b2Joint.h

/*
* Copyright (c) 2006-2007 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_JOINT_H
#define B2_JOINT_H

#include <Box2D/Common/b2Math.h>

class b2Body;
class b2Joint;
struct b2SolverData;
class b2BlockAllocator;

enum b2JointType
{
    e_unknownJoint,
    e_revoluteJoint,
    e_prismaticJoint,
    e_distanceJoint,
    e_pulleyJoint,
    e_mouseJoint,
    e_gearJoint,
    e_wheelJoint,
    e_weldJoint,
    e_frictionJoint,
    e_ropeJoint,
    e_motorJoint
};

enum b2LimitState
{
    e_inactiveLimit,
    e_atLowerLimit,
    e_atUpperLimit,
    e_equalLimits
};

struct b2Jacobian
{
    b2Vec2 linear;
    float32 angularA;
    float32 angularB;
};

struct b2JointEdge
{
    b2Body* other;          
    b2Joint* joint;         
    b2JointEdge* prev;      
    b2JointEdge* next;      
};

struct b2JointDef
{
    b2JointDef()
    {
        type = e_unknownJoint;
        userData = NULL;
        bodyA = NULL;
        bodyB = NULL;
        collideConnected = false;
    }

    b2JointType type;

    void* userData;

    b2Body* bodyA;

    b2Body* bodyB;

    bool collideConnected;
};

class b2Joint
{
public:

    b2JointType GetType() const;

    b2Body* GetBodyA();

    b2Body* GetBodyB();

    virtual b2Vec2 GetAnchorA() const = 0;

    virtual b2Vec2 GetAnchorB() const = 0;

    virtual b2Vec2 GetReactionForce(float32 inv_dt) const = 0;

    virtual float32 GetReactionTorque(float32 inv_dt) const = 0;

    b2Joint* GetNext();
    const b2Joint* GetNext() const;

    void* GetUserData() const;

    void SetUserData(void* data);

    bool IsActive() const;

    bool GetCollideConnected() const;

    virtual void Dump() { b2Log("// Dump is not supported for this joint type.\n"); }

    virtual void ShiftOrigin(const b2Vec2& newOrigin) { B2_NOT_USED(newOrigin);  }

protected:
    friend class b2World;
    friend class b2Body;
    friend class b2Island;
    friend class b2GearJoint;

    static b2Joint* Create(const b2JointDef* def, b2BlockAllocator* allocator);
    static void Destroy(b2Joint* joint, b2BlockAllocator* allocator);

    b2Joint(const b2JointDef* def);
    virtual ~b2Joint() {}

    virtual void InitVelocityConstraints(const b2SolverData& data) = 0;
    virtual void SolveVelocityConstraints(const b2SolverData& data) = 0;

    // This returns true if the position errors are within tolerance.
    virtual bool SolvePositionConstraints(const b2SolverData& data) = 0;

    b2JointType m_type;
    b2Joint* m_prev;
    b2Joint* m_next;
    b2JointEdge m_edgeA;
    b2JointEdge m_edgeB;
    b2Body* m_bodyA;
    b2Body* m_bodyB;

    int32 m_index;

    bool m_islandFlag;
    bool m_collideConnected;

    void* m_userData;
};

inline b2JointType b2Joint::GetType() const
{
    return m_type;
}

inline b2Body* b2Joint::GetBodyA()
{
    return m_bodyA;
}

inline b2Body* b2Joint::GetBodyB()
{
    return m_bodyB;
}

inline b2Joint* b2Joint::GetNext()
{
    return m_next;
}

inline const b2Joint* b2Joint::GetNext() const
{
    return m_next;
}

inline void* b2Joint::GetUserData() const
{
    return m_userData;
}

inline void b2Joint::SetUserData(void* data)
{
    m_userData = data;
}

inline bool b2Joint::GetCollideConnected() const
{
    return m_collideConnected;
}

#endif