1 /*
2 * Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com
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 JOINT_H
20 #define JOINT_H
21
22 #include "../../Common/b2Math.h"
23
24 class b2Body;
25 class b2Joint;
26 struct b2TimeStep;
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 };
39
40 enum b2LimitState
41 {
42 e_inactiveLimit,
43 e_atLowerLimit,
44 e_atUpperLimit,
45 e_equalLimits
46 };
47
48 struct b2Jacobian
49 {
50 b2Vec2 linear1;
51 float32 angular1;
52 b2Vec2 linear2;
53 float32 angular2;
54
55 void SetZero();
56 void Set(const b2Vec2& x1, float32 a1, const b2Vec2& x2, float32 a2);
57 float32 Compute(const b2Vec2& x1, float32 a1, const b2Vec2& x2, float32 a2);
58 };
59
60 /// A joint edge is used to connect bodies and joints together
61 /// in a joint graph where each body is a node and each joint
62 /// is an edge. A joint edge belongs to a doubly linked list
63 /// maintained in each attached body. Each joint has two joint
64 /// nodes, one for each attached body.
65 struct b2JointEdge
66 {
67 b2Body* other; ///< provides quick access to the other body attached.
68 b2Joint* joint; ///< the joint
69 b2JointEdge* prev; ///< the previous joint edge in the body's joint list
70 b2JointEdge* next; ///< the next joint edge in the body's joint list
71 };
72
73 /// Joint definitions are used to construct joints.
74 struct b2JointDef
75 {
b2JointDefb2JointDef76 b2JointDef()
77 {
78 type = e_unknownJoint;
79 userData = NULL;
80 body1 = NULL;
81 body2 = NULL;
82 collideConnected = false;
83 }
84
85 /// The joint type is set automatically for concrete joint types.
86 b2JointType type;
87
88 /// Use this to attach application specific data to your joints.
89 void* userData;
90
91 /// The first attached body.
92 b2Body* body1;
93
94 /// The second attached body.
95 b2Body* body2;
96
97 /// Set this flag to true if the attached bodies should collide.
98 bool collideConnected;
99 };
100
101 /// The base joint class. Joints are used to constraint two bodies together in
102 /// various fashions. Some joints also feature limits and motors.
103 class b2Joint
104 {
105 public:
106
107 /// Get the type of the concrete joint.
108 b2JointType GetType() const;
109
110 /// Get the first body attached to this joint.
111 b2Body* GetBody1();
112
113 /// Get the second body attached to this joint.
114 b2Body* GetBody2();
115
116 /// Get the anchor point on body1 in world coordinates.
117 virtual b2Vec2 GetAnchor1() const = 0;
118
119 /// Get the anchor point on body2 in world coordinates.
120 virtual b2Vec2 GetAnchor2() const = 0;
121
122 /// Get the reaction force on body2 at the joint anchor.
123 virtual b2Vec2 GetReactionForce() const = 0;
124
125 /// Get the reaction torque on body2.
126 virtual float32 GetReactionTorque() const = 0;
127
128 /// Get the next joint the world joint list.
129 b2Joint* GetNext();
130
131 /// Get the user data pointer.
132 void* GetUserData();
133
134 /// Set the user data pointer.
135 void SetUserData(void* data);
136
137 //--------------- Internals Below -------------------
138 protected:
139 friend class b2World;
140 friend class b2Body;
141 friend class b2Island;
142
143 static b2Joint* Create(const b2JointDef* def, b2BlockAllocator* allocator);
144 static void Destroy(b2Joint* joint, b2BlockAllocator* allocator);
145
146 b2Joint(const b2JointDef* def);
~b2Joint()147 virtual ~b2Joint() {}
148
149 virtual void InitVelocityConstraints(const b2TimeStep& step) = 0;
150 virtual void SolveVelocityConstraints(const b2TimeStep& step) = 0;
151
152 // This returns true if the position errors are within tolerance.
InitPositionConstraints()153 virtual void InitPositionConstraints() {}
154 virtual bool SolvePositionConstraints() = 0;
155
156 b2JointType m_type;
157 b2Joint* m_prev;
158 b2Joint* m_next;
159 b2JointEdge m_node1;
160 b2JointEdge m_node2;
161 b2Body* m_body1;
162 b2Body* m_body2;
163
164 float32 m_inv_dt;
165
166 bool m_islandFlag;
167 bool m_collideConnected;
168
169 void* m_userData;
170 };
171
SetZero()172 inline void b2Jacobian::SetZero()
173 {
174 linear1.SetZero(); angular1 = 0.0f;
175 linear2.SetZero(); angular2 = 0.0f;
176 }
177
Set(const b2Vec2 & x1,float32 a1,const b2Vec2 & x2,float32 a2)178 inline void b2Jacobian::Set(const b2Vec2& x1, float32 a1, const b2Vec2& x2, float32 a2)
179 {
180 linear1 = x1; angular1 = a1;
181 linear2 = x2; angular2 = a2;
182 }
183
Compute(const b2Vec2 & x1,float32 a1,const b2Vec2 & x2,float32 a2)184 inline float32 b2Jacobian::Compute(const b2Vec2& x1, float32 a1, const b2Vec2& x2, float32 a2)
185 {
186 return b2Dot(linear1, x1) + angular1 * a1 + b2Dot(linear2, x2) + angular2 * a2;
187 }
188
GetType()189 inline b2JointType b2Joint::GetType() const
190 {
191 return m_type;
192 }
193
GetBody1()194 inline b2Body* b2Joint::GetBody1()
195 {
196 return m_body1;
197 }
198
GetBody2()199 inline b2Body* b2Joint::GetBody2()
200 {
201 return m_body2;
202 }
203
GetNext()204 inline b2Joint* b2Joint::GetNext()
205 {
206 return m_next;
207 }
208
GetUserData()209 inline void* b2Joint::GetUserData()
210 {
211 return m_userData;
212 }
213
SetUserData(void * data)214 inline void b2Joint::SetUserData(void* data)
215 {
216 m_userData = data;
217 }
218
219 #endif
220