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The After Effects Apprentice videos on lynda.com were created by Trish and Chris Meyer and are designed to be used on their own and as a companion to their book After Effects Apprentice. We are honored to host these tutorials in the lynda.com library.
- Creating, erasing, and animating brush and clone strokes
- Using Paint to reveal a layer over time
- Creating animated distortions to flat artwork with the Puppet tools
- Replacing backgrounds with the Roto Brush
Skill Level Intermediate
If you have the Exercise Files, go ahead and open composition 02-Write On*starter. If you don't have the Exercise Files, just find any image such as our auto bird here that has an interesting shape that you might like to write on. This technique will work with almost any image. My layer is currently on a transparent background. In order to wipe on a layer, it also has to be invisible. However, it's kind of hard to paint on a layer if you can't see it.
So we'll make the layer invisible in a later step. So let's set up the Paint and Brush panels so that we can write on this layer. The first thing we need to do is to double- click the layer to open it in the Layer panel. So take a moment to set up your workspace, remember, you have to paint in the Layer panel. We'll make sure we're at 100% and full resolution and we'll select the Brush tool. The Paint and Brushes panel should also be visible and they will be set to whatever settings you used in the last movie.
We'll make sure Opacity is set to 100% and Flow is set to 100%. The color we need to use is white. So I will just select the black and white and then switch it so that white is the foreground color. I'll also make sure that the mode is set to Normal and that the Channels pop-up is set to Alpha. Now, this is very important. We only want to paint the white stroke in the layers Alpha. However if you do make a mistake, you can always set the Channels pop-up after the fact in the Timeline.
When you set Duration to Write On mode, it automatically creates keyframes for the end parameter. Of course if you forget to set it to Write On, you can just create the end keyframes later on. Now, even though we set the Paint panel to only paint on Alpha, we'll probably also want to set Show Channels to Alpha channel. Remember you can toggle back and forth quickly by Option or Alt+Clicking on the Show Channels button. You'll notice that the Alpha channel has a little texture in it.
That was picked up when I scanned the image because I wrote on a textured paper. If you're using your own image, it's likely the Alpha Channel will be completely white. The next thing we want to do is set a Brush size. So I will press the Command key and size my brush to somewhere around 50 pixels. Feel free to set the Hardness value to taste. You can always change it later. I will set it to a medium hardness. I don't want it to be too soft as I wipe on the stroke. Now when I am using Duration Write On, the first keyframe for end will be placed at the current time.
Also notice that the comp is 10 seconds long. When you're using Write On, it automatically places the second keyframe when you release the mouse. So if you paint very slowly and take longer than 10 second, your second keyframe will be after the end of the comp and you'll have to retrieve it. On the other hand, you don't have to rush and try to paint on your layer in real time. It's very easy to move the second keyframe to retime the stroke. Just try to keep it under 10 seconds. Another thing you don't want to do is start painting left and right like this.
If that's all you're going to do, you may as well just use a transition called Linear Wipe. What we're trying to do is get some interesting movement and you can start at the top or at the bottom, but do try and paint in one continuous stroke. Another thing I want to mention about timing. Let's say you start off painting very slowly and then you go very quickly and then you go very slowly. All of that timing will be embedded in your paint stroke. So even though when you're finished, you'll end up with two keyframes that are linear.
It doesn't mean that the personality of your stroke will be linear in nature. After Effects will remember all the subtle timing in your stroke. Of course you can always ease into or ease out of those two keyframes, but a large amount of the personality is embedded in the stroke as you paint. Now they're all set up, as soon as we click with the mouse, it will start recording the stroke. Unfortunately, I just noticed that I am painting with a black stroke. I always forget that when you change the Channels to Alpha, it switches the colors to black and white.
So I need to switch it back so that the foreground color is white and we'll undo and let's start again. This time I will paint with the tablet using Pen Pressure. I will start up slowly then pick up speed. You might have to try your stroke a few times until you get a move that you like. Let's say I am happy with that. When I stop painting, the stroke will seem to disappear. Not to worry, it's only because at the current time, the animated stroke hasn't started yet.
With the layers selected, I will press U to see my keyframes. At this point I should see two keyframes for end, but it looks like I took more than 10 seconds as the second keyframe is after the end of the comp. But that's easy to fix. Instead of making the composition longer you can simply drag this layer back and there is my keyframe and I probably want the stroke to be only a few seconds long. Then I'll move the bar back, to make sure the first keyframe starts at time zero. I'll move the second keyframe to 4 seconds and let's RAM preview.
Remember that the preview plays in the Comp panel. So we'll want to resize the panel. Notice that if you varied the speed when you were drawing, it's reflected in the animation. I will press N to set the work area at little after the second keyframe. If you find the animation is too slow or too fast, just move the second keyframe to retime it. Before we move on, it's very important to return to using the Selection tool, so you don't accidentally replace your animated stroke.
Notice that Brush 1 is selected in the Timeline. If I so much as click in the Layer panel to bring it forward, I'll actually replace Brush 1, when I move the Time Marker, I don't see my animated stroke anymore, because I've replaced it. If that happens to you, you can undo, but it's best to return to the Selection tool as soon as you're finished painting your stroke. In the next movie, I will show you how to make the layer invisible and clean up the edges.