public static float Distance (Vector3 firstPosition, Vector3 secondPosition)
        {
            Vector3 heading;

            heading.x = firstPosition.x - secondPosition.x;
            heading.y = firstPosition.y - secondPosition.y;
            heading.z = firstPosition.z - secondPosition.z;

            float distanceSquared = heading.x * heading.x + heading.y * heading.y + heading.z * heading.z;
            return Mathf.Sqrt(distanceSquared);
        }

        public static float DistanceUnsquared(Vector3 firstPosition, Vector3 secondPosition)
        {
            return (firstPosition.x - secondPosition.x) * (firstPosition.x - secondPosition.x) +
                    (firstPosition.y - secondPosition.y) * (firstPosition.y - secondPosition.y) +
                    (firstPosition.z - secondPosition.z) * (firstPosition.z - secondPosition.z);
        }