# Expressions & Snippets

Last update : 24 April 2021

# Abstract

Here are list of useful expressions I curated and written.

⚠️This page is currently being sorted into the pages under Cookbook, so some expressions that you usually reference here has been moved to those pages.

# Javascript basics

// Declarationvar myVariable; var 🍎,🍐,🍐​// Initializationvar fruit = 🍎;var fruitArray = [🍏,🍎,🍐,🍊,🍋,🍌,🍉,🍇];String"string is text"​// For-Loopsfor( var i = 0; i < value ; i++){    statement}​//if/else statementsif (fruit){    statement} else {statement}​    // Shorthand if statement    if(x==1) 10;         // Using ternary operation    condition ? exprIfTrue : exprIfFalse    // ternaryx = (y>=5)? 20:50; // if checkbox is true, 20 else 50​//Objectvar x = {firstName:"John", lastName:"Doe"}; //​// Regular Expressions (Regex)"\n"​// Single line comment​/* Multi-line commentEtiam aliquet et mi quis tempor. Nulla ullamcorper, sapien in molestie rhoncus, justo magna molestie dolor, Nullam dignissim interdum mi sit a */​

## Preferred shorthand for naming variables

velocity = v or vel  multiplier = mul;position = pos, myPosdistance = dstsourceRect = smyLayermyNumLayers​target = tgt

## Good practice

• Declare variable before loop statements

# Transformation

## Constant value change using Time (drifting)

time*50;​// for adding to an alement in an array such as position:value + [time*50,0]​// for value change to start at inPoint(time-inPoint)*50​// Throw (move at a constant speed without keyframes)veloc = -10; //horizontal velocity (pixels per second)x = position[0] + (time - inPoint) *veloc;y = position[1];[x,y]

## Align to X-axis or Y-axis

basic
if X or Y
basic
var dst = 50;var x= thisComp.layer(index-1).transform.position[0]+dst
;value + [x,0]
;
if X or Y
var xy = 0;var dst = 50;var x= thisComp.layer(index-1).transform.position[0]+dst
;var x= thisComp.layer(index-1).transform.position[0]+dst
xy==0? value+[x,0]: value+[0,y]; // Ternary conditional operator

## Changing anchor point

//Top lefts=sourceRectAtTime();
[0,0];// or [s.left,s.top] or [s.left,0]     // Return original position        s=sourceRectAtTime();

value-[s.width/2,s.height/2];​// ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑s=sourceRectAtTime();[0,s.top+s.height/2]​// Top rights=sourceRectAtTime();

[s.width,s.top];​// ← ← ← ← ← s=sourceRectAtTime();[s.left,0]// or [[s.left,s.height/2]​// Centers=sourceRectAtTime();[s.left+s.width/2,s.top+s.height/2]​// → → → → → s=sourceRectAtTime();[s.width,s.height/2]​// Bot lefts=sourceRectAtTime();[s.left,s.height];​// ↓ ↓ ↓ ↓ ↓ s=sourceRectAtTime();[s.width/2,s.height];​//Bot rights=sourceRectAtTime();[s.width,s.height];

## Random positioning XYZ

seed = 20;min = [25,25,-1900]; // Connect to 3D Point Control for controlmax = [thisComp.width,thisComp.height,50]​seedRandom(seed,true);​random(min,max);​// This is same as this​// x= random(min[0],max[0]);// y= random(min[1],max[1]);// z= random(min[2],max[2]);​//[x,y,z]

# Scale

## Maintain Scale When Parented

both axis
uniform
both axis
s = [];ps = parent.transform.scale.value;for (i = 0; i < ps.length; i++){s[i] = value[i]*100/ps[i];}s
uniform
arr = value;ps = parent.transform.scale.value;ratio = 100/ ps[0];​arr*ratio;

# Rotation

## ​Aim constraint by Kevin Camp / Dan Ebberts

no parent
w/ parent
3D layers
no parent
target = thisComp.layer("Null 1"); // set this to the layer to aim atp = position - target.position;radiansToDegrees( Math.atan2( p[1], p[0] ) )- 90
w/ parent
target = thisComp.layer("controls"); // set this to the layer to aim atp = thisLayer.toWorld(anchorPoint) - target.position;radiansToDegrees(Math.atan2(p[1], p[0])) - 90
3D layers
target = thisComp.layer("Null 1");// set this to the layer to aim atlookAt( position, target.position )

