setFromEuler( euler, update = true ) {

		const x = euler._x, y = euler._y, z = euler._z, order = euler._order;

		// http://www.mathworks.com/matlabcentral/fileexchange/
		// 	20696-function-to-convert-between-dcm-euler-angles-quaternions-and-euler-vectors/
		//	content/SpinCalc.m

		const cos = Math.cos;
		const sin = Math.sin;

		const c1 = cos( x / 2 );
		const c2 = cos( y / 2 );
		const c3 = cos( z / 2 );

		const s1 = sin( x / 2 );
		const s2 = sin( y / 2 );
		const s3 = sin( z / 2 );

		switch ( order ) {

			case 'XYZ':
				this._x = s1 * c2 * c3 + c1 * s2 * s3;
				this._y = c1 * s2 * c3 - s1 * c2 * s3;
				this._z = c1 * c2 * s3 + s1 * s2 * c3;
				this._w = c1 * c2 * c3 - s1 * s2 * s3;
				break;

			case 'YXZ':
				this._x = s1 * c2 * c3 + c1 * s2 * s3;
				this._y = c1 * s2 * c3 - s1 * c2 * s3;
				this._z = c1 * c2 * s3 - s1 * s2 * c3;
				this._w = c1 * c2 * c3 + s1 * s2 * s3;
				break;

			case 'ZXY':
				this._x = s1 * c2 * c3 - c1 * s2 * s3;
				this._y = c1 * s2 * c3 + s1 * c2 * s3;
				this._z = c1 * c2 * s3 + s1 * s2 * c3;
				this._w = c1 * c2 * c3 - s1 * s2 * s3;
				break;

			case 'ZYX':
				this._x = s1 * c2 * c3 - c1 * s2 * s3;
				this._y = c1 * s2 * c3 + s1 * c2 * s3;
				this._z = c1 * c2 * s3 - s1 * s2 * c3;
				this._w = c1 * c2 * c3 + s1 * s2 * s3;
				break;

			case 'YZX':
				this._x = s1 * c2 * c3 + c1 * s2 * s3;
				this._y = c1 * s2 * c3 + s1 * c2 * s3;
				this._z = c1 * c2 * s3 - s1 * s2 * c3;
				this._w = c1 * c2 * c3 - s1 * s2 * s3;
				break;

			case 'XZY':
				this._x = s1 * c2 * c3 - c1 * s2 * s3;
				this._y = c1 * s2 * c3 - s1 * c2 * s3;
				this._z = c1 * c2 * s3 + s1 * s2 * c3;
				this._w = c1 * c2 * c3 + s1 * s2 * s3;
				break;

			default:
				console.warn( 'THREE.Quaternion: .setFromEuler() encountered an unknown order: ' + order );

		}

		if ( update === true ) this._onChangeCallback();

		return this;

	}
Sets this quaternion from the rotation specified by the given
Euler angles.

@param {Euler} euler - The Euler angles.
@param {boolean} [update=true] - Whether the internal `onChange` callback should be executed or not.
@return {Quaternion} A reference to this quaternion.