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