# Expressions & Snippets

Here are list of useful expressions I curated and written. This page is currently being sorted into the pages under Cookbook & JSX Cheatsheet

## Transformation

### Constant Value Drift and Motion

#### 1. Linear Value Drift

``value + time * 50;``

#### 2. Apply Value Drift to Array Element eg. Position

``value + [time * 50, 0];``

#### 3. Offset Value Change

``value + (time - inPoint) * 50;``

4. Constant Horizontal Motion

``````x = position[0] + (time - inPoint) * (-10);
y = position[1];
[x, y]``````

### X-Axis

``````var xOffset = 350;
var prevLayerX = thisComp.layer(index - 1).transform.position[0];
[xOffset + prevLayerX, value[1]];
``````

### Y-Axis

``````var yOffset = 350;
var prevLayerY = thisComp.layer(index - 1).transform.position[1];
[value[0], yOffset + prevLayerY];
``````

### 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 for randomization
var seed = 20;

// Define the minimum values for randomization
var minX = 25;
var minY = 25;
var minZ = -1900;

// Define the maximum values for randomization
var maxX = thisComp.width;
var maxY = thisComp.height;
var maxZ = 50;

// Set the random seed
seedRandom(seed, true);

// Generate random values within the defined ranges
var randomX = random(minX, maxX);
var randomY = random(minY, maxY);
var randomZ = random(minZ, maxZ);

// Create an array with the random values
[randomX, randomY, randomZ];
``````

Alternatively, you can use array variables for a preferred and shorter expression.

``````// Seed for randomization
var seed = 20;

// Define the minimum and maximum values for randomization
var minValues = [25, 25, -1900];
var maxValues = [thisComp.width, thisComp.height, 50];

// Set the random seed
seedRandom(seed, true);

// Create an array with the random values
random(minValues,maxValues)
``````

## Scale

### Maintain Scale When Parented

``````var scaleFactor = [];
var parentScale = parent.transform.scale.value;

for (var i = 0; i < parentScale.length; i++) {
scaleFactor[i] = (value[i] * 100) / parentScale[i];
}

scaleFactor;``````

Implementation

## Rotation

### Aim constraint by Kevin Camp / Dan Ebberts

``````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``````

### Retrieving auto-orientation rotation value

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

### 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;
value+orient+180
}catch(err){value}``````

### Ignore Parent 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``````

``````seed = 29;
seedRandom(seed,true);
delay = random(0,1);
t = framesToTime(20) // or usethisComp.duration

linear(time, 0+delay,t+delay,0,100)``````

### Distance-based opacity fade by Animoplex

``````// Distance Based Opacity Fade

try {
C = thisComp.activeCamera.toWorld([0,0,0]);
} catch(err) {
w = thisComp.width * thisComp.pixelAspect;
C = [0,0,-z];
}
P = toWorld(anchorPoint);
d = length(C, P);

### 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 Color Controls
seed = 20;
seedRandom(seed,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

``````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]);

// turn off auto-orient``````

## 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);``````

### 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

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);

### 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 point

// 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;

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;
``````

#### 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 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

``//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 ✅

``````// 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)``````

### Effector opacity fade on ✅

``````//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)``````

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