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After Effects expressions

Your daily dose of expressions.

What are expressions ?

Expressions in After Effects are lines of code that allow you to create links between different layer properties and control them in a more precise and flexible way. They enable you to create more complex animations and synchronize them with other elements in the composition more efficiently.

For example, you can use an expression to make one layer's position follow another layer's, or to ensure that the value of a property, such as a layer's opacity, varies based on the audio frequency of an audio track.

Resources for learning expressions

Expressions Cheat Sheet

Expressions docs

More resources to come...

May 22, 2023

Fade a layer according to distance from the camera

Simply apply this script to the opacity of your layer, and the layer will fade as it approaches the camera. This code is useful when you want to simulate depth of field and control when your layers should fade.

 startFade = 500; // Start fade 500 pixels from camera. endFade = 1500; // End fade 1500 pixels from camera. try{ // Check whether there's a camera. C = thisComp.activeCamera.toWorld([0,0,0]); }catch(err){ // No camera, so assume 50mm. 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)

Code is not available on mobile.

May 22, 2023

"Bounding box" for a text

Here's the expression to automatically resize a text box in After Effects, which should save you a lot of time. The first expression must be applied to the size of your rectangle shape, while the second must be added to the anchor point of your rectangle shape.

/* 1 */
box=thisComp.layer("dfd").sourceRectAtTime();
Width=box.width;
Height=box.height;
p=effect("Slider Control")("Slider");
x=Width+p;
y=Height+p;
[x,y] /* 2 */
box=thisComp.layer("dfd").sourceRectAtTime();
Width=box.width;
Height=box.height;
Top=box.top;
Left=box.left;
p=effect("Slider Control")("Slider");
x=Width/-2-Left;
y=Height/-2-Top;
[x,y]

Code is not available on mobile.

May 22, 2023

Bounce on rotation

Create two key points and use this rotational bounce expression. I'd like to thank School of Motion for this script. For more details on this specific bounce expression, please visit their website.

e = .5; //elasticity
g = 1000; //gravity
nMax = 5; //number of bounces allowed
n = 0;
if (numKeys > 0){ n = nearestKey(time).index; if (key(n).time > time) n--;
}
if (n > 0){ t = time - key(n).time; v = -velocityAtTime(key(n).time - .001)*e; vl = length(v); if (value instanceof Array){ vu = (vl > 0) ? normalize(v) : [0,0,0];
}else{ vu = (v < 0) ? -1 : 1; } tCur = 0; segDur = 2*vl/g; tNext = segDur; nb = 1; // number of bounces while (tNext < t && nb <= nMax){ vl *= e; segDur *= e; tCur = tNext; tNext += segDur; nb++ } if(nb <= nMax){ delta = t - tCur; value + vu*delta*(vl - g*delta/2); }else{ value }
}else value

Code is not available on mobile.

May 22, 2023

Bounce on scale

Here's a cool way to give your layer the bouncy effect of jelly or gelatin.

timeToStart = .5; if (time > timeToStart) {
maxDev = 30; // max deviation in pixels
spd = 30; //speed of oscillation
decay = 1.0; //how fast it slows down
t = time - inPoint;
x = scale[0] + maxDev*Math.sin(spd*t)/Math.exp(decay*t);
y = scale[0]*scale[1]/x;
[x,y]
} else { value; }

Code is not available on mobile.

May 22, 2023

Trigger expression on marker

Automate actions based on the position of markers in the composition.

n=0;
if(marker.numKeys>0) { n=marker.nearestKey(time).index; if(marker.key(n).time>time) { n--; } if(n==0) { value; } else { t=time-marker.key(n).time; //time since marker //Do Stuff }
} else { value;
}

Code is not available on mobile.

May 22, 2023

Show/Hide layer with drop-down list

Apply to a layer's opacity property. Change the layer name to begin with [1,2,3] to match the drop-down parameter.

select = effect("Dropdown Control")("Menu").value;

Code is not available on mobile.

May 22, 2023

Get the date

The expression for the current date gives you immediate access to today's value.

d = new Date(Date(0));
// Format parameter
divider = "/"
yearLength = 2; // use 2 for one year AA format, 4 for AAAA format
function padZeros(n){ if(n <= 9){ return "0" + n; } return n
}
yearTrim = (yearLength===2) ? 2 : 0;
"" + padZeros(d.getMonth()+1) + divider + padZeros(d.getDate()) + divider + d.getFullYear().toString().substring(yearTrim,4);

Code is not available on mobile.

May 22, 2023

Obtain the composition's center and scale

Use the "Composition width and height" expression to center and scale a layer.

[thisComp.width,thisComp.height] * 0.5;

Code is not available on mobile.

May 22, 2023

Create a delay

The "Delay" function can be used to create a delay of a certain number of frames.

delay = 5; // number of delayed frames
d = delay*thisComp.frameDuration*(index - 1);
thisComp.layer(1).rotation.valueAtTime(time - d)

Code is not available on mobile.

May 22, 2023

Center anchor point vertically on text

Ensure that the anchor point is always vertically centered on a text layer.

y=value[1]-sourceRectAtTime(time).height/2;
[0,y]

Code is not available on mobile.

May 22, 2023

Attach a 2D position to a 3D Null

A small, powerful and versatile expression for wide-ranging possibilities.

thisComp.layer("3D Layer Name").toComp([0,0,0]);

Code is not available on mobile.

May 22, 2023

Keep the same stroke width

Expression to maintain the contour width of a shape when resizing it.

value / length(toComp([0,0]), toComp([0.7071,0.7071])) || 0.001;

Code is not available on mobile.

