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Expressions are one of the most powerful but underused features in After Effects. They can be used to animate layer properties with code, as compared to explicitly keyframing every value in the Timeline, and have multiple parameters and layers that follow the lead of a master layer or controller effect, making it much easier to coordinate complex animations and quickly accommodate client changes. In this introduction, Chris Meyer shows how to let After Effects do most of the work by creating simple but very useful expressions that can be put to work on a wide variety of jobs.
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 Online Training Library®.
Let's go back to the Project panel and look at another idea of what you can do with Wiggle. I'll double-click the movie Idea2- Lens Flare and RAM Preview this one. You'll see that we have a flare that we have centered on the top of this building, but rather than maintaining a constant brightness, it's doing two things: one, it's blinking, and two, it's fading out in intensity as time goes on. Let's explore how we made that happen. I'm going to double-click the comp Idea2-Lens Flare.
Select the lens flare solid. Remember we like to apply light effects like lens layer to black solids, then use blend modes to go ahead and combine them on top of the underlying footage. And I'll type EE to review all expressions. Widen this out little bit. We see two things are going on. Flare Brightness is indeed keyframed with the value at the beginning and end, and it also has an expression attached. Let's turn off the expression for moment so we can see what the keyframes are doing. The keyframes are just creating a very simple fade of the Flare Brightness, with the values keyframed to match more or less the brightness of the scene.
So as we go further in the night, the flare itself becomes less intense as well. Then we added our Wiggle expression. The first value is how fast. I went for 10 wiggles a second to get a very erratic point light. Then for the second parameter of how much to wiggle by, I use the word value. You may remember from earlier in this lesson that value says, take whatever the underlying value is for this layer and use that inside of just a number that I type in. Therefore, as the Flare Brightness is keyframed to drop from 75% down to 25%, that is the amount of wiggle being used at the same time.
And the reason I did that is I didn't want a constant value for my wiggle. When the flare is very bright, my wiggle should be going through a much wider range of values. When the flare brightness was lower, the Wiggle value should be a smaller range of values. That's why I use the word value to take advantage of these values I already keyframed. I'll turn the expression back on. You will see that the Wiggle values are pretty low down here at the end and pretty extreme here at the start. I'll go ahead and press 0 again to RAM Preview.
And there's the final result of our blinking lens flare using Wiggle in conjunction with keyframes.
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