When you add masks, effects, paint, or text to a layer, After Effects adds new properties to the Timeline panel. There are too many of these properties to list here, so use the pick whip to learn the syntax for referring to them in your expressions.

anchorPoint

Return type: Property [2 or 3].

Returns the anchor point value of the layer in the layer’s space.

position

Return type: Property [2 or 3].

Returns the position value of the layer, in world space if the layer has no parent or in the parent’s layer space if there is a parent.

scale

Return type: Property [2 or 3].

Returns the scale value of the layer, expressed as a percentage.

rotation

Return type: Property.

Returns the rotation value of the layer in degrees. For a 3D layer, it returns the z rotation value in degrees.

opacity

Return type: Property.

Returns the opacity value for the layer, expressed as a percentage.

audioLevels

Return type: Property [2].

Returns the value of the Audio Levels property of the layer, in decibels. This is a 2D value; the first value represents the left audio channel, and the second value represents the right. The value is not the amplitude of the source material’s audio track; instead, it is the value of the Audio Levels property, which may be affected by keyframes.

timeRemap

Return type: Property.

Returns the value of the Time Remap property, in seconds, if Time Remap is enabled.

marker.key(index)

Return type: MarkerKey.

Argument type: index is a Number.

Returns the MarkerKey object of the layer-time marker with the specified index.

marker.key(name)

Return type: MarkerKey.

Argument type: name is a String.

Returns the MarkerKey object of the layer-time marker with the specified name. The name value is the name of the marker, as typed in the comment field in the marker dialog box, for example, marker.key("ch1"). If more than one marker on the layer has the same name, this method returns the marker that occurs first in time (in layer time). The value for a marker key is a String, not a Number.

This expression on a property ramps the property’s value from 0 to 100 between two markers identified by name:

  m1 = marker.key("Start").time; 
  m2 = marker.key("End").time;  
  linear(time, m1, m2, 0, 100);

marker.nearestKey(t)

Return type: MarkerKey.

Argument type: t is a Number.

Returns the layer-time marker that is nearest in time to t. For example, this expression returns the time of the marker on the layer nearest to the time of 1 second:

  marker.nearestKey(1).time

This expression returns the time of the marker on the layer nearest to the current time:

  marker.nearestKey(time).time

marker.numKeys

Return type: Number.

Returns the total number of markers on the layer.

name

Return type: String.

Returns the name of the layer.