/* * Copyright (c) 2006-2011 Erin Catto http://www.box2d.org * * This software is provided 'as-is', without any express or implied * warranty. In no event will the authors be held liable for any damages * arising from the use of this software. * Permission is granted to anyone to use this software for any purpose, * including commercial applications, and to alter it and redistribute it * freely, subject to the following restrictions: * 1. The origin of this software must not be misrepresented; you must not * claim that you wrote the original software. If you use this software * in a product, an acknowledgment in the product documentation would be * appreciated but is not required. * 2. Altered source versions must be plainly marked as such, and must not be * misrepresented as being the original software. * 3. This notice may not be removed or altered from any source distribution. */ #ifndef B2_PRISMATIC_JOINT_H #define B2_PRISMATIC_JOINT_H #include <Box2D/Dynamics/Joints/b2Joint.h> /// Prismatic joint definition. This requires defining a line of /// motion using an axis and an anchor point. The definition uses local /// anchor points and a local axis so that the initial configuration /// can violate the constraint slightly. The joint translation is zero /// when the local anchor points coincide in world space. Using local /// anchors and a local axis helps when saving and loading a game. struct b2PrismaticJointDef : public b2JointDef { b2PrismaticJointDef() { type = e_prismaticJoint; localAnchorA.SetZero(); localAnchorB.SetZero(); localAxisA.Set(1.0f, 0.0f); referenceAngle = 0.0f; enableLimit = false; lowerTranslation = 0.0f; upperTranslation = 0.0f; enableMotor = false; maxMotorForce = 0.0f; motorSpeed = 0.0f; } /// Initialize the bodies, anchors, axis, and reference angle using the world /// anchor and unit world axis. void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor, const b2Vec2& axis); /// The local anchor point relative to bodyA's origin. b2Vec2 localAnchorA; /// The local anchor point relative to bodyB's origin. b2Vec2 localAnchorB; /// The local translation unit axis in bodyA. b2Vec2 localAxisA; /// The constrained angle between the bodies: bodyB_angle - bodyA_angle. float32 referenceAngle; /// Enable/disable the joint limit. bool enableLimit; /// The lower translation limit, usually in meters. float32 lowerTranslation; /// The upper translation limit, usually in meters. float32 upperTranslation; /// Enable/disable the joint motor. bool enableMotor; /// The maximum motor torque, usually in N-m. float32 maxMotorForce; /// The desired motor speed in radians per second. float32 motorSpeed; }; /// A prismatic joint. This joint provides one degree of freedom: translation /// along an axis fixed in bodyA. Relative rotation is prevented. You can /// use a joint limit to restrict the range of motion and a joint motor to /// drive the motion or to model joint friction. class b2PrismaticJoint : public b2Joint { public: b2Vec2 GetAnchorA() const; b2Vec2 GetAnchorB() const; b2Vec2 GetReactionForce(float32 inv_dt) const; float32 GetReactionTorque(float32 inv_dt) const; /// The local anchor point relative to bodyA's origin. const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; } /// The local anchor point relative to bodyB's origin. const b2Vec2& GetLocalAnchorB() const { return m_localAnchorB; } /// The local joint axis relative to bodyA. const b2Vec2& GetLocalAxisA() const { return m_localXAxisA; } /// Get the reference angle. float32 GetReferenceAngle() const { return m_referenceAngle; } /// Get the current joint translation, usually in meters. float32 GetJointTranslation() const; /// Get the current joint translation speed, usually in meters per second. float32 GetJointSpeed() const; /// Is the joint limit enabled? bool IsLimitEnabled() const; /// Enable/disable the joint limit. void EnableLimit(bool flag); /// Get the lower joint limit, usually in meters. float32 GetLowerLimit() const; /// Get the upper joint limit, usually in meters. float32 GetUpperLimit() const; /// Set the joint limits, usually in meters. void SetLimits(float32 lower, float32 upper); /// Is the joint motor enabled? bool IsMotorEnabled() const; /// Enable/disable the joint motor. void EnableMotor(bool flag); /// Set the motor speed, usually in meters per second. void SetMotorSpeed(float32 speed); /// Get the motor speed, usually in meters per second. float32 GetMotorSpeed() const; /// Set the maximum motor force, usually in N. void SetMaxMotorForce(float32 force); float32 GetMaxMotorForce() const { return m_maxMotorForce; } /// Get the current motor force given the inverse time step, usually in N. float32 GetMotorForce(float32 inv_dt) const; /// Dump to b2Log void Dump(); protected: friend class b2Joint; friend class b2GearJoint; b2PrismaticJoint(const b2PrismaticJointDef* def); void InitVelocityConstraints(const b2SolverData& data); void SolveVelocityConstraints(const b2SolverData& data); bool SolvePositionConstraints(const b2SolverData& data); // Solver shared b2Vec2 m_localAnchorA; b2Vec2 m_localAnchorB; b2Vec2 m_localXAxisA; b2Vec2 m_localYAxisA; float32 m_referenceAngle; b2Vec3 m_impulse; float32 m_motorImpulse; float32 m_lowerTranslation; float32 m_upperTranslation; float32 m_maxMotorForce; float32 m_motorSpeed; bool m_enableLimit; bool m_enableMotor; b2LimitState m_limitState; // Solver temp int32 m_indexA; int32 m_indexB; b2Vec2 m_localCenterA; b2Vec2 m_localCenterB; float32 m_invMassA; float32 m_invMassB; float32 m_invIA; float32 m_invIB; b2Vec2 m_axis, m_perp; float32 m_s1, m_s2; float32 m_a1, m_a2; b2Mat33 m_K; float32 m_motorMass; }; inline float32 b2PrismaticJoint::GetMotorSpeed() const { return m_motorSpeed; } #endif