ADOBE AFTER EFFECTS 7.0
User Guide
588
5
Drag the pick whip to the hour hand’s Rotation property. The following expression appears:
t h i s C omp. l aye r ( " h ou r h and " ) . rot at i on
6
To make the minute hand rotate 12 times as fast as the hour hand, add
* 1 2
at the end of the expression as follows:
t h i s C omp. l aye r ( " h ou r h and " ) . rot at i on * 1 2
Example: To increase blur with depth
The following example shows how to use the pick whip to control blur by a layer’s position in z-space. This expression
is useful for making an object blurrier as it travels farther away in space.
1
Import or create a layer in the shape of a star. (See “About layers” on page 149.)
2
Click the 3D switch for the layer and set Position keyframes so that it moves farther away in z-space. (See “To
designate a layer as 3D” on page 175 and “Using keyframes” on page 192.)
3
Apply the Fast Blur effect. (See “Applying and controlling effects” on page 348.)
4
Select the Fast Blur effect’s Blurriness property in the Timeline panel and choose Animation > Add Expression.
5
Drag the pick whip to the Position property. The following expression appears:
p o s it i on [ 2 ]
6
If the blur is too intense, cut the blur amount by one-fifth by adding
/ 5
to the end of the expression as follows:
p o s it i on [ 2 ] / 5
Manually entered expression examples
Example: To position one layer between two others
This example expression positions and maintains one layer at a balanced distance between two other layers. To
achieve this effect, you need three layers in your composition.
1
Start with three layers. (See “About layers” on page 149.)
2
Create motion paths for the first two layers in the Timeline panel. (See “To create a motion path” on page 210.)
3
Select the Position property for the third layer and choose Animation > Add Expression.
4
Select the default expression text and type the following:
( t h i s C omp. l aye r ( 1 ) . p o s it i on + t h i s C omp. l aye r ( 2 ) . p o s it i on ) * . 5
Example: To create a trail of images
This example expression instructs a layer to be at the same position as the next higher layer in the Timeline panel,
but delayed by a specified amount of time (in this case, 0.5 seconds). You can set similar expressions for the other
geometric properties. This expression requires two or more layers.
1
Start with two solids that are scaled to approximately 30%. (See “To create a solid-color layer” on page 150.)
2
Create a motion path for the first layer. (See “To create a motion path” on page 210.)
3
Select the Position property for the second layer and choose Animation > Add Expression.
4
Select the default expression text and type:
t h i s C omp. l aye r ( t h i s L aye r, - 1 ) . p o s it i on . v a lu e At Ti m e ( t i me - . 5 )
Summary of Contents for AFTER EFFECTS 7.0
Page 1: ...Chapter 1 User Guide...
