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The pop_property () function obtains the current selection from the specified Property
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menu.
The pop_channel () obtains the current selection from the specified Channel menu.
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For each function, you must specify which of the two sets of menus to use. Type a 1 in the
parentheses to specify a menu in the first set; type a 2 in the parentheses to specify a
menu in the second set. Your script need not use all six menus; any selections in the
unused menus are ignored. In general, substitution functions are used inside other
functions that require layers, properties, or channels as variables, such as the value () or
velocity () functions. For example, the following line uses the pop_layer () function inside
the value () function:
delta = value(pop_layer(1),position) - value(pop_layer(2),position);
The line above obtains the position value for the layer selected in the first Layer menu and
subtracts the position value for the layer selected in the second Layer menu. You can also
use a substitution function on the left side of an assignment when creating a keyframe. In
the following example, a rotation keyframe is created for the layer selected in the first
Layer menu:
value(pop_layer(1), rotation) = ang;
Use the substitution functions to select properties and channels in up to two layers. Both
sets of menus list layers, properties, or channels, as follows:
The Layer menus list all available layers in the composition.
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The Property menus list the properties available for the layer selected in the corre-
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sponding Layer menu.
The Channel menus list the channels available for the property selected in the corre-
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sponding Property menu.
If you need to select a third layer, you can create a variable in the script where you type the
name of the layer. For an example, see the Span script.
Using the language element menus (PB only)
In the Motion Math window, you can save time writing scripts by using the language
element menus, which insert selected language elements in the script editor. Without
having to type or remember formats, you can insert any layer property functions, math
functions, operators, and constants into a script, and then edit them as needed.
To insert language elements in a script:
1 In the script editor, click the insertion point at the appropriate location.
2 In the Motion Math window, select language elements from one of the four language
element menus: Functions, Math Functions, Operators, and Constants.
3 Edit the inserted elements, as needed, to create your script.
Motion Math language reference (PB only)
The Motion Math language includes the functions, math functions, operators, and
constants shown in the following sections.
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Using Motion Math (PB only)
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