|
Introduction to Expressions
Geometry
Project Index
HOME
|
Layer Parameters
These are the layer parameters to which you can apply expressions. (You can also apply expressions to effect parameters and to some mask parameters.)
Use this table to know what each parameter expects from your expressions: how many dimensions, what kind of units, and common value ranges. For instance, using this table, you can see that an expression applied to the position parameter should produce results of 2 dimensions (3 if a 3D layer), with each component typically ranging from zero to the comp height or width.
| anchor_point |
2* [x, y, (z)] |
pixels |
±inf |
0–layer width, height |
| position |
2* [x, y, (z)] |
pixels |
±inf |
0–comp width, height |
| scale |
2* [width, height, (depth)] |
percentage |
±inf |
±100 |
| rotation |
1 |
degrees |
±inf |
0–360 (periodic) |
| opacity |
1 |
percentage |
0–100 |
0–100 |
| orientation (3D-only) |
3 [x, y, z] |
degrees |
±inf |
0-360 (periodic) |
| audio_levels |
2 [left, right] |
decibels |
-192–24 |
-48–12 |
| ambient |
1 |
percentage |
0–100 |
0–100 |
| diffuse |
1 |
percentage |
0–100 |
0–100 |
| specular |
1 |
percentage |
0–100 |
0–100 |
| shininess |
1 |
percentage |
0-100 |
0-100 |
| * 3 dimensions when layer is 3D. |
Global Objects
This table lists all of the global objects available in After Effects, and the type of objects they return. Anytime you refer to an element outside the current layer, you'll need to start with one of these objects.
| this_layer |
Layer or Light or Camera |
| this_comp |
Comp |
| comp("name") |
Comp |
| footage("name") |
Footage |
| time |
Number |
| value |
Number |
Comp Attributes and Methods
This table lists all of the attributes, methods and sub-objects belonging to comp objects. In addition, it tells you what kinds of objects, or type of values, are returned by each method or attribute.
| active_camera |
Camera |
|
|
| width |
Number |
1 |
pixels |
| height |
Number |
1 |
pixels |
| duration |
Number |
1 |
seconds |
| frame_duration |
Number |
1 |
seconds |
| bg_color |
Vector |
4 |
0 to 1 |
| shutter_angle |
Number |
1 |
degrees |
| shutter_phase |
Number |
1 |
degrees |
| num_layers |
Number |
1 |
|
| pixel_aspect |
Number |
1 |
NA (width/height) |
| layer(index or name) |
Layer |
|
|
| layer(other layer, relative index) |
Layer |
|
|
Layer Attributes and Methods
This table lists all of the attributes, methods and sub-objects belonging to layer objects. In addition, it tells you what kinds of objects, or type of values, are returned by each method or attribute.
| width |
Number |
1 |
pixels |
| height |
Number |
1 |
pixels |
| start_time |
Number |
1 |
seconds |
| in_point |
Number |
1 |
seconds |
| out_point |
Number |
1 |
seconds |
| has_video |
Boolean |
1 |
Boolean |
| has_audio |
Boolean |
1 |
Boolean |
| active |
Boolean |
1 |
Boolean |
| audio_active |
Boolean |
1 |
Boolean |
| audio_levels |
Property |
2 [left, right] |
decibels |
| index |
Number |
1 |
Number |
| parent |
Layer, Light or Camera |
|
|
| anchor_point |
Property |
2 or 3 [x, y, (z)] |
pixels (layer space) |
| position |
Property |
2 or 3 [x, y, (z)] |
pixels |
| scale |
Property |
2 or 3 [width, height, (depth)] |
percentage |
| opacity |
Property |
1 |
percentage |
| rotation |
Property |
1 |
degrees |
| orientation (3D-only) |
Property |
3 [x, y, z] |
degrees |
| ambient (3D-only) |
Property |
1 |
percentage |
| shininess (3D-only) |
Property |
1 |
percentage |
| casts_shadows (3D-only) |
Boolean |
1 |
Boolean |
| accepts_shadows (3D-only) |
Boolean |
1 |
Boolean |
| accepts_lights (3D-only) |
Boolean |
1 |
Boolean |
| time_remap |
Property |
1 |
seconds |
| source |
Comp or Footage |
|
|
| mask(index or name) |
Mask |
|
|
| effect(index or name) |
Effect |
|
|
Footage Attributes and Methods
This table lists all of the attributes, methods and sub-objects belonging to layer objects. In addition, it tells you what kinds of objects, or type of values, are returned by each method or attribute.
| width |
Number |
1 |
pixels |
| height |
Number |
1 |
pixels |
| duration |
Number |
1 |
seconds |
| frame_duration |
Number |
1 |
seconds |
| pixel_aspect |
Number |
1 |
NA (width/height) |
Property Attributes and Methods
These are the attributes and methods belonging to Property objects such as 'rotation' and 'opacity'. How do you know when you have a Property object? By checking the 'returns object of type' column in the Layer Attributes and Methods table, above. For instance, 'position' returns a Property object. This table is how you know when it's OK to write something like 'position.value_at_time(0)'.
| value |
Number or Vector |
|
| value_at_time(t) |
Number or Vector |
|
| velocity |
Number or Vector |
|
| velocity_at_time(t) |
Number or Vector |
|
| speed |
Number |
1 |
| speed_at_time(t) |
Number |
1 |
Vector Math Methods
These are the vector math methods which After Effects has conveniently made available as part of the default object, so that you don't need to write "Math.add(vector1,vector2)". If none of these methods fits your need, you may want to consult a Javascript reference to see if there's an additional, more useful, tool belonging to the Math object.
| add(vector1, vector2) |
highest of vector 1 or 2 |
dimensions needn’t match |
| sub(vector1, vector2) |
highest of vector 1 or 2 |
dimensions needn’t match |
| mul(vector, Number) |
Vector |
|
| div(vector, Number) |
Vector |
|
| clamp(value, limit1, limit2) |
Number |
result: limit1_value_limit2 |
| dot(vector1, vector2) |
Number |
Only uses first two dimensions of either vector |
| cross(vector1, vector2) |
Vector |
|
| normalize(vector) |
Vector |
Gives vector with same direction but length of 1 |
| length(vector) |
Number |
|
| length(from_point, to_point) |
Number |
|
| look_at(from_point, to_point) |
Vector |
Apply result to orientation, 3D only |
Interpolation Methods
These methods smoothly interpolate between the user-supplied values 1 and 2.
| linear(t,t_min, t_max,
value1, value2) |
same as value1 |
value2 will be coerced
to same dimension as value 1 |
| ease(t,t_min, t_max,
value1, value2) |
same as value1 |
value2 will be coerced
to same dimension as value 1 |
| ease_in(t,t_min, t_max,
value1, value2) |
same as value1 |
value2 will be coerced
to same dimension as value 1 |
| ease_out(t,t_min,
t_max, value1, value2) |
same as value1 |
value2 will be coerced
to same dimension as value 1 |
| note: t_min and t_max are optional; if omitted, AE will assume default range of 0 to 1. |
|
|