1/*
2* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
3*
4* This software is provided 'as-is', without any express or implied
5* warranty.  In no event will the authors be held liable for any damages
6* arising from the use of this software.
7* Permission is granted to anyone to use this software for any purpose,
8* including commercial applications, and to alter it and redistribute it
9* freely, subject to the following restrictions:
10* 1. The origin of this software must not be misrepresented; you must not
11* claim that you wrote the original software. If you use this software
12* in a product, an acknowledgment in the product documentation would be
13* appreciated but is not required.
14* 2. Altered source versions must be plainly marked as such, and must not be
15* misrepresented as being the original software.
16* 3. This notice may not be removed or altered from any source distribution.
17*/
18
19#ifndef B2_FRICTION_JOINT_H
20#define B2_FRICTION_JOINT_H
21
22#include <Box2D/Dynamics/Joints/b2Joint.h>
23
24/// Friction joint definition.
25struct b2FrictionJointDef : public b2JointDef
26{
27	b2FrictionJointDef()
28	{
29		type = e_frictionJoint;
30		localAnchorA.SetZero();
31		localAnchorB.SetZero();
32		maxForce = 0.0f;
33		maxTorque = 0.0f;
34	}
35
36	/// Initialize the bodies, anchors, axis, and reference angle using the world
37	/// anchor and world axis.
38	void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);
39
40	/// The local anchor point relative to bodyA's origin.
41	b2Vec2 localAnchorA;
42
43	/// The local anchor point relative to bodyB's origin.
44	b2Vec2 localAnchorB;
45
46	/// The maximum friction force in N.
47	float32 maxForce;
48
49	/// The maximum friction torque in N-m.
50	float32 maxTorque;
51};
52
53/// Friction joint. This is used for top-down friction.
54/// It provides 2D translational friction and angular friction.
55class b2FrictionJoint : public b2Joint
56{
57public:
58	b2Vec2 GetAnchorA() const;
59	b2Vec2 GetAnchorB() const;
60
61	b2Vec2 GetReactionForce(float32 inv_dt) const;
62	float32 GetReactionTorque(float32 inv_dt) const;
63
64	/// The local anchor point relative to bodyA's origin.
65	const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
66
67	/// The local anchor point relative to bodyB's origin.
68	const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
69
70	/// Set the maximum friction force in N.
71	void SetMaxForce(float32 force);
72
73	/// Get the maximum friction force in N.
74	float32 GetMaxForce() const;
75
76	/// Set the maximum friction torque in N*m.
77	void SetMaxTorque(float32 torque);
78
79	/// Get the maximum friction torque in N*m.
80	float32 GetMaxTorque() const;
81
82	/// Dump joint to dmLog
83	void Dump();
84
85protected:
86
87	friend class b2Joint;
88
89	b2FrictionJoint(const b2FrictionJointDef* def);
90
91	void InitVelocityConstraints(const b2SolverData& data);
92	void SolveVelocityConstraints(const b2SolverData& data);
93	bool SolvePositionConstraints(const b2SolverData& data);
94
95	b2Vec2 m_localAnchorA;
96	b2Vec2 m_localAnchorB;
97
98	// Solver shared
99	b2Vec2 m_linearImpulse;
100	float32 m_angularImpulse;
101	float32 m_maxForce;
102	float32 m_maxTorque;
103
104	// Solver temp
105	int32 m_indexA;
106	int32 m_indexB;
107	b2Vec2 m_rA;
108	b2Vec2 m_rB;
109	b2Vec2 m_localCenterA;
110	b2Vec2 m_localCenterB;
111	float32 m_invMassA;
112	float32 m_invMassB;
113	float32 m_invIA;
114	float32 m_invIB;
115	b2Mat22 m_linearMass;
116	float32 m_angularMass;
117};
118
119#endif
120