b2_contact.h

Go to the documentation of this file.

// 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_CONTACT_H
#define B2_CONTACT_H

#include "b2_api.h"
#include "b2_collision.h"
#include "b2_fixture.h"
#include "b2_math.h"
#include "b2_shape.h"

class b2Body;
class b2Contact;
class b2Fixture;
class b2World;
class b2BlockAllocator;
class b2StackAllocator;
class b2ContactListener;

inline float b2MixFriction(float friction1, float friction2)
{
        return b2Sqrt(friction1 * friction2);
}

inline float b2MixRestitution(float restitution1, float restitution2)
{
        return restitution1 > restitution2 ? restitution1 : restitution2;
}

inline float b2MixRestitutionThreshold(float threshold1, float threshold2)
{
        return threshold1 < threshold2 ? threshold1 : threshold2;
}

typedef b2Contact* b2ContactCreateFcn(  b2Fixture* fixtureA, int32 indexA,
                                                                                b2Fixture* fixtureB, int32 indexB,
                                                                                b2BlockAllocator* allocator);
typedef void b2ContactDestroyFcn(b2Contact* contact, b2BlockAllocator* allocator);

struct B2_API b2ContactRegister
{
        b2ContactCreateFcn* createFcn;
        b2ContactDestroyFcn* destroyFcn;
        bool primary;
};

struct B2_API b2ContactEdge
{
        b2Body* other;                  
        b2Contact* contact;             
        b2ContactEdge* prev;    
        b2ContactEdge* next;    
};

class B2_API b2Contact
{
public:

        b2Manifold* GetManifold();
        const b2Manifold* GetManifold() const;

        void GetWorldManifold(b2WorldManifold* worldManifold) const;

        bool IsTouching() const;

        void SetEnabled(bool flag);

        bool IsEnabled() const;

        b2Contact* GetNext();
        const b2Contact* GetNext() const;

        b2Fixture* GetFixtureA();
        const b2Fixture* GetFixtureA() const;

        int32 GetChildIndexA() const;

        b2Fixture* GetFixtureB();
        const b2Fixture* GetFixtureB() const;

        int32 GetChildIndexB() const;

        void SetFriction(float friction);

        float GetFriction() const;

        void ResetFriction();

        void SetRestitution(float restitution);

        float GetRestitution() const;

        void ResetRestitution();

        void SetRestitutionThreshold(float threshold);

        float GetRestitutionThreshold() const;

        void ResetRestitutionThreshold();

        void SetTangentSpeed(float speed);

        float GetTangentSpeed() const;

        virtual void Evaluate(b2Manifold* manifold, const b2Transform& xfA, const b2Transform& xfB) = 0;

protected:
        friend class b2ContactManager;
        friend class b2World;
        friend class b2ContactSolver;
        friend class b2Body;
        friend class b2Fixture;

        // Flags stored in m_flags
        enum
        {
                // Used when crawling contact graph when forming islands.
                e_islandFlag            = 0x0001,

                // Set when the shapes are touching.
                e_touchingFlag          = 0x0002,

                // This contact can be disabled (by user)
                e_enabledFlag           = 0x0004,

                // This contact needs filtering because a fixture filter was changed.
                e_filterFlag            = 0x0008,

                // This bullet contact had a TOI event
                e_bulletHitFlag         = 0x0010,

                // This contact has a valid TOI in m_toi
                e_toiFlag                       = 0x0020
        };

        void FlagForFiltering();

        static void AddType(b2ContactCreateFcn* createFcn, b2ContactDestroyFcn* destroyFcn,
                                                b2Shape::Type typeA, b2Shape::Type typeB);
        static void InitializeRegisters();
        static b2Contact* Create(b2Fixture* fixtureA, int32 indexA, b2Fixture* fixtureB, int32 indexB, b2BlockAllocator* allocator);
        static void Destroy(b2Contact* contact, b2Shape::Type typeA, b2Shape::Type typeB, b2BlockAllocator* allocator);
        static void Destroy(b2Contact* contact, b2BlockAllocator* allocator);

        b2Contact() : m_fixtureA(nullptr), m_fixtureB(nullptr) {}
        b2Contact(b2Fixture* fixtureA, int32 indexA, b2Fixture* fixtureB, int32 indexB);
        virtual ~b2Contact() {}

        void Update(b2ContactListener* listener);

        static b2ContactRegister s_registers[b2Shape::e_typeCount][b2Shape::e_typeCount];
        static bool s_initialized;

        uint32 m_flags;

