Adobe After Effects Expression Cheat Sheet

Table Of Contents

• Globals
  • Contextual
    • Objects
    • Project
  • Static
    • Functions
    • Time Conversion
    • Locating Project Elements

Globals

Contextual Variables

Objects

Object	Description	Example
thisComp	Current composition	thisComp;
thisLayer	Current layer	thisLayer.transform.scale[1];
thisProperty	Current property the expression is applied upon.	thisProperty[1];
time	Current timecode at cursor position in seconds.	"Seconds: " + time;
value	Current value associated to the current property.	value + "_TEST";

Project

Object	Description	Example
colorDepth	Project color depth in bits per pixel.	colorDepth;

Composition Object Properties & Functions

Function	Description
layer(index || number)	Returns a Layer, Light or Camera object.
layer(layer, relIndex)	Returns the object with a relative index to the given layer.

Functions

Time Conversion

Function	Description	Example
framesToTime(frames, fps)	Convert frames to timecode in seconds.	framesToTime(50, 1.0 / thisComp.frameDuration);
timeToCurrentFormat(t, fps, isDuration)	Converts timecode to the current Project Settings display format.
timeToFeetAndFrames(t, fps, framesPerFoot, isDuration)	Converts timecode to feet and frames format.
timeToFrames(t, fps, isDuration)	Converts timecode to frames.
timeToNTSCTimecode(t, ntscDropFrame, isDuration)	Converts timecode to NTSC timecode with or without drop frame.
timeToTimecode(t, timecodeBase, isDuration)	Converts timecode to other timecode using the given timebase.

Locating Project Elements

Function	Description	Example
comp(name)	Find the open composition with the given name.	comp("Comp 1");
footage(name)	Find the project footage with the given name.	footage("RedHarring.png");

Tips & Tricks

Set Size And Position Of Shape To Text

You have:

• Text Layer
• Shape Layer

You want to:

• Set the shape to the size and position of the text.

Solution:

Let's say you have a shape layer with a rectangle shape.

1. Set the rectangle layer's parent to the text layer This will make the positioning relative to the text layer's positioning.

2. Add following expression to the rectangle path's size property

var textLayer = thisComp.layer("Text Layer 1");
var textRect = textLayer.sourceRectAtTime(time - textLayer.inPoint, true);

// set size of rectangle path to text rectangle's width and height
[textRect.width, textRect.height];

This will set the size of the rectangle to the size of the text. When there are multiple lines, it takes the full size of all lines.

3. Add following expression to the rectangle path's position property

var rectPath = content("Rectangle 1").content("Rectangle Path 1");
var x = rectPath.size[0];
var y = rectPath.size[1];

// set position of rectangle path to text rectangle's width and height
[x/2, -(y/2)];

This sets the bottom left position of the rectangle's path to top left of the layer. Text Layers always have their anchor points on the bottom left of the first line of text. This will make the calculation more easy to do.

4. Add following expression to the rectangle layer's Transform.Position property

var textLayer = thisComp.layer("Text Layer 1");
var textRect = textLayer.sourceRectAtTime(time - textLayer.inPoint, true);
[ textLayer.transform.position[0] + textRect.left,
  textLayer.transform.position[1] + textRect.top + textRect.height ];

This sets the position of the rectangle's layer to the position of the text. The reason for adding the rectangle size, is because the font rendering can cause the first letter to be a few pixels off the position. Adding the rectangle coordinates will compensate for that.

Problems:

• The text has multiple lines, and you want a rectangle for each line instead of one covering all the lines.
• The text has letters that extend the rectangle on the bottom (like the letter q)

Add Interlacing Jitter

You Have:

• Video Layer

You Want To:

Add horizontal jitter to the video so that it looks like 50 hz interlacing.

Solution:

1. Add following expression to the video layer's Transform.Position property

[transform.position[0], transform.position[1] + ((timeToFrames(time) % 2) * 2)]

Problems:

• The jitter is too heavy You can solve this by removing the multiplication in the expression

  [transform.position[0], transform.position[1] + (timeToFrames(time) % 2)]

  Or even multiple it by half to get a very subtle shake.

  [transform.position[0], transform.position[1] + ((timeToFrames(time) % 2) * 0.5)]

• The text needs to be vertically centered. Add the following expression to the text layer's Transform.Position property

  S = thisLayer;
  x =transform.position[0];
  y =transform.position[1];
  rect =S.sourceRectAtTime(time,false);
  y_offset = rect.height/2;
  [x,y-y_offset]