1/*
2* Copyright (c) 2006-2012 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_MOTOR_JOINT_H
20#define B2_MOTOR_JOINT_H
21
22#include <Box2D/Dynamics/Joints/b2Joint.h>
23
24/// Motor joint definition.
25struct b2MotorJointDef : public b2JointDef
26{
27 b2MotorJointDef()
28 {
29 type = e_motorJoint;
30 linearOffset.SetZero();
31 angularOffset = 0.0f;
32 maxForce = 1.0f;
33 maxTorque = 1.0f;
34 correctionFactor = 0.3f;
35 }
36
37 /// Initialize the bodies and offsets using the current transforms.
38 void Initialize(b2Body* bodyA, b2Body* bodyB);
39
40 /// Position of bodyB minus the position of bodyA, in bodyA's frame, in meters.
41 b2Vec2 linearOffset;
42
43 /// The bodyB angle minus bodyA angle in radians.
44 float32 angularOffset;
45
46 /// The maximum motor force in N.
47 float32 maxForce;
48
49 /// The maximum motor torque in N-m.
50 float32 maxTorque;
51
52 /// Position correction factor in the range [0,1].
53 float32 correctionFactor;
54};
55
56/// A motor joint is used to control the relative motion
57/// between two bodies. A typical usage is to control the movement
58/// of a dynamic body with respect to the ground.
59class b2MotorJoint : public b2Joint
60{
61public:
62 b2Vec2 GetAnchorA() const;
63 b2Vec2 GetAnchorB() const;
64
65 b2Vec2 GetReactionForce(float32 inv_dt) const;
66 float32 GetReactionTorque(float32 inv_dt) const;
67
68 /// Set/get the target linear offset, in frame A, in meters.
69 void SetLinearOffset(const b2Vec2& linearOffset);
70 const b2Vec2& GetLinearOffset() const;
71
72 /// Set/get the target angular offset, in radians.
73 void SetAngularOffset(float32 angularOffset);
74 float32 GetAngularOffset() const;
75
76 /// Set the maximum friction force in N.
77 void SetMaxForce(float32 force);
78
79 /// Get the maximum friction force in N.
80 float32 GetMaxForce() const;
81
82 /// Set the maximum friction torque in N*m.
83 void SetMaxTorque(float32 torque);
84
85 /// Get the maximum friction torque in N*m.
86 float32 GetMaxTorque() const;
87
88 /// Set the position correction factor in the range [0,1].
89 void SetCorrectionFactor(float32 factor);
90
91 /// Get the position correction factor in the range [0,1].
92 float32 GetCorrectionFactor() const;
93
94 /// Dump to b2Log
95 void Dump();
96
97protected:
98
99 friend class b2Joint;
100
101 b2MotorJoint(const b2MotorJointDef* def);
102
103 void InitVelocityConstraints(const b2SolverData& data);
104 void SolveVelocityConstraints(const b2SolverData& data);
105 bool SolvePositionConstraints(const b2SolverData& data);
106
107 // Solver shared
108 b2Vec2 m_linearOffset;
109 float32 m_angularOffset;
110 b2Vec2 m_linearImpulse;
111 float32 m_angularImpulse;
112 float32 m_maxForce;
113 float32 m_maxTorque;
114 float32 m_correctionFactor;
115
116 // Solver temp
117 int32 m_indexA;
118 int32 m_indexB;
119 b2Vec2 m_rA;
120 b2Vec2 m_rB;
121 b2Vec2 m_localCenterA;
122 b2Vec2 m_localCenterB;
123 b2Vec2 m_linearError;
124 float32 m_angularError;
125 float32 m_invMassA;
126 float32 m_invMassB;
127 float32 m_invIA;
128 float32 m_invIB;
129 b2Mat22 m_linearMass;
130 float32 m_angularMass;
131};
132
133#endif
134