update(dt) {
    dt = this._computeEaseTime(dt);
    const locFrom = this._from; const
      locTo = this._to;
    if (locFrom) {
      this.target.setAmbientLightColor({
        r: locFrom.r + (locTo.r - locFrom.r) * dt,
        g: locFrom.g + (locTo.g - locFrom.g) * dt,
        b: locFrom.b + (locTo.b - locFrom.b) * dt,
      });
    }
  }
Called once per frame. Time is the number of seconds of a frame interval.
@param {Number} dt time in seconds