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+/*
+* 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 friction to zero.
+/// For example, anything slides on ice.
+inline float32 b2MixFriction(float32 friction1, float32 friction2)
+{
+ return b2Sqrt(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();
+
+ /// Set the desired tangent speed for a conveyor belt behavior. In meters per second.
+ void SetTangentSpeed(float32 speed);
+
+ /// Get the desired tangent speed. In meters per second.
+ float32 GetTangentSpeed() const;
+
+ /// 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(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;
+ float32 m_toi;
+
+ float32 m_friction;
+ float32 m_restitution;
+
+ float32 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(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);
+}
+
+inline void b2Contact::SetTangentSpeed(float32 speed)
+{
+ m_tangentSpeed = speed;
+}
+
+inline float32 b2Contact::GetTangentSpeed() const
+{
+ return m_tangentSpeed;
+}
+
+#endif