Expressions & Snippets

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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
// Declaration
var myVariable; 
var 🍎,🍐,🍐
​
// Initialization
var fruit = 🍎;
var fruitArray = [🍏,🍎,🍐,🍊,🍋,🍌,🍉,🍇];
String
"string is text"
​
// For-Loops
for( var i = 0; i < value ; i++){
    statement
}
​
//if/else statements
if (fruit){
    statement} else {
statement}
​
    // Shorthand if statement
    if(x==1) 10; 
    
    // Using ternary operation
    condition ? exprIfTrue : exprIfFalse
    
// ternary
x = (y>=5)? 20:50; // if checkbox is true, 20 else 50
​
//Object
var x = {firstName:"John", lastName:"Doe"}; //
​
// Regular Expressions (Regex)
"\n"
​
// Single line comment
​
/* Multi-line comment
Etiam 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, myPos
distance = dst
sourceRect = s
myLayer
myNumLayers
​
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
var dst = 50;
var x= thisComp.layer(index-1).transform.position[0]+dst
;
value + [x,0]
;
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
var s = sourceRectAtTime();
​
// Top left ↖
[s.left, s.top] // 
​
// Top center ↑
[s.left, s.top] + [s.width / 2, 0];
​
// Top right ↗
[s.left, s.top] + [s.width, 0];
​
// Center left ← 
[s.left, s.top] + [0, s.height / 2];
​
// Center
[s.left, s.top] + [s.width, s.height] / 2;
​
// Center right → 
[s.left, s.top] + [s.width, s.height / 2]
​
// Bottom left ↙
​
[s.left, s.top] + [0, s.height]
​
// Bottom center ↓ 
[s.left, s.top] + [s.width / 2, s.height]
​
//Bottom right ↘
[s.left, s.top] + [s.width, s.height]
Random positioning XYZ
seed = 20;
min = [25,25,-1900]; // Connect to 3D Point Control for control
max = [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
s = [];
ps = parent.transform.scale.value;
for (i = 0; i < ps.length; i++){
s[i] = value[i]*100/ps[i];
}
s
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
target = thisComp.layer("Null 1"); // set this to the layer to aim at
p = position - target.position;
radiansToDegrees( Math.atan2( p[1], p[0] ) )- 90
target = thisComp.layer("controls"); // set this to the layer to aim at
p = thisLayer.toWorld(anchorPoint) - target.position;
radiansToDegrees(Math.atan2(p[1], p[0])) - 90
target = thisComp.layer("Null 1");// set this to the layer to aim at
lookAt( 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 segEndTime
while (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, flicker
if (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 sliders
freq = 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 sliders
freq = 1;
amp = 100;
octave = 1;
amp_mult = 3;
​
opacity = wiggle(freq, amp, octave, amp_mult, time)
​
​
// VARIABLES
minSeg = control.effect("minSeg")("Slider"); //minimum interval (must be > 0) 
maxSeg = control.effect("maxSeg")("Slider");; //maximum interval (must be > minSeg) 
​
// flickering duration
minFlicker = 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 segEndTime
while (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, flicker
if (time > segEndTime - flickerDur) {
    random(0, 100)
} else {
    opacity
}
Random opacity with sin function
// Mass flickering
vel = 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
Random opacity fade on 
v1
v2
seed = 29;
seedRandom(seed,true);
delay = random(0,1);
t = framesToTime(20) // or usethisComp.duration
​
linear(time, 0+delay,t+delay,0,100)
//VARIABLES
fadeDuration = 1;

maxDelay = .5
​
//SETUP

seedRandom(index,true);

delay = random(maxDelay);

t = time -(inPoint + delay);
​
// EXECUTION
linear(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 fill
seedRandom(index,true); // change true to 0 for constant change
random([0,0,0,1],[1,1,1,1])
Camera
​Smoothing rotation of auto-orient along path​
x-rot
y-rot
f = 2; // number of frames before and after to average
v = [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-rotation for 3d layers
​
f = 2; // number of frames before and after to average
v = [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 much
wiggle(20,30);
​
[value[0], wiggle(20,30)[1]] // wiggle y-axis only 
​
​
// Smooth wiggle — freq,amp,octave,amp_mult
wiggle(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; //frequency
amount=50;  //amplitude
wiggle(fps,amount,octaves = 1, amp_mult = 0.5,(Math.round(time*fps))/fps);
​Looping wiggle​
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=t
amp = .05;
freq = 4.0;
decay = 2.0; // springyness
n = 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"
// Variables
pad = 50;
xPad = 15;

yPad = 15;
​

seed = 1 // allow you to change between two text layers
​
// Making it work
if(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)
Carousel / Rotating layers 
/*  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 point
radius = 500
value+[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 
​
//Opacity
startVal = 0;
endVal = 100;
fadeAngle = 180;
​
v = toCompVec([0,0,1]); // layer position to comp position in Z
d = 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);
Random delayed/advanced layer playback
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 inside
seedRandom(0,true);
t= random(0,72);
framesToTime(t);
Playback at every nth frames 
n = 3 // frames
time*n
Hold and play every nth frames [source]
n = 3;  // play every __ frames
m = 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
4.Learn more
​Animoplex tutorial​
//https://gist.github.com/animoplex/cecf1c64aec4f2733ecd0edbebf4786d
Staggering animations 
// Copying animation of a layer, and start it at inPoint of layer
thisComp.layer(index+1).transform.position.valueAtTime(time-inPoint)
​
// Using delay
offset = 1;
thisComp.layer(index+1).transform.position.valueAtTime(time-offset)    
Radial scale up staggering ✅
nsc
OF
// 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)
//apply to scale
target = 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
//Create a null named "EFFECTOR" 
//Add 2 Slider Control Effects renamed to "maxDist" and "delay"
​
​
// EXECUTE
target = thisComp.layer("EFFECTOR").transform
maxDist = 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);
​
// EXECUTION
target.opacity.valueAtTime(time - delay)
​
​
​