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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®.
We are going to end this introductory lesson on expressions with a few more ideas of what you can do with the Wiggle expression. I'll be in the Idea Corner folder, and first let's open up the movie Idea1-Nervous Text.mov. I will play through this, and you see we have some text that is randomly going in and out of the focus. Rather than requiring a lot of keyframing, this is a trick that just required a relatively simple Wiggle expression. I will open up the comp Idea1-Nervous Text, select the text layer Interference, type EE to reveal all the expressions, and type Shift+E to also show all effects applied to this layer.
To create this blurred look, I used the Directional Blur effect. I'll press F3 to open up the Effects Control panel. And it contains just two parameters: Directional Blur and the Blur Length. Down here in this Timeline panel, I applied the Wiggle expression to both of those parameters. But instead of just typing in numbers, I also created a series of Expression controls to give me a user interface on the amount of this blur. I created one of the Wiggle Speed in terms of wiggles per second. I created the Wiggle Amount--how long the blur is--and Wiggle Angle, for what the direction of the blur is.
And then I just used the pick whip to go ahead and connect the wiggle parameters to these sliders. I used the Wiggle Speed slider for both the Directional Blur's direction and Blur length. And for the amount of Wiggle, I used the Angle Control for the Direction, that's why the Blur seems to head off in different directions, and also rotates in the middle of wiggles, and then I use the Wiggle Amount slider for the Blur Length. Now there is one other little anomaly you might have noticed.
There's long periods of time there does not seem to be any blur at all. It's not constantly blurred. The reason that is is because the Wiggle expression creates both positive and negative numbers. However, Blur Length can only be a positive number. You cannot have a negative amount of blur. Therefore, any time that Wiggle would have kicked out in negative number, the Blur Length essentially goes down to 0. The Blur effect is clipping the values, it does not go below 0.
So anytime that you see no Blur Length at all, what's really going on is the Wiggle expression is kicking out a negative number at that particular point in time. You'll run into several parameters, such as Opacity, Blur Lengths et cetera that don't go negative, so when you apply Wiggle to them, you'll either get this result where they appear to be off half the time, or you will need to dive deeper into expressions to program around that.
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