b2Contact.cpp

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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.
*/

#include <Box2D/Dynamics/Contacts/b2Contact.h>
#include <Box2D/Dynamics/Contacts/b2CircleContact.h>
#include <Box2D/Dynamics/Contacts/b2PolygonAndCircleContact.h>
#include <Box2D/Dynamics/Contacts/b2PolygonContact.h>
#include <Box2D/Dynamics/Contacts/b2EdgeAndCircleContact.h>
#include <Box2D/Dynamics/Contacts/b2EdgeAndPolygonContact.h>
#include <Box2D/Dynamics/Contacts/b2ChainAndCircleContact.h>
#include <Box2D/Dynamics/Contacts/b2ChainAndPolygonContact.h>
#include <Box2D/Dynamics/Contacts/b2ContactSolver.h>

#include <Box2D/Collision/b2Collision.h>
#include <Box2D/Collision/b2TimeOfImpact.h>
#include <Box2D/Collision/Shapes/b2Shape.h>
#include <Box2D/Common/b2BlockAllocator.h>
#include <Box2D/Dynamics/b2Body.h>
#include <Box2D/Dynamics/b2Fixture.h>
#include <Box2D/Dynamics/b2World.h>

b2ContactRegister b2Contact::s_registers[b2Shape::e_typeCount][b2Shape::e_typeCount];
bool b2Contact::s_initialized = false;

void b2Contact::InitializeRegisters()
{
        AddType(b2CircleContact::Create, b2CircleContact::Destroy, b2Shape::e_circle, b2Shape::e_circle);
        AddType(b2PolygonAndCircleContact::Create, b2PolygonAndCircleContact::Destroy, b2Shape::e_polygon, b2Shape::e_circle);
        AddType(b2PolygonContact::Create, b2PolygonContact::Destroy, b2Shape::e_polygon, b2Shape::e_polygon);
        AddType(b2EdgeAndCircleContact::Create, b2EdgeAndCircleContact::Destroy, b2Shape::e_edge, b2Shape::e_circle);
        AddType(b2EdgeAndPolygonContact::Create, b2EdgeAndPolygonContact::Destroy, b2Shape::e_edge, b2Shape::e_polygon);
        AddType(b2ChainAndCircleContact::Create, b2ChainAndCircleContact::Destroy, b2Shape::e_chain, b2Shape::e_circle);
        AddType(b2ChainAndPolygonContact::Create, b2ChainAndPolygonContact::Destroy, b2Shape::e_chain, b2Shape::e_polygon);
}

void b2Contact::AddType(b2ContactCreateFcn* createFcn, b2ContactDestroyFcn* destoryFcn,
                                                b2Shape::Type type1, b2Shape::Type type2)
{
        b2Assert(0 <= type1 && type1 < b2Shape::e_typeCount);
        b2Assert(0 <= type2 && type2 < b2Shape::e_typeCount);
        
        s_registers[type1][type2].createFcn = createFcn;
        s_registers[type1][type2].destroyFcn = destoryFcn;
        s_registers[type1][type2].primary = true;

        if (type1 != type2)
        {
                s_registers[type2][type1].createFcn = createFcn;
                s_registers[type2][type1].destroyFcn = destoryFcn;
                s_registers[type2][type1].primary = false;
        }
}

b2Contact* b2Contact::Create(b2Fixture* fixtureA, int32 indexA, b2Fixture* fixtureB, int32 indexB, b2BlockAllocator* allocator)
{
        if (s_initialized == false)
        {
                InitializeRegisters();
                s_initialized = true;
        }

        b2Shape::Type type1 = fixtureA->GetType();
        b2Shape::Type type2 = fixtureB->GetType();

        b2Assert(0 <= type1 && type1 < b2Shape::e_typeCount);
        b2Assert(0 <= type2 && type2 < b2Shape::e_typeCount);
        
        b2ContactCreateFcn* createFcn = s_registers[type1][type2].createFcn;
        if (createFcn)
        {
                if (s_registers[type1][type2].primary)
                {
                        return createFcn(fixtureA, indexA, fixtureB, indexB, allocator);
                }
                else
                {
                        return createFcn(fixtureB, indexB, fixtureA, indexA, allocator);
                }
        }
        else
        {
                return NULL;
        }
}

void b2Contact::Destroy(b2Contact* contact, b2BlockAllocator* allocator)
{
        b2Assert(s_initialized == true);

        b2Fixture* fixtureA = contact->m_fixtureA;
        b2Fixture* fixtureB = contact->m_fixtureB;

