Box2DX.Dynamics.PulleyJoint.SolveVelocityConstraints C# (CSharp) Method

        internal override void SolveVelocityConstraints(TimeStep step)
        {
            Body b1 = _body1;
            Body b2 = _body2;

            Vector2 r1 = b1.GetTransform().TransformDirection(_localAnchor1 - b1.GetLocalCenter());
            Vector2 r2 = b2.GetTransform().TransformDirection(_localAnchor2 - b2.GetLocalCenter());

            if (_state == LimitState.AtUpperLimit)
            {
                Vector2 v1 = b1._linearVelocity + r1.CrossScalarPreMultiply(b1._angularVelocity);
                Vector2 v2 = b2._linearVelocity + r1.CrossScalarPreMultiply(b2._angularVelocity);

                float Cdot = -Vector2.Dot(_u1, v1) - _ratio * Vector2.Dot(_u2, v2);
                float impulse = _pulleyMass * (-Cdot);
                float oldImpulse = _impulse;
                _impulse = Box2DX.Common.Math.Max(0.0f, _impulse + impulse);
                impulse = _impulse - oldImpulse;

                Vector2 P1 = -impulse * _u1;
                Vector2 P2 = -_ratio * impulse * _u2;
                b1._linearVelocity += b1._invMass * P1;
                b1._angularVelocity += b1._invI * r1.Cross(P1);
                b2._linearVelocity += b2._invMass * P2;
                b2._angularVelocity += b2._invI * r2.Cross(P2);
            }

            if (_limitState1 == LimitState.AtUpperLimit)
            {
                Vector2 v1 = b1._linearVelocity + r1.CrossScalarPreMultiply(b1._angularVelocity);

                float Cdot = -Vector2.Dot(_u1, v1);
                float impulse = -_limitMass1 * Cdot;
                float oldImpulse = _limitImpulse1;
                _limitImpulse1 = Box2DX.Common.Math.Max(0.0f, _limitImpulse1 + impulse);
                impulse = _limitImpulse1 - oldImpulse;

                Vector2 P1 = -impulse * _u1;
                b1._linearVelocity += b1._invMass * P1;
                b1._angularVelocity += b1._invI * r1.Cross(P1);
            }

            if (_limitState2 == LimitState.AtUpperLimit)
            {
                Vector2 v2 = b2._linearVelocity + r2.CrossScalarPreMultiply(b2._angularVelocity);

                float Cdot = -Vector2.Dot(_u2, v2);
                float impulse = -_limitMass2 * Cdot;
                float oldImpulse = _limitImpulse2;
                _limitImpulse2 = Box2DX.Common.Math.Max(0.0f, _limitImpulse2 + impulse);
                impulse = _limitImpulse2 - oldImpulse;

                Vector2 P2 = -impulse * _u2;
                b2._linearVelocity += b2._invMass * P2;
                b2._angularVelocity += b2._invI * r2.Cross(P2);
            }
        }