The only good track matte is an animated track matte.
In the wonderful world of compositing, the track matte can be a confusing tool. This might be due to the fact that other compositing methods are much more straightforward.
Take masking as an example. A mask is exactly what it sounds like—it masks or hides part of a layer by simply making it transparent. You can use the pen or shape tools to easily mask out part of a layer, in turn revealing the underlying content. They're also quite easy to work with as they are applied to the layer you're masking. When you move or change any transform attributes of your layer, the mask will change along with the layer. Everything is neatly placed in a single location and works from the top down.
Chroma keying is another relatively simple compositing method. When you apply a chroma key effect to a layer, you’re basically telling the effect to make the layer transparent at specific color values. In most cases, you’re using either a green or blue screen. Once the chroma key effect is applied, those specific color values will be transparent, revealing the layers below. Once again, this is easy and simple to execute. Track mattes, on the other hand, are less so.
When using a track matte, you are transferring the transparency information of one layer and assigning it to another. Because of this, it requires at least two layers to achieve. As an example, take a look at the still images below.
This simple composite consists of two layers—the track matte and the source clip. The track matte is a simple white circle with a transparent background. Everything you see in black is transparent.
Once I apply this as a track matte to my source clip, we'll only see what's in the white circle. Everything else will be transparent. So how can we use this circular track matte as a transition? Simple—animate it.
Take a look at the new Prism transition pack from Rocketstock. This pack includes 200 different transitions in 9 different categories, including 30 circle transitions. All of these transition clips are simple animated shapes with alpha channels that animate in and move to cover the entire screen at some point. Covering the entire screen allows for a perfect transition between two clips.
Let's take a step-by-step look at how we can use one of these mattes to transition between two clips in Adobe Premiere Pro.
1. Find two clips that you want to transition between
I’ll place my second clip over the first, right around the point where I want to transition between the two.
2. Put your track matte clip onto the video track
Next, I’ll grab my track matte clip from the project panel and place it on video track 3, perfectly aligned with my second shot.
3. Use the Track Matte Key
For the secret sauce, I’ll go into the Effects panel and grab the Track Matte Key. To apply it, I’ll drag and drop onto my second shot on video track 2.
4. Put the Effect Controls panel to good use
Finally, I’ll select the second shot and open up the Effect Controls panel. Now all I have to do to get the transition working is specify video track 3 for the matte. Voila! Our transition is complete!
Have you ever used a track matte as a transition? Let us know in the comment section down below.