        if (contact->m_manifold.pointCount > 0 &&
                fixtureA->IsSensor() == false &&
                fixtureB->IsSensor() == false)
        {
                fixtureA->GetBody()->SetAwake(true);
                fixtureB->GetBody()->SetAwake(true);
        }

        b2Shape::Type typeA = fixtureA->GetType();
        b2Shape::Type typeB = fixtureB->GetType();

        b2Assert(0 <= typeA && typeB < b2Shape::e_typeCount);
        b2Assert(0 <= typeA && typeB < b2Shape::e_typeCount);

        b2ContactDestroyFcn* destroyFcn = s_registers[typeA][typeB].destroyFcn;
        destroyFcn(contact, allocator);
}

b2Contact::b2Contact(b2Fixture* fA, int32 indexA, b2Fixture* fB, int32 indexB)
{
        m_flags = e_enabledFlag;

        m_fixtureA = fA;
        m_fixtureB = fB;

        m_indexA = indexA;
        m_indexB = indexB;

        m_manifold.pointCount = 0;

        m_prev = NULL;
        m_next = NULL;

        m_nodeA.contact = NULL;
        m_nodeA.prev = NULL;
        m_nodeA.next = NULL;
        m_nodeA.other = NULL;

        m_nodeB.contact = NULL;
        m_nodeB.prev = NULL;
        m_nodeB.next = NULL;
        m_nodeB.other = NULL;

        m_toiCount = 0;

        m_friction = b2MixFriction(m_fixtureA->m_friction, m_fixtureB->m_friction);
        m_restitution = b2MixRestitution(m_fixtureA->m_restitution, m_fixtureB->m_restitution);

        m_tangentSpeed = 0.0f;
}

// Update the contact manifold and touching status.
// Note: do not assume the fixture AABBs are overlapping or are valid.
void b2Contact::Update(b2ContactListener* listener)
{
        b2Manifold oldManifold = m_manifold;

        // Re-enable this contact.
        m_flags |= e_enabledFlag;

        bool touching = false;
        bool wasTouching = (m_flags & e_touchingFlag) == e_touchingFlag;

        bool sensorA = m_fixtureA->IsSensor();
        bool sensorB = m_fixtureB->IsSensor();
        bool sensor = sensorA || sensorB;

        b2Body* bodyA = m_fixtureA->GetBody();
        b2Body* bodyB = m_fixtureB->GetBody();
        const b2Transform& xfA = bodyA->GetTransform();
        const b2Transform& xfB = bodyB->GetTransform();

        // Is this contact a sensor?
        if (sensor)
        {
                const b2Shape* shapeA = m_fixtureA->GetShape();
                const b2Shape* shapeB = m_fixtureB->GetShape();
                touching = b2TestOverlap(shapeA, m_indexA, shapeB, m_indexB, xfA, xfB);

                // Sensors don't generate manifolds.
                m_manifold.pointCount = 0;
        }
        else
        {
                Evaluate(&m_manifold, xfA, xfB);
                touching = m_manifold.pointCount > 0;

                // Match old contact ids to new contact ids and copy the
                // stored impulses to warm start the solver.
                for (int32 i = 0; i < m_manifold.pointCount; ++i)
                {
                        b2ManifoldPoint* mp2 = m_manifold.points + i;
                        mp2->normalImpulse = 0.0f;
                        mp2->tangentImpulse = 0.0f;
                        b2ContactID id2 = mp2->id;

                        for (int32 j = 0; j < oldManifold.pointCount; ++j)
                        {
                                b2ManifoldPoint* mp1 = oldManifold.points + j;

                                if (mp1->id.key == id2.key)
                                {
                                        mp2->normalImpulse = mp1->normalImpulse;
                                        mp2->tangentImpulse = mp1->tangentImpulse;
                                        break;
                                }
                        }
                }

                if (touching != wasTouching)
                {
                        bodyA->SetAwake(true);
                        bodyB->SetAwake(true);
                }
        }

        if (touching)
        {
                m_flags |= e_touchingFlag;
        }
        else
        {
                m_flags &= ~e_touchingFlag;
        }

        if (wasTouching == false && touching == true && listener)
        {
                listener->BeginContact(this);
        }

        if (wasTouching == true && touching == false && listener)
        {
                listener->EndContact(this);
        }

        if (sensor == false && touching && listener)
        {
                listener->PreSolve(this, &oldManifold);
        }
}