main/src/georegression/metric/UtilAngle.java
public static double distHalf( double angA , double angB ) {
		double a = Math.abs(angA-angB);
		if( a <= Math.PI/2 )
			return a;
		else
			return Math.PI-a;
	}
public static double distHalf( double angA , double angB ) {
		double a = Math.abs(angA-angB);
		if( a <= Math.PI/2 )
			return a;
		else
			return Math.PI-a;
	}
Angular distance between two half circle angles.

@param angA Angle between -pi/2 and pi/2.
@param angB Angle between -pi/2 and pi/2.
@return Acute angle between the two input angles.