b2_joint.h

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// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#ifndef B2_JOINT_H
#define B2_JOINT_H

#include "b2_api.h"
#include "b2_math.h"

class b2Body;
class b2Draw;
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
};

struct B2_API b2Jacobian
{
        b2Vec2 linear;
        float angularA;
        float angularB;
};

struct B2_API b2JointEdge
{
        b2Body* other;                  
        b2Joint* joint;                 
        b2JointEdge* prev;              
        b2JointEdge* next;              
};

struct B2_API b2JointDef
{
        b2JointDef()
        {
                type = e_unknownJoint;
                bodyA = nullptr;
                bodyB = nullptr;
                collideConnected = false;
        }

        b2JointType type;

        b2JointUserData userData;

        b2Body* bodyA;

        b2Body* bodyB;

        bool collideConnected;
};

B2_API void b2LinearStiffness(float& stiffness, float& damping,
        float frequencyHertz, float dampingRatio,
        const b2Body* bodyA, const b2Body* bodyB);

B2_API void b2AngularStiffness(float& stiffness, float& damping,
        float frequencyHertz, float dampingRatio,
        const b2Body* bodyA, const b2Body* bodyB);

class B2_API b2Joint
{
public:

        b2JointType GetType() const;

        b2Body* GetBodyA();

        b2Body* GetBodyB();

        virtual b2Vec2 GetAnchorA() const = 0;

        virtual b2Vec2 GetAnchorB() const = 0;

        virtual b2Vec2 GetReactionForce(float inv_dt) const = 0;

        virtual float GetReactionTorque(float inv_dt) const = 0;

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

        b2JointUserData& GetUserData();

        bool IsEnabled() const;

        bool GetCollideConnected() const;

        virtual void Dump() { b2Dump("// Dump is not supported for this joint type.\n"); }

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

        virtual void Draw(b2Draw* draw) const;

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;

        b2JointUserData 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 b2JointUserData& b2Joint::GetUserData()
{
        return m_userData;
}

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

#endif