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_JOINT_H
20 #define B2_JOINT_H
21
22 #include <Box2D/Common/b2Math.h>
23
24 class b2Body;
25 class b2Joint;
26 struct b2SolverData;
27 class b2BlockAllocator;
28
29 enum b2JointType
30 {
31 e_unknownJoint,
32 e_revoluteJoint,
33 e_prismaticJoint,
34 e_distanceJoint,
35 e_pulleyJoint,
36 e_mouseJoint,
37 e_gearJoint,
38 e_wheelJoint,
39 e_weldJoint,
40 e_frictionJoint,
41 e_ropeJoint
42 };
43
44 enum b2LimitState
45 {
46 e_inactiveLimit,
47 e_atLowerLimit,
48 e_atUpperLimit,
49 e_equalLimits
50 };
51
52 struct b2Jacobian
53 {
54 b2Vec2 linear;
55 float32 angularA;
56 float32 angularB;
57 };
58
59 /// A joint edge is used to connect bodies and joints together
60 /// in a joint graph where each body is a node and each joint
61 /// is an edge. A joint edge belongs to a doubly linked list
62 /// maintained in each attached body. Each joint has two joint
63 /// nodes, one for each attached body.
64 struct b2JointEdge
65 {
66 b2Body* other; ///< provides quick access to the other body attached.
67 b2Joint* joint; ///< the joint
68 b2JointEdge* prev; ///< the previous joint edge in the body's joint list
69 b2JointEdge* next; ///< the next joint edge in the body's joint list
70 };
71
72 /// Joint definitions are used to construct joints.
73 struct b2JointDef
74 {
b2JointDefb2JointDef75 b2JointDef()
76 {
77 type = e_unknownJoint;
78 userData = NULL;
79 bodyA = NULL;
80 bodyB = NULL;
81 collideConnected = false;
82 }
83
84 /// The joint type is set automatically for concrete joint types.
85 b2JointType type;
86
87 /// Use this to attach application specific data to your joints.
88 void* userData;
89
90 /// The first attached body.
91 b2Body* bodyA;
92
93 /// The second attached body.
94 b2Body* bodyB;
95
96 /// Set this flag to true if the attached bodies should collide.
97 bool collideConnected;
98 };
99
100 /// The base joint class. Joints are used to constraint two bodies together in
101 /// various fashions. Some joints also feature limits and motors.
102 class b2Joint
103 {
104 public:
105
106 /// Get the type of the concrete joint.
107 b2JointType GetType() const;
108
109 /// Get the first body attached to this joint.
110 b2Body* GetBodyA();
111
112 /// Get the second body attached to this joint.
113 b2Body* GetBodyB();
114
115 /// Get the anchor point on bodyA in world coordinates.
116 virtual b2Vec2 GetAnchorA() const = 0;
117
118 /// Get the anchor point on bodyB in world coordinates.
119 virtual b2Vec2 GetAnchorB() const = 0;
120
121 /// Get the reaction force on bodyB at the joint anchor in Newtons.
122 virtual b2Vec2 GetReactionForce(float32 inv_dt) const = 0;
123
124 /// Get the reaction torque on bodyB in N*m.
125 virtual float32 GetReactionTorque(float32 inv_dt) const = 0;
126
127 /// Get the next joint the world joint list.
128 b2Joint* GetNext();
129 const b2Joint* GetNext() const;
130
131 /// Get the user data pointer.
132 void* GetUserData() const;
133
134 /// Set the user data pointer.
135 void SetUserData(void* data);
136
137 /// Short-cut function to determine if either body is inactive.
138 bool IsActive() const;
139
140 /// Get collide connected.
141 /// Note: modifying the collide connect flag won't work correctly because
142 /// the flag is only checked when fixture AABBs begin to overlap.
143 bool GetCollideConnected() const;
144
145 /// Dump this joint to the log file.
Dump()146 virtual void Dump() { b2Log("// Dump is not supported for this joint type.\n"); }
147
148 protected:
149 friend class b2World;
150 friend class b2Body;
151 friend class b2Island;
152 friend class b2GearJoint;
153
154 static b2Joint* Create(const b2JointDef* def, b2BlockAllocator* allocator);
155 static void Destroy(b2Joint* joint, b2BlockAllocator* allocator);
156
157 b2Joint(const b2JointDef* def);
~b2Joint()158 virtual ~b2Joint() {}
159
160 virtual void InitVelocityConstraints(const b2SolverData& data) = 0;
161 virtual void SolveVelocityConstraints(const b2SolverData& data) = 0;
162
163 // This returns true if the position errors are within tolerance.
164 virtual bool SolvePositionConstraints(const b2SolverData& data) = 0;
165
166 b2JointType m_type;
167 b2Joint* m_prev;
168 b2Joint* m_next;
169 b2JointEdge m_edgeA;
170 b2JointEdge m_edgeB;
171 b2Body* m_bodyA;
172 b2Body* m_bodyB;
173
174 int32 m_index;
175
176 bool m_islandFlag;
177 bool m_collideConnected;
178
179 void* m_userData;
180 };
181
GetType()182 inline b2JointType b2Joint::GetType() const
183 {
184 return m_type;
185 }
186
GetBodyA()187 inline b2Body* b2Joint::GetBodyA()
188 {
189 return m_bodyA;
190 }
191
GetBodyB()192 inline b2Body* b2Joint::GetBodyB()
193 {
194 return m_bodyB;
195 }
196
GetNext()197 inline b2Joint* b2Joint::GetNext()
198 {
199 return m_next;
200 }
201
GetNext()202 inline const b2Joint* b2Joint::GetNext() const
203 {
204 return m_next;
205 }
206
GetUserData()207 inline void* b2Joint::GetUserData() const
208 {
209 return m_userData;
210 }
211
SetUserData(void * data)212 inline void b2Joint::SetUserData(void* data)
213 {
214 m_userData = data;
215 }
216
GetCollideConnected()217 inline bool b2Joint::GetCollideConnected() const
218 {
219 return m_collideConnected;
220 }
221
222 #endif
223