| Expressions are tools. Just as you use the Rotation tool and the Pen tool, you can use Expressions to control animation and composition in After Effects (AE).
Whereas you use most tools by clicking on their icons (e.g., the pointer or the pen) and clicking or dragging with the mouse, you use Expressions by typing commands on the keyboard. That’s what Expressions are: typed commands. You type these commands to tell AE what to do, and—assuming AE understands your commands—it does what you want it to do.
But you don’t always have to type to add an Expression. There are some clever click-and-drag tools that will save you time. But these tools just do the typing for you. Expressions are still typed commands.
Expressions are also like recipes—directions for baking some yummy dessert: First, mix eggs and fl our; then add sugar; then bake at 375 degrees for 20 minutes. Imagine you wrote such a recipe, and a helpful robot (wearing a chef’s hat and apron) read it, followed the directions, and baked you a cake. With Expressions, you type out the instructions, and the robot—After Effects—bakes you a cool effect.
Most Expressions command AE to bake numbers. For instance, the Expression 1 + 2 commands AE to bake the number 3. It’s as if you’ve typed, “take a yummy one and a scrumptious two, and pop them in the addition oven. ” The AE robot does so, and a few nanoseconds later, it hands you a steaming, delicious 3 on a plate. (Don’t worry; most of the Expressions you’ll use, at least when you’re starting out, won’t look like math problems.) |