February 14, 2023

Timer / animated timecode

Expression to copy into your text source.

var hour = Math.floor((time/60)/60);
var min = Math.floor(time/60);
var sec = Math.floor(time);
var mili = Math.floor(time*60);
if (mili > 59){ mili = mili - sec*60; }
if (mili < 10){ mili = "0" + mili; } if (sec > 59){ sec = sec - min*60; }
if (sec < 10){ sec = "0" + sec; } if (min >= 59){ min = min - hour*60; }
if (min < 10){ min = "0" + min; }
if (hour < 10){ hour = "0" + hour; }
//Output
hour + ' : ' + min + ' : ' + sec + ' : ' + mili;

Code is not available on mobile.

February 14, 2023

Auto Fade In & Out

Make a layer appear and disappear by using an expression to define the duration.

fadeDuration = .5 ; // Set the duration of your "Fade"
fadeIn = linear(time, inPoint, inPoint + fadeDuration, 0, 100);
fadeOut = linear(time, outPoint - fadeDuration, outPoint, 0, 100);
fadeIn-fadeOut;

Code is not available on mobile.

February 14, 2023

Ignore "parent" layer rotation

A small expression to add to the rotation of the "child" layer to ignore the rotation of the "parent".

value - parent.transform.rotation

Code is not available on mobile.

February 14, 2023

Reduce the number of images

Expression that uses the "temporal posterization" effect, to be copied above the expression you wish to affect.

posterizeTime(12);
value; // (If there is one) put the rest of your expression here

Code is not available on mobile.

February 14, 2023

Block a random number

Use this expression in your text source, to generate a fixed and random number.

seedRandom(index,true);
myValue = random(50) ;

Code is not available on mobile.

February 14, 2023

Wiggle between two values

Expression that works on number value properties.

min = 0;
max = 30;
freq = 1; // Number of oscillations per second
avgVal = (min + max)/2;
amp = (max - min)/2
avgVal + amp *(Math.sin(time*freq*Math.PI*2))

Code is not available on mobile.

February 14, 2023

Typewriter effect

Expression to paste into your text source.

// Start and end variables (can be modified)
var startAt = 0; var endAt = 9; // Text part
var maxLetters = Math.floor(linear(time, startAt, endAt, 0, value.length));
var result = value.substring(0, maxLetters);
result

Code is not available on mobile.

February 14, 2023

Wiggle on X or Y

Limits the wiggle to a single dimension. This expression concerns only X to affect Y change the last line to [ value[ 0 ],w[ 1 ] ].

frequency = 2;
amplitude = 10;
w = wiggle(frequency, amplitude);
[w[0],value[1]]

Code is not available on mobile.

February 14, 2023

Checking a property with a checkbox

Use this expression for a property you want to be able to "check".

value * effect("Control Name")("Checkbox"); // replace by your checkbox effect

Code is not available on mobile.

February 14, 2023

Bounce

Use this expression to create a bounce effect.

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 && t < 1){
v = velocityAtTime(key(n).time - thisComp.frameDuration/10);
amp = .06;
freq = 3;
decay = 5.0;
value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
}else{
value;
}

Code is not available on mobile.

February 14, 2023

Create a loop

This expression is the best way to loop an animation, as it loops both the animation input and the output.

loopIn() + loopOut() - value; // You can put "pingpong" or "offset" in the brackets to suit your needs.

Code is not available on mobile.

February 14, 2023

Sin Curve

Expression to be copied into the property to which you wish to apply a deformation with a sine curve.

freq=1;
amp=50;
wind = amp*Math.sin(time*freq*2*Math.PI);
[transform.position[0],(height/2)+wind]

Code is not available on mobile.

February 14, 2023

Control the number of repetitions of your loop

Very useful when you have an end to your "loopOut".

nLoops = 10;
if (numKeys > 1){
loopDur = key(numKeys).time - key(1).time;
n = Math.floor((time - key(1).time)/loopDur);
if (n < nLoops){
t = (time - key(1).time)%loopDur;
valueAtTime(key(1).time + t);
}else{
valueAtTime(key(numKeys).time);
}
}else
value;

Code is not available on mobile.

February 5, 2023

Blink Effect

One of several solutions for creating a "blinking" effect. Paste this expression into your opacity property.

VBlink = 20;
n = Math.sin(time*VBlink);
if (n<=0) {
0;
}
else {
100;
}

Code is not available on mobile.

February 5, 2023

Random blinking

Very useful and quick to create a "neon" effect. An expression to copy into your opacity property. Simply set the opacity of the affected layer to 50% and paste the following expression:

on = 100;
off = 0;
x = wiggle(5,50)
if (x>50) onelse off

Code is not available on mobile.

February 5, 2023

Center your form repeat

Copy this expression into the offset attribute of your repeat on your shape layer. It automatically centers the repeat on the middle shape. Bonus: duplicate your repeat and reverse the axis to create a grid.

(thisProperty.propertyGroup(1).copies - 1) / -2

Code is not available on mobile.

February 5, 2023

Loop a Wiggle

Expression to be copied into the property you wish to "wiggle".

frequency = 2;
amplitude = 40;
secondsToLoop = 3; // loop duration in seconds
// --------
t = time % secondsToLoop;
wiggle1 = wiggle(frequency, amplitude, 1, 0.5, t);
wiggle2 = wiggle(frequency, amplitude, 1, 0.5, t - secondsToLoop);
linear(t, 0, secondsToLoop, wiggle1, wiggle2)/* Replace by for scale:w=linear(t, 0, secondsToLoop, wiggle1, wiggle2);
[w[0], w[0]] */

Code is not available on mobile.

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