b2_joint.h

// 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_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();
    const b2JointUserData& GetUserData() const;
 
    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 const b2JointUserData& b2Joint::GetUserData() const
{
    return m_userData;
}
 
inline bool b2Joint::GetCollideConnected() const
{
    return m_collideConnected;
}
 
#endif