        // World pool and list pointers.
        b2Contact* m_prev;
        b2Contact* m_next;

        // Nodes for connecting bodies.
        b2ContactEdge m_nodeA;
        b2ContactEdge m_nodeB;

        b2Fixture* m_fixtureA;
        b2Fixture* m_fixtureB;

        int32 m_indexA;
        int32 m_indexB;

        b2Manifold m_manifold;

        int32 m_toiCount;
        float m_toi;

        float m_friction;
        float m_restitution;
        float m_restitutionThreshold;

        float m_tangentSpeed;
};

inline b2Manifold* b2Contact::GetManifold()
{
        return &m_manifold;
}

inline const b2Manifold* b2Contact::GetManifold() const
{
        return &m_manifold;
}

inline void b2Contact::GetWorldManifold(b2WorldManifold* worldManifold) const
{
        const b2Body* bodyA = m_fixtureA->GetBody();
        const b2Body* bodyB = m_fixtureB->GetBody();
        const b2Shape* shapeA = m_fixtureA->GetShape();
        const b2Shape* shapeB = m_fixtureB->GetShape();

        worldManifold->Initialize(&m_manifold, bodyA->GetTransform(), shapeA->m_radius, bodyB->GetTransform(), shapeB->m_radius);
}

inline void b2Contact::SetEnabled(bool flag)
{
        if (flag)
        {
                m_flags |= e_enabledFlag;
        }
        else
        {
                m_flags &= ~e_enabledFlag;
        }
}

inline bool b2Contact::IsEnabled() const
{
        return (m_flags & e_enabledFlag) == e_enabledFlag;
}

inline bool b2Contact::IsTouching() const
{
        return (m_flags & e_touchingFlag) == e_touchingFlag;
}

inline b2Contact* b2Contact::GetNext()
{
        return m_next;
}

inline const b2Contact* b2Contact::GetNext() const
{
        return m_next;
}

inline b2Fixture* b2Contact::GetFixtureA()
{
        return m_fixtureA;
}

inline const b2Fixture* b2Contact::GetFixtureA() const
{
        return m_fixtureA;
}

inline b2Fixture* b2Contact::GetFixtureB()
{
        return m_fixtureB;
}

inline int32 b2Contact::GetChildIndexA() const
{
        return m_indexA;
}

inline const b2Fixture* b2Contact::GetFixtureB() const
{
        return m_fixtureB;
}

inline int32 b2Contact::GetChildIndexB() const
{
        return m_indexB;
}

inline void b2Contact::FlagForFiltering()
{
        m_flags |= e_filterFlag;
}

inline void b2Contact::SetFriction(float friction)
{
        m_friction = friction;
}

inline float b2Contact::GetFriction() const
{
        return m_friction;
}

inline void b2Contact::ResetFriction()
{
        m_friction = b2MixFriction(m_fixtureA->m_friction, m_fixtureB->m_friction);
}

inline void b2Contact::SetRestitution(float restitution)
{
        m_restitution = restitution;
}

inline float b2Contact::GetRestitution() const
{
        return m_restitution;
}

inline void b2Contact::ResetRestitution()
{
        m_restitution = b2MixRestitution(m_fixtureA->m_restitution, m_fixtureB->m_restitution);
}

inline void b2Contact::SetRestitutionThreshold(float threshold)
{
        m_restitutionThreshold = threshold;
}

inline float b2Contact::GetRestitutionThreshold() const
{
        return m_restitutionThreshold;
}

inline void b2Contact::ResetRestitutionThreshold()
{
        m_restitutionThreshold = b2MixRestitutionThreshold(m_fixtureA->m_restitutionThreshold, m_fixtureB->m_restitutionThreshold);
}

inline void b2Contact::SetTangentSpeed(float speed)
{
        m_tangentSpeed = speed;
}

inline float b2Contact::GetTangentSpeed() const
{
        return m_tangentSpeed;
}

#endif