Join Angie Taylor for an in-depth discussion in this video Expression language, part of After Effects Expressions for Premiere Pro Editors.
- We've already established that expressions understand values so if I had an expression to the rotation property go to Animation, Add Expression I could just replace the default expression with a number. So if I type in 100 that's what that value will be. Expressions also understand math so if I type in 100 + 50 it will understand that value of 150. But expressions can also understand words, for example if I animate the hours hand, say from zero to 12 so that's giving it 12 revolutions, then I can link this expression to that value using what's called the pick-quip and when I do that it writes an expression for me it's referring to thisComp_Layer("Hours Outlines") transform.rotation So some of the words that you get in expressions are really easy to understand.
Parts of the expression language is about After Effects, it refers to things like the Comp, the Layer the transform property group rotation value. This is almost like an address for this value to get its property from which is over here. And now you'll see that both of those animate at exactly the same time and of course I can use a combination of words and math so if I divide that result by two, then that one goes at half the speed of the other one.
Okay so you're combining words with math. Now there are other words that you can use in expressions And if we have a look in this menu here, this is the Expression Language menu, you can see some of those words in here. Now this can be a bit overwhelming this menu. But if you have a look in something like the Property menu, you can see it refers to things like value and velocity which we recognize as well from the Graph Editor in After Effects or speed so some of the words will be familiar you'll see that wiggle's in there and the wiggle expression is very similar to using the wiggler panel and we can have a look at that a little bit later.
There's other math in here we've got degreesToradians and Color Conversion again we'll have a look at these later. And then we have the Interpolation language, where we have things like the linear expression which will allow you to convert ranges. There's also things like the Global section which refers to things like comps, footage, thisComp, time we refer to as well, colorDepth and if we go into the Comp menu we can refer to things like things inside the Comp like the layers or the width height duration of the Comp .
So you can refer to all of these language elements within your expressions. So let's have a look at how something like that would be put together something that refers to the Comp and also the Comp width or height. So if we have a look at this Composition 03 Shapes and double click that you'll see there's an expression in here that uses those elements in what we call an array to determine the x value and the y value we say (thisComp.width/2, thisComp.height/2 And that's giving it a position that's half the Comp width and half the Comp height.
Now the great thing about this is if I go up here and change my Composition settings to a different sized Comp it still maintains that position in the center of the Comp. Now it would do that anyway if my Layer was in the middle of a Comp but imagine if I say [thisComp.width/3 and we'll do that here as well so divided by three moves it up to this corner and now you'll see I can go to different Comp sizes and it's going to maintain a position which is a third of the Comp height and a third of the Comp width in terms of x and y value.
So that's a little bit about the different types of words that you'll find in Expressions. Don't worry too much about understanding the whole Expression language menu to begin with. All you need to understand is that words can be used in combination with values numbers and other symbols to create Expressions. And we'll have a look at some of those symbols in the next tutorial.
After Effects Expressions for Premiere Pro Editors is a creative, project-based workshop. Editors take a basic Premiere Pro edit and bring it to life using After Effects expressions and Dynamic Link, following author Angie Taylor's expert instructions. The concepts are broken down into manageable 3–5 minute videos, covering techniques such as randomizing effects, linking animation and color to sound, automating animation, and more.
- Linking footage from Premiere Pro in After Effects with Dynamic Link
- Understanding the expression language
- Automating animation with expressions
- Randomizing effect properties
- Linking color and light changes to audio
- Creating camera shake with a wiggle expressions
- Linking keyframes to create a lightening strike effect
- Synchronizing color and other design elements
- Creating amazing text animations