1/*
2* Copyright (c) 2006-2011 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_GEAR_JOINT_H
20#define B2_GEAR_JOINT_H
21
22#include <Box2D/Dynamics/Joints/b2Joint.h>
23
24/// Gear joint definition. This definition requires two existing
25/// revolute or prismatic joints (any combination will work).
26struct b2GearJointDef : public b2JointDef
27{
28 b2GearJointDef()
29 {
30 type = e_gearJoint;
31 joint1 = NULL;
32 joint2 = NULL;
33 ratio = 1.0f;
34 }
35
36 /// The first revolute/prismatic joint attached to the gear joint.
37 b2Joint* joint1;
38
39 /// The second revolute/prismatic joint attached to the gear joint.
40 b2Joint* joint2;
41
42 /// The gear ratio.
43 /// @see b2GearJoint for explanation.
44 float32 ratio;
45};
46
47/// A gear joint is used to connect two joints together. Either joint
48/// can be a revolute or prismatic joint. You specify a gear ratio
49/// to bind the motions together:
50/// coordinate1 + ratio * coordinate2 = constant
51/// The ratio can be negative or positive. If one joint is a revolute joint
52/// and the other joint is a prismatic joint, then the ratio will have units
53/// of length or units of 1/length.
54/// @warning You have to manually destroy the gear joint if joint1 or joint2
55/// is destroyed.
56class b2GearJoint : public b2Joint
57{
58public:
59 b2Vec2 GetAnchorA() const;
60 b2Vec2 GetAnchorB() const;
61
62 b2Vec2 GetReactionForce(float32 inv_dt) const;
63 float32 GetReactionTorque(float32 inv_dt) const;
64
65 /// Get the first joint.
66 b2Joint* GetJoint1() { return m_joint1; }
67
68 /// Get the second joint.
69 b2Joint* GetJoint2() { return m_joint2; }
70
71 /// Set/Get the gear ratio.
72 void SetRatio(float32 ratio);
73 float32 GetRatio() const;
74
75 /// Dump joint to dmLog
76 void Dump();
77
78protected:
79
80 friend class b2Joint;
81 b2GearJoint(const b2GearJointDef* data);
82
83 void InitVelocityConstraints(const b2SolverData& data);
84 void SolveVelocityConstraints(const b2SolverData& data);
85 bool SolvePositionConstraints(const b2SolverData& data);
86
87 b2Joint* m_joint1;
88 b2Joint* m_joint2;
89
90 b2JointType m_typeA;
91 b2JointType m_typeB;
92
93 // Body A is connected to body C
94 // Body B is connected to body D
95 b2Body* m_bodyC;
96 b2Body* m_bodyD;
97
98 // Solver shared
99 b2Vec2 m_localAnchorA;
100 b2Vec2 m_localAnchorB;
101 b2Vec2 m_localAnchorC;
102 b2Vec2 m_localAnchorD;
103
104 b2Vec2 m_localAxisC;
105 b2Vec2 m_localAxisD;
106
107 float32 m_referenceAngleA;
108 float32 m_referenceAngleB;
109
110 float32 m_constant;
111 float32 m_ratio;
112
113 float32 m_impulse;
114
115 // Solver temp
116 int32 m_indexA, m_indexB, m_indexC, m_indexD;
117 b2Vec2 m_lcA, m_lcB, m_lcC, m_lcD;
118 float32 m_mA, m_mB, m_mC, m_mD;
119 float32 m_iA, m_iB, m_iC, m_iD;
120 b2Vec2 m_JvAC, m_JvBD;
121 float32 m_JwA, m_JwB, m_JwC, m_JwD;
122 float32 m_mass;
123};
124
125#endif
126