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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 open up our third comp, Idea3- Electric Arcs, and take a look at that one. Again, I'll press 0 on the numeric keypad to RAM Preview, and this will take a little while to calculate because we do have a few things going on. You see these different lightning bolts seeming to search around the screen. Question is, how do we do this? Well, again, we used our friend the Wiggle expression, in junction with another effect. You'll notice in my timeline I've got three lightning solids, all in Add mode. Just like lens flares, the advanced lightning effect is something that generates light.
Now, I prefer to put them on their own black layers so I've got more control over how I blend their opacity and what blending mode I use. I've also created a MASTER CONTROLLER, again, for Wiggle Amount and Wiggle Speed. For the Advanced Lightning effect, I'll type EE for expressions. I created what looks like a very long complex Wiggle expression, but actually it's very simple. Again, it's just Wiggle, how fast, and how much? And again, I just use the Pick Whip tool to select these sliders to stand in for those two values. And if you actually read the expression, it's not that scary.
And this comp is a layer named MASTER CONTROLLER with an effect called Wiggle Speed used its slider, and very similar for the Wiggle Amount. By using a MASTER CONTROLLER, I have something I can keyframe and more easily adjust to decide how far I want these lightning bolts to reach out and how fast I want them to search around. Once I created one solid like this, I just duplicated it two more times. Again, remember that the Wiggle expression randomizes for every layer that it's applied to.
I could create even more of these, just duplicate a few more times and create as many lightning bolts as I want, each one randomized from the others. I will RAM Preview this, and now we've got lots of electricity flowing around our comp. I'll just go ahead and play that back, because it does take a little while to render. And in this case where I knew that I wanted to create more than one lightning bolt, it made a lot of sense to create one MASTER CONTROLLER, so I only had one set of parameters to adjust for all of those lightning bolts. I can pull them all down together, take this down to 0, or expand them all out, which gives me lots of possibilities for keyframing, et cetera.
So this comes back around to where we started. If you can keyframe it, you can probably apply an expression to it, including even wiggle it to randomize its value. Now, by no means has this been an exhaustive course on expressions. It's a very deep subject, where you can go ahead and program your own ideas of how things are supposed to animate. And it is a subject we covered in more detail in our bigger book, Creating Motion Graphics. However, we really think that for a lot of After Effects artists what we have shown you in this lesson is all a lot of people need to know to get a lot out of expressions: how to borrow values from other layers, how to translate between values of different layers, and how to use Wiggle to randomize your animations with a minimum amount of work.
We hope you found this useful and that it got you over your fear of expressions, so that you can go ahead and add them to your toolkit as well.
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