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Follow the LeaderTime offset with After Effects expressions
One of the more frightening aspects of expressions is the math that can sometimes be involved. Another is that you have to learn a programming language. ?Im an artist for jeebus sake! I was an art/graphic design/video major in college to avoid math! While that may have been true five or six years ago, animation, compositing, and video packages have become more powerful and have the ability to calculate and simulate real world physics as long as you understand the math.
The Pickwhip Expression
The simplest expressions can be created easily with the Pickwhip tool in the Timeline. For example, if you wanted to have a layer take on the Position property of another layer, Pickwhipping to that property would return an expression similar to the following:
What does this expression mean? By breaking down the components of the formula, you will begin to understand the language behind expressions.
First, all expressions must start with a Global Object. The default Global Object is the property that you are applying. Position is a good example of this. By default when you turn on expressions for the Position property of a layer, the first thing entered in the Expression Window is Position.
If we wanted to add a Wiggle value expression to the Position Property, we could type the expression
However, because the Wiggle Value (or as will be known for the rest of our discussion as simply Value), is being applied to the Position Property, there is no need to tell After Effects, ?Hey, Position Property! Animate your Position and Wiggle. Instead, we can drop the Position Global Object and simply use the value to say, ?Hey, Position Property! Wiggle!
So the expression to wiggle the Position Property of a layer would be
Remember: You do not need to specify the property for an expression for the property on which the expression is written.
Note: The period between the Global Object and the Value creates a chain of object references. This is important because it allows us to tie multiple values together to make a more complex expression.
Some of the other Global Objects that you can apply to a layer include:
Related Keywords:expressions, array, espn, after effects, schleicher, adobe, animation, compositing
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