## ​Retrieving auto-orientation rotation value​

L = thisComp.layer("Null 1");v = L.toWorldVec([1,0]);radiansToDegrees(Math.atan2(v[1],v[0]))

## Auto-orient along path by Videolancer​

try{cornerEase = 3;p = transform.position;t = Math.min(Math.max(time,p.key(1).time+.001),p.key(p.numKeys).time);pre = position.valueAtTime(t-thisComp.frameDuration*cornerEase);post = position.valueAtTime(t+thisComp.frameDuration*cornerEase);delta = post-pre;orient = radiansToDegrees(Math.atan2(delta[0],-delta[1]));value+orient+180}catch(err){value}

# Parent

## Avoid inhering rotation

value – parent.transform.rotation

# Opacity ✅

## Flickering / Strobe

// VARIABLES    minSeg = 1.5; //minimum interval (must be > 0)     maxSeg = 2.5; //maximum interval (must be > minSeg)         // flickering duration    minFlicker = .5; //must be less than minSeg     maxFlicker = 1; // must be less than minSeg     flickerDur = random(minFlicker,maxFlicker);        //initial conditions    segEndTime = 0;     i = 1; ​// Continuous loop: create a fixed random segment value and add to segEndTimewhile (time >= segEndTime){     i += 1;     seedRandom(i,true);     segEndTime = segEndTime + random(minSeg,maxSeg); } ​// Switch back to use the current time as input to the random seed.seedRandom(1,false); ​// As time > threshold, flickerif (time > segEndTime - flickerDur){random(0,100) }else{ 100 }​// Source: http://www.motionscript.com/expressions-lab-ae65/swinging-light.html// Also see: http://www.motionscript.com/mastering-expressions/random-3.html

## Random opacity wiggle

// control = thisComp.layer("control"); // connect to null layer with slidersfreq = 1;amp = 100;octave = 1;amp_mult = 3;​wiggle(freq, amp, octave, amp_mult, time)

## Random opacity wiggle with flicker

// control = thisComp.layer("control"); // connect to null layer with slidersfreq = 1;amp = 100;octave = 1;amp_mult = 3;​opacity = wiggle(freq, amp, octave, amp_mult, time)​​// VARIABLESminSeg = control.effect("minSeg")("Slider"); //minimum interval (must be > 0) maxSeg = control.effect("maxSeg")("Slider");; //maximum interval (must be > minSeg) ​// flickering durationminFlicker = control.effect("minFlicker")("Slider");; //must be less than minSeg maxFlicker = control.effect("maxFlicker")("Slider");; // must be less than minSeg flickerDur = random(minFlicker, maxFlicker);​//initial conditions segStartTime = 0;segEndTime = 0;i = 1;​// Continuous loop: create a fixed random segment value and add to segEndTimewhile (time >= segEndTime) {    i += 1;    seedRandom(i, true);    segStartTime = segEndTime;    segEndTime = segEndTime + random(minSeg, maxSeg);}​// Switch back to use the current time as input to the random seed.seedRandom(1, false);​// As time moves threshold, flickerif (time > segEndTime - flickerDur) {    random(0, 100)} else {    opacity}

## Random opacity with sin function

// Mass flickeringvel = 50;seedRandom(0,true);Math.sin(time*vel+random(index))*100;
// 'Wave flickering'vel = 50;seedRandom(0,true);Math.sin(time*vel+index)*100;
​// Combining bool = 1
;vel = 50;
seedRandom(0,true);
wave=Math.sin(time*vel+index)*100;
rand =Math.sin(time*vel+random(index))*100;

bool==0 ? wave : rand;

## Random opacity turn on

seed = 29;threshold = linear(time,0,thisComp.duration,0,100); // or Connect to slider to animate switch on & off​seedRandom(seed,true);randValue = random(0,90);​if(randValue < threshold){    100;} else 0

v1
v2
v1
seed = 29;seedRandom(seed,true);delay = random(0,1);t = framesToTime(20) // or usethisComp.duration​linear(time, 0+delay,t+delay,0,100)
v2
//VARIABLESfadeDuration = 1;
maxDelay = .5​//SETUP
seedRandom(index,true);
delay = random(maxDelay);
t = time -(inPoint + delay);
​// EXECUTIONlinear(t,0,fadeDuration,0,100);

