Box2D  2.3.0
A 2D Physics Engine for Games
b2FrictionJoint.h
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 
25 struct 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 
38  void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);
39 
41  b2Vec2 localAnchorA;
42 
44  b2Vec2 localAnchorB;
45 
47  float32 maxForce;
48 
50  float32 maxTorque;
51 };
52 
55 class b2FrictionJoint : public b2Joint
56 {
57 public:
58  b2Vec2 GetAnchorA() const;
59  b2Vec2 GetAnchorB() const;
60 
61  b2Vec2 GetReactionForce(float32 inv_dt) const;
62  float32 GetReactionTorque(float32 inv_dt) const;
63 
65  const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
66 
68  const b2Vec2& GetLocalAnchorB() const { return m_localAnchorB; }
69 
71  void SetMaxForce(float32 force);
72 
74  float32 GetMaxForce() const;
75 
77  void SetMaxTorque(float32 torque);
78 
80  float32 GetMaxTorque() const;
81 
83  void Dump();
84 
85 protected:
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
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