code: function blur(progress) {
    var to = (this.options.to !== undefined) ? this.options.to : 0;
    var from = (this.options.from !== undefined) ? this.options.from : 0;
    var amount = (to - from) * progress + from;
  
    this.element.style.filter = 'blur(' + amount + 'px)';
  }
docs: Update an element's blur.
  @param {Float} progress  Current progress of the scene, between 0 and 1.
  @this {Object}
  @return {void}