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8.1 Mattes

Mattes are a powerful tool to control what is being shown on a layer. In this lesson, you will learn about the alpha and luma mattes in After Effects and see how you might use them!

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2.Getting Started
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What Is After Effects?

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After Effects Tools

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FAQ Conclusion

8.1 Mattes

In this lesson you're gonna learn about alpha and luma mattes and see an example of how each are used. To follow along in this lesson make sure to open up the Mattes.aep file. It'll give you a project that looks something like this. You won't have all of the assets like this video clip here, this video clip here and this ink folder with all these fantastic ink elements. We can find all of those Envato elements. So let's talk about what mattes are. Matte is an abbreviation for track matte, and that's when you use another layer to drive your target layer's Opacity. I'm gonna jump into the alpha mattes composition here and let me walk you through what I have going on. At the bottom of the layer stack I have a green solid. I'll just solo that out there as you can see it's nothing special, just a really bright green solid. Above there I have a layer named Pattern and this is a solid layer with a couple of effects applied to it. I have a fractal noise effect, and a colorama effect, and that's what generating this pattern here. However, the layer that's directly above that is what this pattern layer is using for its transparency. So this pattern layer is getting all of its transparency information from the layer directly above it and that's because it's set to Alpha Matte. If I set this to no matte, you can see that it looks different. This is what the layer actually looks like. But when I apply a track matte and set this to alpha matte, it's going to be using the alpha information, which is the transparency of the layer to drive its transparency. Let's take a look at this matte layer right here. I'm gonna solo this matte layer here. I'm also gonna draw your attention to this info panel right up here, if you haven't checked that up before, go ahead and open that up. And you'll notice right here we have a little column R,G,B, and A. This stands for red, green, blue and alpha. The alpha channel is that pixel's transparency. And if you hover your mouse over your composition, you'll see that those numbers will dance all over the place. The thing that I want you to look for right now, is check out the alpha channel. So as I hover my mouse over this rectangle, you'll see the alpha channel is reading 255 and that's because right now this project has a bit-depth of 8-bits. Each channel only gets 8 bits. That means 256 values. Now you may be wondering why the alpha is reading 255 and not 256, that's because that last value there to get us to 256 is zero so it starts at zero and it ends at 255. So anything that reads at 255 is fully opaque, it does not matter what the color is the color is in this example irrelevant, it makes no difference. You can change the color to anything you want as long as this rectangle has 100% opacity it will be doing the same thing. It doesn't matter what the color is. Now in this larger rectangle here I have a gradient. And if I open that up and select it, I'll open up the fill here so you can see how that's working. A gradient goes from red to black. But again the color doesn't matter because this layer is set to alpha matte, which means it's only looking at the transparency. It doesn't matter what the color is. So in this gradient the opacity for the gradient has been set on one side to 0 and on the other side to 100%. So watch what happens if I take this rectangle and I adjust its gradient. If I change the color. Nothing will happen. It doesn't matter what color it is. However, if I change its opacity, then you can see a change, all right? So when your fill layer is set to Alpha Matte or alpha inverted, it's getting all of it's transparency information from this layer's transparency, not it's color information. And there is two ways to set this, you can set it to regular alpha matte, or you can set it to alpha inverted matte, which is the exact opposite. It's as if I rebuilt this layer but I flipped all the opacity values. This is just a much easier way to do that. Sometimes, you need to set your layer to Alpha Matte, sometimes you need to set it to Alpha Inverted Matte. Let's look at another example. In this Luma Matte's composition, I basically have the same thing, the same three layers. However the pattern layer has been set to luma matte so it's going to be getting its transparency information from the luminescense of this matte layer directly above it. And if solo that for you you can see that this time I've set this up to be black and white and that's because things that are fully white and you can see if you look at the info panel that this rectangle is reading 255, 255, 255, that means it's fully white. And When you're set to luma matte, things that are fully white are fully opaque. See that? Things that are black, are fully transparent, so you can see that my gradient goes from black to white here, and that is what is being reflected with my pattern layer here. Let me show you an example of how you might actually use alpha and luma mattes in some real projects. I'm gonna jump over to my Louvre composition here. I'll just play a little bit of this so you can see what's going on. Now, in order to create this look, I'm using an alpha matte. There's other ways to do it, for sure, but the easiest way for me was to use an alpha matte. So what I have going on here is a background layer which is a video clip with some effects applied to it. I have a curves effect which is darkening it. I have a third party effect from Red Giants Universe called RGB separation, which is giving it this cool RGB split effect here. And then I'm using a Gaussian blur to blur it out. On the layer that's directly above it, you can see that there is a track now applied which you can also see just to the left of the layer name here. Those little icons indicate that this has a track matte applied, and this is the matte layer right here. So this is the same footage layer. If I set this to None you can see that the blending mode has been set to Add. So if I set that to Normal, you can see it's just the same, exact footage layer as the one below. I'll set it back to Add. When I set this to alpha matte it's going to be using the layer directly above it for its transparency and in this case that is a text layer. So that is what is doing this word cut out sort of effect here. It's just a simple text layer and an alpha matte. Let me show one other example here, Now this is something that i actually used on a project this last year, So let me walk you through how this works. Right here I have a pre-comp called waves. If I double click on that we can jump inside that pre-comp and it's here I have a footage layer with a couple of effects applied to it. It's set to a blending mode of multiply and below there I have this kind of paper texture layer here. And the idea is I just want some of that paper texture to show through on my footage layer here, alright? So that's the thing that I want to reveal. That's what I wanna use the map for. This is the map that driving that reveal. This is what's driving those transparent pixels on the waves layer. If we jump in here, you can see that this is just a comp made of a bunch of ink drop elements that I found at envato elements, and I've arranged them just how I want them to get this effect where it looks like the ink is, kind of bleeding from the center and expanding outwards. You can see that there's some animation happening here, just some basic position and scale animation, because most of these are single ink drops. And I wanted it more to look like a line of ink expanding across the screen. Now, all of these layers, if I double click on one, it will bring it up in the layer viewer here. All these layers are black and white. But I'm combining all of these to use as one matte. And I'm doing that by setting all of these layers here to multiply, and then I have a white solid on the background. So it's essentially compositing them all on top of each other, and the effect is that I get one pre-comp that's just black and white, so over here I'm using that ink matte As a track matte. In this particular case, and I'll solo that so you can see just the waves layer, it's set to Luma Inverted Matte. And that's because all of those ink drops are essentially backwards for what I need. If I set this to Luma Matte, It does the opposite of what I want. Now, there's like 100 different ways that you can fix that. The easiest way is to just set this to Luma Inverted Map. And then it does exactly what I want it to do. Now you saw me mentioned a few effects in this lesson and you're going to learn more about effects coming up in the next lesson so check that out coming up next.

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