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.
26struct b2MouseJointDef : public b2JointDef
27{
28 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.
60class b2MouseJoint : public b2Joint
61{
62public:
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.
93 void Dump() { b2Log("Mouse joint dumping is not supported.\n"); }
94
95 /// Implement b2Joint::ShiftOrigin
96 void ShiftOrigin(const b2Vec2& newOrigin);
97
98protected:
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