/// Get the current joint translation, usually in meters.
public float GetJointTranslation()
{
Body b1 = _bodyA;
Body b2 = _bodyB;
Vector2 p1 = b1.GetWorldPoint(_localAnchor1);
Vector2 p2 = b2.GetWorldPoint(_localAnchor2);
Vector2 d = p2 - p1;
Vector2 axis = b1.GetWorldVector(_localXAxis1);
float translation = Vector2.Dot(d, axis);
return(translation);
}