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). 26 struct b2GearJointDef : public b2JointDef 27 { b2GearJointDefb2GearJointDef28 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. 56 class b2GearJoint : public b2Joint 57 { 58 public: 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. GetJoint1()66 b2Joint* GetJoint1() { return m_joint1; } 67 68 /// Get the second joint. GetJoint2()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 78 protected: 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