Box2D  2.4.1
A 2D physics engine for games
b2_friction_joint.h
1 // MIT License
2 
3 // Copyright (c) 2019 Erin Catto
4 
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22 
23 #ifndef B2_FRICTION_JOINT_H
24 #define B2_FRICTION_JOINT_H
25 
26 #include "b2_api.h"
27 #include "b2_joint.h"
28 
30 struct B2_API b2FrictionJointDef : public b2JointDef
31 {
33  {
34  type = e_frictionJoint;
35  localAnchorA.SetZero();
36  localAnchorB.SetZero();
37  maxForce = 0.0f;
38  maxTorque = 0.0f;
39  }
40 
43  void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);
44 
47 
50 
52  float maxForce;
53 
55  float maxTorque;
56 };
57 
60 class B2_API b2FrictionJoint : public b2Joint
61 {
62 public:
63  b2Vec2 GetAnchorA() const override;
64  b2Vec2 GetAnchorB() const override;
65 
66  b2Vec2 GetReactionForce(float inv_dt) const override;
67  float GetReactionTorque(float inv_dt) const override;
68 
70  const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
71 
73  const b2Vec2& GetLocalAnchorB() const { return m_localAnchorB; }
74 
76  void SetMaxForce(float force);
77 
79  float GetMaxForce() const;
80 
82  void SetMaxTorque(float torque);
83 
85  float GetMaxTorque() const;
86 
88  void Dump() override;
89 
90 protected:
91 
92  friend class b2Joint;
93 
95 
96  void InitVelocityConstraints(const b2SolverData& data) override;
97  void SolveVelocityConstraints(const b2SolverData& data) override;
98  bool SolvePositionConstraints(const b2SolverData& data) override;
99 
100  b2Vec2 m_localAnchorA;
101  b2Vec2 m_localAnchorB;
102 
103  // Solver shared
104  b2Vec2 m_linearImpulse;
105  float m_angularImpulse;
106  float m_maxForce;
107  float m_maxTorque;
108 
109  // Solver temp
110  int32 m_indexA;
111  int32 m_indexB;
112  b2Vec2 m_rA;
113  b2Vec2 m_rB;
114  b2Vec2 m_localCenterA;
115  b2Vec2 m_localCenterB;
116  float m_invMassA;
117  float m_invMassB;
118  float m_invIA;
119  float m_invIB;
120  b2Mat22 m_linearMass;
121  float m_angularMass;
122 };
123 
124 #endif
A rigid body. These are created via b2World::CreateBody.
Definition: b2_body.h:129
Definition: b2_friction_joint.h:61
float GetReactionTorque(float inv_dt) const override
Get the reaction torque on bodyB in N*m.
const b2Vec2 & GetLocalAnchorA() const
The local anchor point relative to bodyA's origin.
Definition: b2_friction_joint.h:70
const b2Vec2 & GetLocalAnchorB() const
The local anchor point relative to bodyB's origin.
Definition: b2_friction_joint.h:73
float GetMaxTorque() const
Get the maximum friction torque in N*m.
float GetMaxForce() const
Get the maximum friction force in N.
b2Vec2 GetAnchorA() const override
Get the anchor point on bodyA in world coordinates.
void SetMaxTorque(float torque)
Set the maximum friction torque in N*m.
void Dump() override
Dump joint to dmLog.
void SetMaxForce(float force)
Set the maximum friction force in N.
b2Vec2 GetReactionForce(float inv_dt) const override
Get the reaction force on bodyB at the joint anchor in Newtons.
b2Vec2 GetAnchorB() const override
Get the anchor point on bodyB in world coordinates.
Definition: b2_joint.h:111
Friction joint definition.
Definition: b2_friction_joint.h:31
b2Vec2 localAnchorA
The local anchor point relative to bodyA's origin.
Definition: b2_friction_joint.h:46
float maxForce
The maximum friction force in N.
Definition: b2_friction_joint.h:52
float maxTorque
The maximum friction torque in N-m.
Definition: b2_friction_joint.h:55
b2Vec2 localAnchorB
The local anchor point relative to bodyB's origin.
Definition: b2_friction_joint.h:49
void Initialize(b2Body *bodyA, b2Body *bodyB, const b2Vec2 &anchor)
Joint definitions are used to construct joints.
Definition: b2_joint.h:73
A 2-by-2 matrix. Stored in column-major order.
Definition: b2_math.h:172
Solver Data.
Definition: b2_time_step.h:68
A 2D column vector.
Definition: b2_math.h:42