lerp = (start, end, amount, renderable) => {
  let dt = K / globals.defaults.frameRate;
  if (renderable !== false) {
    const ticker = /** @type Renderable */
                   (renderable) ||
                   (engine._hasChildren && engine);
    if (ticker && ticker.deltaTime) {
      dt = ticker.deltaTime;
    }
  }
  const t = 1 - Math.exp(-amount * dt * .1);
  return !amount ? start : amount === 1 ? end : (1 - t) * start + t * end;
}
https://www.rorydriscoll.com/2016/03/07/frame-rate-independent-damping-using-lerp/
@param  {Number} start
@param  {Number} end
@param  {Number} amount
@param  {Renderable|Boolean} [renderable]
@return {Number}