public cpDampedRotarySpring(cpBody a, cpBody b, float restAngle, float stiffness, float damping)
            : base(a, b)
        {
            this.restAngle = restAngle;
            this.stiffness = stiffness;
            this.damping   = damping;

            this.springTorqueFunc = defaultSpringTorque;

            this.target_wrn = 0.0f;
            this.w_coef     = 0.0f;
            this.iSum       = 0.0f;
        }
 public void SetSpringTorqueFunc(cpDampedRotarySpringTorqueFunc springTorqueFunc)
 {
     this.springTorqueFunc = springTorqueFunc;
 }