After-Effects-Fun

After Effects Fun

Expressions, scripts and projects for Adobe After Effects.

Usually created by myself or others on the /r/AfterEffects Discord.

Projects

These were made using custom exploits!

Playable Mario (JavaScript only)

Playable Pong (JavaScript only)

Drawing (JavaScript only)

Expressions

Limitless linear

Custom easings

Spring easing

Path rotation

Spiral path

Camera snapping

Tools

Image to expression converter

Dave drawing demo

Global Variable Exploits

WARNING: These are all unpredictable to work with!

To have fun in After Effects, I often need to store data in memory and share it between expressions.

Often this is considered impossible, but there are several ways to do it:

1. Variable Leaking (JavaScript only)

I discovered variable names aren’t properly deleted by After Effects:

// Write a variable named "leak"
var leak = 5;

// Read all variable names
Object.keys(this); // ["leak"] (among others)

Variable names are shared between all expressions, and remain in memory until After Effects is restarted.

Object.keys(this) reads variable names, but not values. Therefore to store values, I put them in the name itself:

// Write a variable named "leak_5"
var leak_5;

eval() allows dynamic variable names:

// Write any variable name you want
const name = "hello";
eval(`var ${name}`);

To tell whether a variable is built-in, you can add a prefix:

// Add a "leak_" prefix to identify custom variables
const data = "hello";
eval(`var leak_${data}`);

// Read all variable names
Object.keys(this); // ["leak", "leak_5", "hello", "leak_hello"] (among others)

Using this concept, you can store multiple types of data in one variable name:

// Write 2 values into a single name
const writeX = 5;
const writeY = "hi";

eval(`var leak_${writeX}_${writeY}`);

// Read values by splitting
const parts = Object.keys(this).pop().split("_"); // ["leak", "5", "hi"]

const readX = parseInt(parts[1]); // 5
const readY = parts[2]; // "hi"

You can delete variable names like so:

// Delete variable named "leak_5_hi"
delete leak_5_hi;

Many characters aren’t allowed in variable names, so you have to be creative.

2. The Debug Object (JavaScript + ExtendScript)

@stibinator told me about the debug object $.

$ is shared between all expressions, and remains in memory until After Effects is restarted.

// Write number
$.leak = 5;

// Read number
$.leak; // 5

Object.keys works on $:

// Read all keys
Object.keys($); // [{ leak: 5 }] (among others)

$ allows any type of data to be stored:

// Write complex data
$.leak2 = [
    {
        name: "Jeff",
        age: 20
    },
    {
        name: "Joe",
        age: 1
    }
];

// Read complex data
$.leak2; // [{ name: "Jeff", age: 20 }, { name: "Joe", age: 1 }]

$ allows custom keys:

// Write using a custom key
const key = "leak3";
$[key] = 123;

// Read using a custom key
$[key]; // 123

$ also works in ExtendScript, but Object.keys doesn’t.

3. Environment Variables (ExtendScript only)

I discovered ExtendScript has a method which sets environment variables:

$.setenv(key, value);

However it only writes string values:

$.setenv("leak", 5);
$.getenv("leak"); // "5"

Summary

Exploit	Engine	Get	Set	Capable of storing
Variable leaking	JavaScript	Object.keys(this)	eval(`var ${value}`)	Strings (excluding special characters)
The debug object	Both	$.key	$.key = value	Anything
Environment variables	ExtendScript	$.getenv(key)	$.setenv(key, value)	Strings

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