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b2WheelJoint.h

    00001 /*
    00002 * Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
    00003 *
    00004 * This software is provided 'as-is', without any express or implied
    00005 * warranty.  In no event will the authors be held liable for any damages
    00006 * arising from the use of this software.
    00007 * Permission is granted to anyone to use this software for any purpose,
    00008 * including commercial applications, and to alter it and redistribute it
    00009 * freely, subject to the following restrictions:
    00010 * 1. The origin of this software must not be misrepresented; you must not
    00011 * claim that you wrote the original software. If you use this software
    00012 * in a product, an acknowledgment in the product documentation would be
    00013 * appreciated but is not required.
    00014 * 2. Altered source versions must be plainly marked as such, and must not be
    00015 * misrepresented as being the original software.
    00016 * 3. This notice may not be removed or altered from any source distribution.
    00017 */
    00018
    00019 #ifndef B2_WHEEL_JOINT_H
    00020 #define B2_WHEEL_JOINT_H
    00021
    00022 #include <Box2D/Dynamics/Joints/b2Joint.h>
    00023
    00030 struct b2WheelJointDef : public b2JointDef
    00031 {
    00032         b2WheelJointDef()
    00033         {
    00034                 type = e_wheelJoint;
    00035                 localAnchorA.SetZero();
    00036                 localAnchorB.SetZero();
    00037                 localAxisA.Set(1.0f, 0.0f);
    00038                 enableMotor = false;
    00039                 maxMotorTorque = 0.0f;
    00040                 motorSpeed = 0.0f;
    00041                 frequencyHz = 2.0f;
    00042                 dampingRatio = 0.7f;
    00043         }
    00044
    00047         void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor, const b2Vec2& axis);
    00048
    00050         b2Vec2 localAnchorA;
    00051
    00053         b2Vec2 localAnchorB;
    00054
    00056         b2Vec2 localAxisA;
    00057
    00059         bool enableMotor;
    00060
    00062         float32 maxMotorTorque;
    00063
    00065         float32 motorSpeed;
    00066
    00068         float32 frequencyHz;
    00069
    00071         float32 dampingRatio;
    00072 };
    00073
    00079 class b2WheelJoint : public b2Joint
    00080 {
    00081 public:
    00082         void GetDefinition(b2WheelJointDef* def) const;
    00083
    00084         b2Vec2 GetAnchorA() const;
    00085         b2Vec2 GetAnchorB() const;
    00086
    00087         b2Vec2 GetReactionForce(float32 inv_dt) const;
    00088         float32 GetReactionTorque(float32 inv_dt) const;
    00089
    00091         const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
    00092
    00094         const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
    00095
    00097         const b2Vec2& GetLocalAxisA() const { return m_localXAxisA; }
    00098
    00100         float32 GetJointTranslation() const;
    00101
    00103         float32 GetJointSpeed() const;
    00104
    00106         bool IsMotorEnabled() const;
    00107
    00109         void EnableMotor(bool flag);
    00110
    00112         void SetMotorSpeed(float32 speed);
    00113
    00115         float32 GetMotorSpeed() const;
    00116
    00118         void SetMaxMotorTorque(float32 torque);
    00119         float32 GetMaxMotorTorque() const;
    00120
    00122         float32 GetMotorTorque(float32 inv_dt) const;
    00123
    00125         void SetSpringFrequencyHz(float32 hz);
    00126         float32 GetSpringFrequencyHz() const;
    00127
    00129         void SetSpringDampingRatio(float32 ratio);
    00130         float32 GetSpringDampingRatio() const;
    00131
    00133         void Dump();
    00134
    00135 protected:
    00136
    00137         friend class b2Joint;
    00138         b2WheelJoint(const b2WheelJointDef* def);
    00139
    00140         void InitVelocityConstraints(const b2SolverData& data);
    00141         void SolveVelocityConstraints(const b2SolverData& data);
    00142         bool SolvePositionConstraints(const b2SolverData& data);
    00143
    00144         float32 m_frequencyHz;
    00145         float32 m_dampingRatio;
    00146
    00147         // Solver shared
    00148         b2Vec2 m_localAnchorA;
    00149         b2Vec2 m_localAnchorB;
    00150         b2Vec2 m_localXAxisA;
    00151         b2Vec2 m_localYAxisA;
    00152
    00153         float32 m_impulse;
    00154         float32 m_motorImpulse;
    00155         float32 m_springImpulse;
    00156
    00157         float32 m_maxMotorTorque;
    00158         float32 m_motorSpeed;
    00159         bool m_enableMotor;
    00160
    00161         // Solver temp
    00162         int32 m_indexA;
    00163         int32 m_indexB;
    00164         b2Vec2 m_localCenterA;
    00165         b2Vec2 m_localCenterB;
    00166         float32 m_invMassA;
    00167         float32 m_invMassB;
    00168         float32 m_invIA;
    00169         float32 m_invIB;
    00170
    00171         b2Vec2 m_ax, m_ay;
    00172         float32 m_sAx, m_sBx;
    00173         float32 m_sAy, m_sBy;
    00174
    00175         float32 m_mass;
    00176         float32 m_motorMass;
    00177         float32 m_springMass;
    00178
    00179         float32 m_bias;
    00180         float32 m_gamma;
    00181 };
    00182
    00183 inline float32 b2WheelJoint::GetMotorSpeed() const
    00184 {
    00185         return m_motorSpeed;
    00186 }
    00187
    00188 inline float32 b2WheelJoint::GetMaxMotorTorque() const
    00189 {
    00190         return m_maxMotorTorque;
    00191 }
    00192
    00193 inline void b2WheelJoint::SetSpringFrequencyHz(float32 hz)
    00194 {
    00195         m_frequencyHz = hz;
    00196 }
    00197
    00198 inline float32 b2WheelJoint::GetSpringFrequencyHz() const
    00199 {
    00200         return m_frequencyHz;
    00201 }
    00202
    00203 inline void b2WheelJoint::SetSpringDampingRatio(float32 ratio)
    00204 {
    00205         m_dampingRatio = ratio;
    00206 }
    00207
    00208 inline float32 b2WheelJoint::GetSpringDampingRatio() const
    00209 {
    00210         return m_dampingRatio;
    00211 }
    00212
    00213 #endif

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