docs: function parentsMatrix(e, focusingCamera) {
  		if (e.parent && e.parent.getMatrix) {
  			var m1 = e.parent.getMatrix();
  			var m2 = parentsMatrix(e.parent, focusingCamera);
  			if (m2) {
  				return m1.multiplyNew(m2);
  			}
  			return m1;
  		} else {
  			if (focusingCamera) {
  				return focusingCamera.getMatrix();
  			}
  			return undefined;
  		}
  	}