Trigger-based shake effect from musicvid.org

cameraShake.js

class TriggerBasedShake {
  constructor(
    returnSpeed = 0.1,
    displacementThreshold = 4,
    waveDuration = Math.PI/8,
    movementAmount = 1,
    maxShakeIntensity = 1,
    maxShakeDisplacement = 4,
    minShakeScalar = 0.9,
    maxShakeScalar = 1.6,
    minShakeAmount = 0.2
  ) {
    this.returnSpeed = returnSpeed;
    this.sumShakeX = 0;
    this.sumShakeY = 0;
    this.movementAmount = movementAmount;
    this.waveSpeedX = 1;
    this.waveSpeedY = 1;
    this.waveFrameX = 0;
    this.waveFrameY = 0;
    this.waveAmplitudeX = 1;
    this.waveAmplitudeY = 1;
    this.trigX = Math.round(Math.random());
    this.trigY = Math.round(Math.random());
    this.waveDuration = waveDuration;
    this.maxShakeIntensity = maxShakeIntensity;
    this.maxShakeDisplacement = maxShakeDisplacement;
    this.minShakeScalar = minShakeScalar;
    this.maxShakeScalar = maxShakeScalar;
    this.minShakeAmount = minShakeAmount;
  }
  
  shake (intensity) {
    let step = this.maxShakeIntensity * intensity;
    this.waveFrameX += step * this.waveSpeedX;

    if (intensity <= this.minShakeAmount) {
        if (Math.abs(this.sumShakeX) > this.displacementThreshold) {
            const l = this.sumShakeX > 0 ? -1 : 1;
            this.sumShakeX += this.returnSpeed * l;
        }
        if (Math.abs(this.sumShakeY) > 0) {
            const l = this.sumShakeY > 0 ? -1 : 1;
            this.sumShakeY += this.returnSpeed * l;
        }
    }
    if (Math.abs(this.waveFrameX) > this.waveDuration) {
        this.waveFrameX = 0;
        this.waveAmplitudeX =
            this.random(this.minShakeScalar, this.maxShakeScalar) *
            this.direction(this.sumShakeX);
        this.waveSpeedX =
            this.random(this.minShakeScalar, this.maxShakeScalar) *
            this.direction(this.sumShakeX);
        this.trigX = Math.round(Math.random());
    }
    this.waveFrameY += step * this.waveSpeedY;
    if (Math.abs(this.waveFrameY) > this.waveDuration) {
        this.waveFrameY = 0;
        this.waveAmplitudeY =
            this.random(this.minShakeScalar, this.maxShakeScalar) *
            this.direction(this.sumShakeY);
        this.waveSpeedY =
            this.random(this.minShakeScalar, this.maxShakeScalar) *
            this.direction(this.sumShakeY);
        this.trigY = Math.round(Math.random());
    }

    let trigFuncX = this.trigX === 0 ? Math.cos : Math.sin;
    let trigFuncY = this.trigY === 0 ? Math.cos : Math.sin;

    let dx =
        trigFuncX(this.waveFrameX) *
        this.maxShakeDisplacement *
        this.waveAmplitudeX *
        intensity *
        this.movementAmount;
    let dy =
        trigFuncY(this.waveFrameY) *
        this.maxShakeDisplacement *
        this.waveAmplitudeY *
        intensity *
        this.movementAmount;
    this.sumShakeX += dx;
    this.sumShakeY += dy;
  }
  
  random(min, max) {
    return Math.random() * (max - min) + min;
  }
  
  direction (cur) {
    let d = cur > 0 ? 1 : -1;
    const pull = d * Math.pow(Math.abs(cur), 0.08);
    const dir = pull + Math.random();
    return dir > 1.0 ? -1 : 1;
  }
}