## Distance-based opacity fade by Animoplex

// Distance Based Opacity Fade// Original: https://helpx.adobe.com/after-effects/using/expression-examples.html// Full Tutorial: https://www.youtube.com/watch?v=I-Acdl_l9G0&t=14s​startFade = 500;endFade = 3000;try {    C = thisComp.activeCamera.toWorld([0,0,0]);} catch(err) {    w = thisComp.width * thisComp.pixelAspect;    z = (w / 2)/Math.tan(degreesToRadians(19.799));    C = [0,0,-z];}P = toWorld(anchorPoint);d = length(C, P);linear(d, startFade, endFade, 100, 0)

## Transparent backside of 3D layer

if (toCompVec([0, 0, 1])[2] > 0 ) value else 0

# Colour

## ​Hexcode from text to color​

txt = thisComp.layer("Text").text.sourceText;c = parseInt(txt,16);r = c >> 16;g = (c & 0x00ff00) >> 8;b = c & 0xff;[r,g,b,255]/255

## Random fill

// Apply on fillseedRandom(index,true); // change true to 0 for constant changerandom([0,0,0,1],[1,1,1,1])

# Camera

## ​Smoothing rotation of auto-orient along path​

x-rot
y-rot
x-rot
f = 2; // number of frames before and after to averagev = [0,0];for (i = -f; i <= f; i++){v += position.velocityAtTime(i*thisComp.frameDuration + time);}v /= (f*2+1);a = Math.atan2(v[1],v[0]);radiansToDegrees(a)​// turn off auto-orient
y-rot
//y-rotation for 3d layers​f = 2; // number of frames before and after to averagev = [0, 0, 0];for (i = -f; i <= f; i++) {    v += position.velocityAtTime(i * thisComp.frameDuration + time);}v /= (f * 2 + 1);a = Math.atan2(v[0], v[2]);radiansToDegrees(a)

# Motion

## Wiggle

// frequency by amplitude = how fast by how muchwiggle(20,30);​[value[0], wiggle(20,30)[1]] // wiggle y-axis only ​​// Smooth wiggle — freq,amp,octave,amp_multwiggle(20,30,1,2,time)​​// Jumpy Wiggle 1 (moves at a random FPS) Makes wiggle skip and hold rather than move fluidly.​v=wiggle(5,50);if(v < 50)v=0;if(v > 50)v=100;v;​// Jumpy Wiggle 2 (moves at a defined FPS)fps=5; //frequencyamount=50;  //amplitudewiggle(fps,amount,octaves = 1, amp_mult = 0.5,(Math.round(time*fps))/fps);

## Inertial Bounce / Overshoot

// Inertial Bounce (moves settle into place after bouncing around a little)// // Source: https://forums.creativecow.net/docs/forums/post.php?forumid=227&postid=19145&univpostid=19145&pview=tamp = .05;freq = 4.0;decay = 2.0; // springynessn = 0;if (numKeys > 0){n = nearestKey(time).index;if (key(n).time > time){n--;}}if (n == 0){t = 0;}else{t = time - key(n).time;}​if (n > 0){v = velocityAtTime(key(n).time - thisComp.frameDuration/10);​value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);}else{value;}

## Constant move in either x or y axis / Random walker

WIP---choice = Math.floor(random(0,2));seedRandom(0,false);stepx = random(0,50);stepy = random(0,20);if(choice ==0){	value + [stepx,0];} else if( choice ==1){	value +[0,stepy];}

# Responsive Systems / Setups

## Dynamic-sizing text box / lower-third (depreciated, see new code)

// Create two text layers named "DATA1" & "DATA2"// Variablespad = 50;xPad = 15;
seed = 1 // allow you to change between two text layers​// Making it workif(seed==1){
src = thisComp.layer("DATA1")    }else {
src = thisComp.layer("DATA2")
};
​box = src.sourceRectAtTime(time-src.inPoint);
[box.width + pad + xPad, box.height+pad +yPad];

## Slider with center fade on

v = transform.position[0] // x
d = length(v,thisComp.width/2);
maxDist= 960;​
ease(d,0,maxDist,100,0)

