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diff --git a/Source/external/Box2D/Dynamics/Joints/b2FrictionJoint.h b/Source/external/Box2D/Dynamics/Joints/b2FrictionJoint.h
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+/*
+* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_FRICTION_JOINT_H
+#define B2_FRICTION_JOINT_H
+
+#include "Box2D/Dynamics/Joints/b2Joint.h"
+
+/// Friction joint definition.
+struct b2FrictionJointDef : public b2JointDef
+{
+	b2FrictionJointDef()
+	{
+		type = e_frictionJoint;
+		localAnchorA.SetZero();
+		localAnchorB.SetZero();
+		maxForce = 0.0f;
+		maxTorque = 0.0f;
+	}
+
+	/// Initialize the bodies, anchors, axis, and reference angle using the world
+	/// anchor and world axis.
+	void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);
+
+	/// The local anchor point relative to bodyA's origin.
+	b2Vec2 localAnchorA;
+
+	/// The local anchor point relative to bodyB's origin.
+	b2Vec2 localAnchorB;
+
+	/// The maximum friction force in N.
+	float32 maxForce;
+
+	/// The maximum friction torque in N-m.
+	float32 maxTorque;
+};
+
+/// Friction joint. This is used for top-down friction.
+/// It provides 2D translational friction and angular friction.
+class b2FrictionJoint : public b2Joint
+{
+public:
+	b2Vec2 GetAnchorA() const override;
+	b2Vec2 GetAnchorB() const override;
+
+	b2Vec2 GetReactionForce(float32 inv_dt) const override;
+	float32 GetReactionTorque(float32 inv_dt) const override;
+
+	/// The local anchor point relative to bodyA's origin.
+	const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
+
+	/// The local anchor point relative to bodyB's origin.
+	const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
+
+	/// Set the maximum friction force in N.
+	void SetMaxForce(float32 force);
+
+	/// Get the maximum friction force in N.
+	float32 GetMaxForce() const;
+
+	/// Set the maximum friction torque in N*m.
+	void SetMaxTorque(float32 torque);
+
+	/// Get the maximum friction torque in N*m.
+	float32 GetMaxTorque() const;
+
+	/// Dump joint to dmLog
+	void Dump() override;
+
+protected:
+
+	friend class b2Joint;
+
+	b2FrictionJoint(const b2FrictionJointDef* def);
+
+	void InitVelocityConstraints(const b2SolverData& data) override;
+	void SolveVelocityConstraints(const b2SolverData& data) override;
+	bool SolvePositionConstraints(const b2SolverData& data) override;
+
+	b2Vec2 m_localAnchorA;
+	b2Vec2 m_localAnchorB;
+
+	// Solver shared
+	b2Vec2 m_linearImpulse;
+	float32 m_angularImpulse;
+	float32 m_maxForce;
+	float32 m_maxTorque;
+
+	// Solver temp
+	int32 m_indexA;
+	int32 m_indexB;
+	b2Vec2 m_rA;
+	b2Vec2 m_rB;
+	b2Vec2 m_localCenterA;
+	b2Vec2 m_localCenterB;
+	float32 m_invMassA;
+	float32 m_invMassB;
+	float32 m_invIA;
+	float32 m_invIB;
+	b2Mat22 m_linearMass;
+	float32 m_angularMass;
+};
+
+#endif