File indexing completed on 2024-12-29 03:29:27

 /*
 * 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