Using Help | Contents | Index Back - Adobe AFTER EFFECTS 5.5 Help Manual

Adobe After Effects Help
Using Help | Contents
6 Click outside the expression to activate it. All layers follow the same path, and each is
delayed .5 seconds from the previous.
Creating a bulge between two layers
Use an expression to synchronize the Bulge Center parameter of the Bulge effect in one
layer with the position of another layer. For example, move a magnifying glass over a layer
and make the contents under the magnifying glass bulge as the glass (or the underlying
layer) moves. This expression uses the "from_world" element, which makes the expression
work correctly regardless of whether you move the magnifying glass layer or the under-
lying layer. You can rotate or scale the underlying layer and the expression stays intact.
You can also use other effects, such as Ripple, with this expression.
To create a bulge between two layers:
1 Start with two layers. Make one layer a magnifying glass or similar object with a hole in
the middle and name it Magnifier.
2 Create a motion path for the magnifying glass layer.
3 Apply the Bulge effect to the other, underlying layer.
4 Select the Bulge effect's Bulge Center property in the Timeline window and choose
Animation > Add Expression.
5 Select the default expression text and type the following:
from_world(this_comp.layer("Magnifier").position)
6 Click outside the expression to activate it.
Moving a layer in a perfect circle
You can create an expression without using properties from other layers. For example, you
can make a layer revolve in a perfect circle or move back and forth diagonally.
To create a circular movement in one layer:
1 Start one layer.
2 Select the Position property for the layer and choose Animation > Add Expression.
3 Select the default expression text and type:
add([this_comp.width/2, this_comp.height/2],
[Math.sin(time)*50, -Math.cos(time)*50])
4 Click outside the expression to activate it.
After Effects expression language guide
Use the elements in the following sections, along with standard JavaScript elements to
write your expressions. Remember that you can also use the Expression Language menu
at any time to insert functions into an expression.
See "Accessing elements in an expression" on page 250 for procedures on using this
guide.
Expression language guide key
Use the following key when referencing the expression language guide:
Using Help | Contents
| Index
| Index
Creating Expressions
Back 254
Back 254