Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 554

The element
5
thisComp
To determine what can follow
objects" on page 556.
Note that returns a Comp. Next, look at "Comp attributes and methods" on page 562 to see which
thisComp
attributes and methods you can use with a Comp. One option is
parentheses specifies the layer that you want to use. For this example, we assume that Solid 1 is the first layer in your
composition. To retrieve values from the first layer in the active composition, type
expression, to get the following:
thisComp.layer(1)
Again, look at the expression elements reference to see that
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General attributes and methods" on page 565, and find the element you want to use. For example, if you want to
access the Position property's values for the layer, type
thisComp.layer(1).position
From "Layer General attributes and methods" on page 565, you can see that the
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property. Look up "Property attributes and methods" on page 572 and notice that you can add a time factor to the
expression. To add a specific time, such as current time plus 2 seconds, type
the expression to get the following:
thisComp.layer(1).position.valueAtTime(time+2)
From "Property attributes and methods" on page 572, notice that the
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Array. When an expression returns a Number, Array, or Boolean (true or false), you cannot add further attributes or
methods to the expression (if you want, however, you can add arithmetic operators, such as
See also
"Using the expression elements reference" on page 555
Show expressions and the expression graph
In Graph Editor mode, the single expression field appears as a resizable text box at the bottom of the Graph Editor
and shows only the expression for the selected property. To show multiple expression fields simultaneously, the
Timeline panel must be in layer bar mode.
To toggle between layer bar mode and Graph Editor mode, press Shift+F3.
• To show only properties with expressions, select one or more layers, and then press EE.
• To show the expression field in the Graph Editor, choose Show Expression Editor from the Choose Graph Type
And Options menu at the bottom of the Graph Editor. When you add a new expression to a property, the
expression editor is shown, regardless of this setting.
To resize the expression field, drag its bottom edge up or down.
• To see how an expression changes the value or velocity graph, click the Show Post-Expression Graph button
while showing the value or velocity graph in the Graph Editor.
The dimly colored graph displays the value or velocity before the expression is applied, and the brightly colored graph
displays the value or velocity after the expression is applied. Turning on the graph overlay for the Position property
also changes the motion path display in the Composition panel so that you can see the expression-affected path.
is a global attribute whose value is a Comp object representing the current composition.
in your expression, look up the return value for
thisComp
. The index, or number, inside the
layer(index)
returns a Layer. Look at "Layer
layer(index)
at the end of the expression to get the following:
.position
.valueAtTime(time+2)
valueAtTime
AFTER EFFECTS CS3
under "Global
thisComp
at the end of the
.layer(1)
attribute returns a
position
at the end of
method returns a number or
, , , and ).
+ - * /
548
User Guide