/* * Copyright (c) 2006-2009 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_CONTACT_H #define B2_CONTACT_H #include <Box2D/Common/b2Math.h> #include <Box2D/Collision/b2Collision.h> #include <Box2D/Collision/Shapes/b2Shape.h> #include <Box2D/Dynamics/b2Fixture.h> class b2Body; class b2Contact; class b2Fixture; class b2World; class b2BlockAllocator; class b2StackAllocator; class b2ContactListener; /// Friction mixing law. The idea is to allow either fixture to drive the restitution to zero. /// For example, anything slides on ice. inline float32 b2MixFriction(float32 friction1, float32 friction2) { return std::sqrt(friction1 * friction2); } /// Restitution mixing law. The idea is allow for anything to bounce off an inelastic surface. /// For example, a superball bounces on anything. inline float32 b2MixRestitution(float32 restitution1, float32 restitution2) { return restitution1 > restitution2 ? restitution1 : restitution2; } typedef b2Contact* b2ContactCreateFcn( b2Fixture* fixtureA, int32 indexA, b2Fixture* fixtureB, int32 indexB, b2BlockAllocator* allocator); typedef void b2ContactDestroyFcn(b2Contact* contact, b2BlockAllocator* allocator); struct b2ContactRegister { b2ContactCreateFcn* createFcn; b2ContactDestroyFcn* destroyFcn; bool primary; }; /// A contact edge is used to connect bodies and contacts together /// in a contact graph where each body is a node and each contact /// is an edge. A contact edge belongs to a doubly linked list /// maintained in each attached body. Each contact has two contact /// nodes, one for each attached body. struct b2ContactEdge { b2Body* other; ///< provides quick access to the other body attached. b2Contact* contact; ///< the contact b2ContactEdge* prev; ///< the previous contact edge in the body's contact list b2ContactEdge* next; ///< the next contact edge in the body's contact list }; /// The class manages contact between two shapes. A contact exists for each overlapping /// AABB in the broad-phase (except if filtered). Therefore a contact object may exist /// that has no contact points. class b2Contact { public: /// Get the contact manifold. Do not modify the manifold unless you understand the /// internals of Box2D. b2Manifold* GetManifold(); const b2Manifold* GetManifold() const; /// Get the world manifold. void GetWorldManifold(b2WorldManifold* worldManifold) const; /// Is this contact touching? bool IsTouching() const; /// Enable/disable this contact. This can be used inside the pre-solve /// contact listener. The contact is only disabled for the current /// time step (or sub-step in continuous collisions). void SetEnabled(bool flag); /// Has this contact been disabled? bool IsEnabled() const; /// Get the next contact in the world's contact list. b2Contact* GetNext(); const b2Contact* GetNext() const; /// Get fixture A in this contact. b2Fixture* GetFixtureA(); const b2Fixture* GetFixtureA() const; /// Get the child primitive index for fixture A. int32 GetChildIndexA() const; /// Get fixture B in this contact. b2Fixture* GetFixtureB(); const b2Fixture* GetFixtureB() const; /// Get the child primitive index for fixture B. int32 GetChildIndexB() const; /// Override the default friction mixture. You can call this in b2ContactListener::PreSolve. /// This value persists until set or reset. void SetFriction(float32 friction); /// Get the friction. float32 GetFriction() const; /// Reset the friction mixture to the default value. void ResetFriction(); /// Override the default restitution mixture. You can call this in b2ContactListener::PreSolve. /// The value persists until you set or reset. void SetRestitution(float32 restitution); /// Get the restitution. float32 GetRestitution() const; /// Reset the restitution to the default value. void ResetRestitution(); /// Evaluate this contact with your own manifold and transforms. 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 }; /// Flag this contact for filtering. Filtering will occur the next time step. 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(NULL), m_fixtureB(NULL) {} 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; float32 m_toi; float32 m_friction; float32 m_restitution; }; 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(float32 friction) { m_friction = friction; } inline float32 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(float32 restitution) { m_restitution = restitution; } inline float32 b2Contact::GetRestitution() const { return m_restitution; } inline void b2Contact::ResetRestitution() { m_restitution = b2MixRestitution(m_fixtureA->m_restitution, m_fixtureB->m_restitution); } #endif