public static double angle(Quat4d q) {
		AxisAngle4d axis = new AxisAngle4d();
		axis.set(q);
		return axis.angle;
	}
public static double angle ( Quat4d q ) { AxisAngle4d axis = new AxisAngle4d ( ) ; axis . set ( q ) ; return axis . angle ; }
Calculate the rotation angle component of the input unit quaternion.

@param q
unit quaternion Quat4d
@return the angle in radians of the input quaternion