and square icon to expand your options.) On the black solid layer, click that drop-down menu and select Alpha Inverted Matte. For this to work, your glove layer must be one above the black solid layer in your timeline.

The Beginner's Guide to Using Alpha Mattes in After Effects — Alpha Inverted Matte

Voilà! There’s your text under an outline of the boxing glove. You will notice that if you move around the layer, the background will only appear through the cutout of the glove. If you want to maintain the outlines of the boxing glove while still revealing your text, you can also use a Luma Inverted Matte. You can find that in the same drop-down menu where you found the Alpha Inverted Matte. It’s going to look something like this:

The Beginner's Guide to Using Alpha Mattes in After Effects — Luma Inverted Matte

For this example, we are going to use the Luma Inverted, mainly because I love how the text works with the shading of the glove.

Now that we have the matte in place, let’s bring in some motion to make it more exciting. Click the drop-down arrow next to the glove layer and click Transform. Click the stopwatch next to the Position tab to start your keyframe tracking. Make sure your timeline play head is at 0:00 so it begins tracking from the very beginning.

Let’s move the boxing glove off screen to the left. Just so you don’t lose your glove layer, minimize your composition size so you can still manipulate items outside of the actual composition window. Remember, the playhead should still be at 0:00.

Now, move the playhead over about half a second. After that, move the boxing glove layer over the text. It will automatically create a keyframe that will fill in the gaps for you with motion. Now with the motion in place, you will get to see the coolest part about the Alpha Matte: the text appears through the glove.

The Beginner's Guide to Using Alpha Mattes in After Effects — Text Reveal

Congratulations! You have now successfully crafted an animated title sequence using a matte. Remember: these are the bare essentials for creating a composition using the Alpha and Luma mattes. When you get more comfortable with After Effects, feel free to create more complex motion to reveal the background assets, or even use a video as your foreground to make it more visually pleasing.