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_MOUSE_JOINT_H 20 #define B2_MOUSE_JOINT_H 21 22 #include "Box2D/Dynamics/Joints/b2Joint.h" 23 24 /// Mouse joint definition. This requires a world target point, 25 /// tuning parameters, and the time step. 26 struct b2MouseJointDef : public b2JointDef 27 { b2MouseJointDefb2MouseJointDef28 b2MouseJointDef() 29 { 30 type = e_mouseJoint; 31 target.Set(0.0f, 0.0f); 32 maxForce = 0.0f; 33 frequencyHz = 5.0f; 34 dampingRatio = 0.7f; 35 } 36 37 /// The initial world target point. This is assumed 38 /// to coincide with the body anchor initially. 39 b2Vec2 target; 40 41 /// The maximum constraint force that can be exerted 42 /// to move the candidate body. Usually you will express 43 /// as some multiple of the weight (multiplier * mass * gravity). 44 float32 maxForce; 45 46 /// The response speed. 47 float32 frequencyHz; 48 49 /// The damping ratio. 0 = no damping, 1 = critical damping. 50 float32 dampingRatio; 51 }; 52 53 /// A mouse joint is used to make a point on a body track a 54 /// specified world point. This a soft constraint with a maximum 55 /// force. This allows the constraint to stretch and without 56 /// applying huge forces. 57 /// NOTE: this joint is not documented in the manual because it was 58 /// developed to be used in the testbed. If you want to learn how to 59 /// use the mouse joint, look at the testbed. 60 class b2MouseJoint : public b2Joint 61 { 62 public: 63 64 /// Implements b2Joint. 65 b2Vec2 GetAnchorA() const; 66 67 /// Implements b2Joint. 68 b2Vec2 GetAnchorB() const; 69 70 /// Implements b2Joint. 71 b2Vec2 GetReactionForce(float32 inv_dt) const; 72 73 /// Implements b2Joint. 74 float32 GetReactionTorque(float32 inv_dt) const; 75 76 /// Use this to update the target point. 77 void SetTarget(const b2Vec2& target); 78 const b2Vec2& GetTarget() const; 79 80 /// Set/get the maximum force in Newtons. 81 void SetMaxForce(float32 force); 82 float32 GetMaxForce() const; 83 84 /// Set/get the frequency in Hertz. 85 void SetFrequency(float32 hz); 86 float32 GetFrequency() const; 87 88 /// Set/get the damping ratio (dimensionless). 89 void SetDampingRatio(float32 ratio); 90 float32 GetDampingRatio() const; 91 92 /// The mouse joint does not support dumping. Dump()93 void Dump() { b2Log("Mouse joint dumping is not supported.\n"); } 94 95 /// Implement b2Joint::ShiftOrigin 96 void ShiftOrigin(const b2Vec2& newOrigin); 97 98 protected: 99 friend class b2Joint; 100 101 b2MouseJoint(const b2MouseJointDef* def); 102 103 void InitVelocityConstraints(const b2SolverData& data); 104 void SolveVelocityConstraints(const b2SolverData& data); 105 bool SolvePositionConstraints(const b2SolverData& data); 106 107 b2Vec2 m_localAnchorB; 108 b2Vec2 m_targetA; 109 float32 m_frequencyHz; 110 float32 m_dampingRatio; 111 float32 m_beta; 112 113 // Solver shared 114 b2Vec2 m_impulse; 115 float32 m_maxForce; 116 float32 m_gamma; 117 118 // Solver temp 119 int32 m_indexA; 120 int32 m_indexB; 121 b2Vec2 m_rB; 122 b2Vec2 m_localCenterB; 123 float32 m_invMassB; 124 float32 m_invIB; 125 b2Mat22 m_mass; 126 b2Vec2 m_C; 127 }; 128 129 #endif 130