Box2D  2.4.0
A 2D physics engine for games
b2_distance_joint.h
1 // MIT License
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3 // Copyright (c) 2019 Erin Catto
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22 
23 #ifndef B2_DISTANCE_JOINT_H
24 #define B2_DISTANCE_JOINT_H
25 
26 #include "b2_api.h"
27 #include "b2_joint.h"
28 
34 struct B2_API b2DistanceJointDef : public b2JointDef
35 {
37  {
38  type = e_distanceJoint;
39  localAnchorA.Set(0.0f, 0.0f);
40  localAnchorB.Set(0.0f, 0.0f);
41  length = 1.0f;
42  stiffness = 0.0f;
43  damping = 0.0f;
44  }
45 
48  void Initialize(b2Body* bodyA, b2Body* bodyB,
49  const b2Vec2& anchorA, const b2Vec2& anchorB);
50 
53 
56 
58  float length;
59 
61  float stiffness;
62 
64  float damping;
65 };
66 
69 class B2_API b2DistanceJoint : public b2Joint
70 {
71 public:
72 
73  b2Vec2 GetAnchorA() const override;
74  b2Vec2 GetAnchorB() const override;
75 
78  b2Vec2 GetReactionForce(float inv_dt) const override;
79 
82  float GetReactionTorque(float inv_dt) const override;
83 
85  const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
86 
88  const b2Vec2& GetLocalAnchorB() const { return m_localAnchorB; }
89 
92  void SetLength(float length) { m_length = length; }
93  float GetLength() const { return m_length; }
94 
96  void SetStiffness(float stiffness) { m_stiffness = stiffness; }
97  float GetStiffness() const { return m_stiffness; }
98 
100  void SetDamping(float damping) { m_damping = damping; }
101  float GetDamping() const { return m_damping; }
102 
104  void Dump() override;
105 
106 protected:
107 
108  friend class b2Joint;
109  b2DistanceJoint(const b2DistanceJointDef* data);
110 
111  void InitVelocityConstraints(const b2SolverData& data) override;
112  void SolveVelocityConstraints(const b2SolverData& data) override;
113  bool SolvePositionConstraints(const b2SolverData& data) override;
114 
115  float m_stiffness;
116  float m_damping;
117  float m_bias;
118 
119  // Solver shared
120  b2Vec2 m_localAnchorA;
121  b2Vec2 m_localAnchorB;
122  float m_gamma;
123  float m_impulse;
124  float m_length;
125 
126  // Solver temp
127  int32 m_indexA;
128  int32 m_indexB;
129  b2Vec2 m_u;
130  b2Vec2 m_rA;
131  b2Vec2 m_rB;
132  b2Vec2 m_localCenterA;
133  b2Vec2 m_localCenterB;
134  float m_invMassA;
135  float m_invMassB;
136  float m_invIA;
137  float m_invIB;
138  float m_mass;
139 };
140 
141 #endif
b2Vec2
A 2D column vector.
Definition: b2_math.h:42
b2Body
A rigid body. These are created via b2World::CreateBody.
Definition: b2_body.h:133
b2DistanceJoint::GetAnchorB
b2Vec2 GetAnchorB() const override
Get the anchor point on bodyB in world coordinates.
b2DistanceJoint
Definition: b2_distance_joint.h:70
b2DistanceJoint::GetLocalAnchorA
const b2Vec2 & GetLocalAnchorA() const
The local anchor point relative to bodyA's origin.
Definition: b2_distance_joint.h:85
b2DistanceJoint::SetDamping
void SetDamping(float damping)
Set/get linear damping in N*s/m.
Definition: b2_distance_joint.h:100
b2JointDef
Joint definitions are used to construct joints.
Definition: b2_joint.h:73
b2DistanceJoint::GetLocalAnchorB
const b2Vec2 & GetLocalAnchorB() const
The local anchor point relative to bodyB's origin.
Definition: b2_distance_joint.h:88
b2DistanceJointDef::localAnchorA
b2Vec2 localAnchorA
The local anchor point relative to bodyA's origin.
Definition: b2_distance_joint.h:52
b2DistanceJointDef::damping
float damping
The linear damping in N*s/m.
Definition: b2_distance_joint.h:64
b2DistanceJoint::Dump
void Dump() override
Dump joint to dmLog.
b2DistanceJointDef::length
float length
The natural length between the anchor points.
Definition: b2_distance_joint.h:58
b2DistanceJointDef::stiffness
float stiffness
The linear stiffness in N/m. A value of 0 disables softness.
Definition: b2_distance_joint.h:61
b2DistanceJoint::SetLength
void SetLength(float length)
Definition: b2_distance_joint.h:92
b2DistanceJoint::GetReactionTorque
float GetReactionTorque(float inv_dt) const override
b2DistanceJoint::GetAnchorA
b2Vec2 GetAnchorA() const override
Get the anchor point on bodyA in world coordinates.
b2SolverData
Solver Data.
Definition: b2_time_step.h:68
b2DistanceJoint::GetReactionForce
b2Vec2 GetReactionForce(float inv_dt) const override
b2DistanceJointDef::localAnchorB
b2Vec2 localAnchorB
The local anchor point relative to bodyB's origin.
Definition: b2_distance_joint.h:55
b2DistanceJoint::SetStiffness
void SetStiffness(float stiffness)
Set/get the linear stiffness in N/m.
Definition: b2_distance_joint.h:96
b2Joint
Definition: b2_joint.h:112
b2DistanceJointDef
Definition: b2_distance_joint.h:35
b2DistanceJointDef::Initialize
void Initialize(b2Body *bodyA, b2Body *bodyB, const b2Vec2 &anchorA, const b2Vec2 &anchorB)