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Headings represent expression objects. All elements listed below a heading are
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attributes (that you can retrieve from the object) or methods (that you can call on the
object). Many of the attributes and methods return other objects—look up those
object types in this guide to determine how to continue your expression.
Italic text at the beginning of a description represents the return value type. Some
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return values include a number in square brackets—this number specifies the
dimension of the returned property or array. If a specific dimension is not included, the
dimension of the returned array depends on the dimension of the input.
Bold text represents the expression language element to type in your expression.
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(Bold Italic) text inside parentheses represents the argument(s), which is the type of
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information that you need to add inside the parentheses. If an argument contains an
equal sign (=) and a value (such as t=time or width =.2), the argument uses the included
default value if you don't specify a different value.
{Italic and Roman} text inside curly brackets represents the argument description. Some
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argument descriptions include a number in square brackets—this number indicates
the dimension of the expected property or array. If a specific dimension is not included,
any dimension will work.
Roman text is a description and possibly an example of the element.
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Global attributes and methods
Only a global attribute or method, or a constant value, can appear in an expression with
nothing to the left of it.
Global objects
Layer, Light, or Camera this_layer Represents the Layer itself. Because "this_layer" is the
default object, its use is optional. For example, you can start an expression with
"this_layer.width" or "width" and get the same result.
Comp this_comp Represents the composition containing the expression. For example,
you can start an expression with "this_comp.layer(2)" .
Number time Represents the composition time, in seconds, at which the expression is
being evaluated. See "Expression time" on page 251.
Number value Represents the value at the current time for the property containing the
expression. For example, you can include "value + 5" in an expression.
Comp comp(name) Retrieves another composition by name.
Footage footage(name) Retrieves a footage item by name.
Vector math methods
These are global methods that perform operations on arrays, treating them as mathe-
matical vectors. Unlike built-in JavaScript methods, such as Math.sin(), you do not use the
Math prefix with these methods. Unless otherwise specified, vector math methods are
lenient about dimensions and return a value that is the dimension of the largest array,
filling in missing elements with zeros. For example, the expression "add([10, 20], [1, 2, 3])"
returns [11, 22, 3].
Array add(v1, v2) {v1 and v2 are arrays} Adds two vectors, componentwise.
Array sub(v1, v2) {v1 and v2 are arrays} Subtracts two vectors, componentwise.
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Creating Expressions
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