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# Box2D/Box2D/Dynamics/Joints/b2PrismaticJoint.h

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    00001 /*
    00002 * Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com
    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_PRISMATIC_JOINT_H
    00020 #define B2_PRISMATIC_JOINT_H
    00021
    00022 #include <Box2D/Dynamics/Joints/b2Joint.h>
    00023
    00031 struct b2PrismaticJointDef : public b2JointDef
    00032 {
    00033         b2PrismaticJointDef()
    00034         {
    00035                 type = e_prismaticJoint;
    00036                 localAnchorA.SetZero();
    00037                 localAnchorB.SetZero();
    00038                 localAxis1.Set(1.0f, 0.0f);
    00039                 referenceAngle = 0.0f;
    00040                 enableLimit = false;
    00041                 lowerTranslation = 0.0f;
    00042                 upperTranslation = 0.0f;
    00043                 enableMotor = false;
    00044                 maxMotorForce = 0.0f;
    00045                 motorSpeed = 0.0f;
    00046         }
    00047
    00050         void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor, const b2Vec2& axis);
    00051
    00053         b2Vec2 localAnchorA;
    00054
    00056         b2Vec2 localAnchorB;
    00057
    00059         b2Vec2 localAxis1;
    00060
    00062         float32 referenceAngle;
    00063
    00065         bool enableLimit;
    00066
    00068         float32 lowerTranslation;
    00069
    00071         float32 upperTranslation;
    00072
    00074         bool enableMotor;
    00075
    00077         float32 maxMotorForce;
    00078
    00080         float32 motorSpeed;
    00081 };
    00082
    00087 class b2PrismaticJoint : public b2Joint
    00088 {
    00089 public:
    00090         b2Vec2 GetAnchorA() const;
    00091         b2Vec2 GetAnchorB() const;
    00092
    00093         b2Vec2 GetReactionForce(float32 inv_dt) const;
    00094         float32 GetReactionTorque(float32 inv_dt) const;
    00095
    00097         float32 GetJointTranslation() const;
    00098
    00100         float32 GetJointSpeed() const;
    00101
    00103         bool IsLimitEnabled() const;
    00104
    00106         void EnableLimit(bool flag);
    00107
    00109         float32 GetLowerLimit() const;
    00110
    00112         float32 GetUpperLimit() const;
    00113
    00115         void SetLimits(float32 lower, float32 upper);
    00116
    00118         bool IsMotorEnabled() const;
    00119
    00121         void EnableMotor(bool flag);
    00122
    00124         void SetMotorSpeed(float32 speed);
    00125
    00127         float32 GetMotorSpeed() const;
    00128
    00130         void SetMaxMotorForce(float32 force);
    00131
    00133         float32 GetMotorForce() const;
    00134
    00135 protected:
    00136         friend class b2Joint;
    00137         friend class b2GearJoint;
    00138         b2PrismaticJoint(const b2PrismaticJointDef* def);
    00139
    00140         void InitVelocityConstraints(const b2TimeStep& step);
    00141         void SolveVelocityConstraints(const b2TimeStep& step);
    00142         bool SolvePositionConstraints(float32 baumgarte);
    00143
    00144         b2Vec2 m_localAnchor1;
    00145         b2Vec2 m_localAnchor2;
    00146         b2Vec2 m_localXAxis1;
    00147         b2Vec2 m_localYAxis1;
    00148         float32 m_refAngle;
    00149
    00150         b2Vec2 m_axis, m_perp;
    00151         float32 m_s1, m_s2;
    00152         float32 m_a1, m_a2;
    00153
    00154         b2Mat33 m_K;
    00155         b2Vec3 m_impulse;
    00156
    00157         float32 m_motorMass;                    // effective mass for motor/limit translational constraint.
    00158         float32 m_motorImpulse;
    00159
    00160         float32 m_lowerTranslation;
    00161         float32 m_upperTranslation;
    00162         float32 m_maxMotorForce;
    00163         float32 m_motorSpeed;
    00164
    00165         bool m_enableLimit;
    00166         bool m_enableMotor;
    00167         b2LimitState m_limitState;
    00168 };
    00169
    00170 inline float32 b2PrismaticJoint::GetMotorSpeed() const
    00171 {
    00172         return m_motorSpeed;
    00173 }
    00174
    00175 #endif