/*  There needs to be two layers named 'startCard' & 'endCard'    This allows rotation value to dynamically change when layers are inserted or removed.    All duplicates need to be placed within these two layers*/​//anchor pointradius = 500value+[0,0,radius]​// Y rotation​startIndex=thisComp.layer("startCard").index;
endIndex = thisComp.layer("endCard").index;numpt = startIndex-endIndex+1; // total number of layers

myIndex = index-startIndex;

angle = 360/numpt​
myIndex*angle+

## Linking layers' rotation with opacity

### Using distance & vector position

// Make sure there is a camera ​//OpacitystartVal = 0;endVal = 100;fadeAngle = 180;​v = toCompVec([0,0,1]); // layer position to comp position in Zd = length(toWorld(anchorPoint),thisComp.layer("Camera 1").toWorld([0,0,0]));c = v[2]/d;ease(c,Math.cos(degreesToRadians(fadeAngle)),1.0,startVal,endVal)​

### Using rotation

angle = transform.yRotation%360;minAngle = 0;maxAngle = 360;mid = (maxAngle+minAngle)/2;if (angle < mid)  linear(angle,minAngle,mid,100,0)else  linear(angle,mid,maxAngle,0,100)

# Time Remapping / Playback ✅

## Random frame playback

// Source Dan Ebbert​fr = 12; // frame rate;​numFrames = 8;​seedRandom(index,true);​seg = Math.floor(time*fr);​f = Math.floor(random(numFrames));​for (i = 0; i < seg; i++)​  f = (f + Math.floor(random(1,numFrames)))%numFrames;​framesToTime(f);

seedRandom(index,true);myDelay = random(1,10);time + myDelay;

## Play one frame at a time (without 'float time')

fps = 1;
x = framesToTime(Math.round(time*fps))//There probably is a better way but I cannot figured it out right now.

## Random still frame (Good for spriting)

//Apply this to a composition with a image sequence insideseedRandom(0,true);
t= random(0,72);
framesToTime(t);

## Playback at every nth frames

n = 3 // framestime*n

## Hold and play every nth frames [source]

n = 3;  // play every __ framesm = 3; // hold each frame ___ times ​f= timeToFrames(timeRemap);​p=Math.floor(f/m);​framesToTime(p*n);

# Triggering animations with marker

### Workflow

1. Create a preComp with all the different types of animation

2. In the main Comp, put an expression on the time remapping of that preComp

3. Add markers to trigger animations

//https://gist.github.com/animoplex/cecf1c64aec4f2733ecd0edbebf4786d

# Staggering animations

// Copying animation of a layer, and start it at inPoint of layerthisComp.layer(index+1).transform.position.valueAtTime(time-inPoint)​// Using delayoffset = 1;thisComp.layer(index+1).transform.position.valueAtTime(time-offset)

## Radial scale up staggering ✅

nsc
OF
nsc
// VARIABLES + SETUP
target = thisComp.layer("master").transform.scale;
maxDist = 1000;
maxDelay = 1;
​dst = length(transform.position,[thisComp.width/2,thisComp.height/2]);
delay = linear(dst,0,maxDist,0,maxDelay);​

// EXECUTION
target.valueAtTime(time-delay)

OF
//apply to scaletarget = thisComp.layer("fade");fade = target.effect("scale")(1);delay = target.effect("delay")(1)*thisComp.frameDuration;dist = length(thisLayer.toWorld(thisLayer.anchorPoint), target.toWorld(target.anchorPoint));seed = seedRandom(15, true)randomRange = target.effect("random")("Slider");rand = (random(-randomRange, randomRange))*thisComp.frameDuration;offset = delay/dist;s = fade.valueAtTime(time - offset - rand);[s,s]

## Effector opacity fade on ✅

nsc
OF
nsc
//Create a null named "EFFECTOR" //Add 2 Slider Control Effects renamed to "maxDist" and "delay"​​// EXECUTEtarget = thisComp.layer("EFFECTOR").transformmaxDist = thisComp.layer("EFFECTOR").effect("maxDist")("Slider");maxDelay = thisComp.layer("EFFECTOR").effect("delay")("Slider");​dst = length(transform.position, target.position);delay = linear(dst, 0, maxDist, 0, maxDelay);​// EXECUTIONtarget.opacity.valueAtTime(time - delay)
OF
​​