b2Body.cpp

Go to the documentation of this file.

/*
* Copyright (c) 2006-2007 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/b2Body.h>
#include <Box2D/Dynamics/b2Fixture.h>
#include <Box2D/Dynamics/b2World.h>
#include <Box2D/Dynamics/Contacts/b2Contact.h>
#include <Box2D/Dynamics/Joints/b2Joint.h>

b2Body::b2Body(const b2BodyDef* bd, b2World* world)
{
        b2Assert(bd->position.IsValid());
        b2Assert(bd->linearVelocity.IsValid());
        b2Assert(b2IsValid(bd->angle));
        b2Assert(b2IsValid(bd->angularVelocity));
        b2Assert(b2IsValid(bd->angularDamping) && bd->angularDamping >= 0.0f);
        b2Assert(b2IsValid(bd->linearDamping) && bd->linearDamping >= 0.0f);

        m_flags = 0;

        if (bd->bullet)
        {
                m_flags |= e_bulletFlag;
        }
        if (bd->fixedRotation)
        {
                m_flags |= e_fixedRotationFlag;
        }
        if (bd->allowSleep)
        {
                m_flags |= e_autoSleepFlag;
        }
        if (bd->awake)
        {
                m_flags |= e_awakeFlag;
        }
        if (bd->active)
        {
                m_flags |= e_activeFlag;
        }

        m_world = world;

        m_xf.p = bd->position;
        m_xf.q.Set(bd->angle);

        m_sweep.localCenter.SetZero();
        m_sweep.c0 = m_xf.p;
        m_sweep.c = m_xf.p;
        m_sweep.a0 = bd->angle;
        m_sweep.a = bd->angle;
        m_sweep.alpha0 = 0.0f;

        m_jointList = NULL;
        m_contactList = NULL;
        m_prev = NULL;
        m_next = NULL;

        m_linearVelocity = bd->linearVelocity;
        m_angularVelocity = bd->angularVelocity;

        m_linearDamping = bd->linearDamping;
        m_angularDamping = bd->angularDamping;
        m_gravityScale = bd->gravityScale;

        m_force.SetZero();
        m_torque = 0.0f;

        m_sleepTime = 0.0f;

        m_type = bd->type;

        if (m_type == b2_dynamicBody)
        {
                m_mass = 1.0f;
                m_invMass = 1.0f;
        }
        else
        {
                m_mass = 0.0f;
                m_invMass = 0.0f;
        }

        m_I = 0.0f;
        m_invI = 0.0f;

        m_userData = bd->userData;

        m_fixtureList = NULL;
        m_fixtureCount = 0;
}

b2Body::~b2Body()
{
        // shapes and joints are destroyed in b2World::Destroy
}

void b2Body::SetType(b2BodyType type)
{
        b2Assert(m_world->IsLocked() == false);
        if (m_world->IsLocked() == true)
        {
                return;
        }

        if (m_type == type)
        {
                return;
        }

        m_type = type;

        ResetMassData();

        if (m_type == b2_staticBody)
        {
                m_linearVelocity.SetZero();
                m_angularVelocity = 0.0f;
                m_sweep.a0 = m_sweep.a;
                m_sweep.c0 = m_sweep.c;
                SynchronizeFixtures();
        }

        SetAwake(true);

        m_force.SetZero();
        m_torque = 0.0f;

        // Delete the attached contacts.
        b2ContactEdge* ce = m_contactList;
        while (ce)
        {
                b2ContactEdge* ce0 = ce;
                ce = ce->next;
                m_world->m_contactManager.Destroy(ce0->contact);
        }
        m_contactList = NULL;

        // Touch the proxies so that new contacts will be created (when appropriate)
        b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
        for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
        {
                int32 proxyCount = f->m_proxyCount;
                for (int32 i = 0; i < proxyCount; ++i)
                {
                        broadPhase->TouchProxy(f->m_proxies[i].proxyId);
                }
        }
}

b2Fixture* b2Body::CreateFixture(const b2FixtureDef* def)
{
        b2Assert(m_world->IsLocked() == false);
        if (m_world->IsLocked() == true)
        {
                return NULL;
        }

        b2BlockAllocator* allocator = &m_world->m_blockAllocator;

        void* memory = allocator->Allocate(sizeof(b2Fixture));
        b2Fixture* fixture = new (memory) b2Fixture;
        fixture->Create(allocator, this, def);

        if (m_flags & e_activeFlag)
        {
                b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
                fixture->CreateProxies(broadPhase, m_xf);
        }

        fixture->m_next = m_fixtureList;
        m_fixtureList = fixture;
        ++m_fixtureCount;

        fixture->m_body = this;

        // Adjust mass properties if needed.
        if (fixture->m_density > 0.0f)
        {
                ResetMassData();
        }

        // Let the world know we have a new fixture. This will cause new contacts
        // to be created at the beginning of the next time step.
        m_world->m_flags |= b2World::e_newFixture;

        return fixture;
}

b2Fixture* b2Body::CreateFixture(const b2Shape* shape, float32 density)
{
        b2FixtureDef def;
        def.shape = shape;
        def.density = density;

        return CreateFixture(&def);
}

void b2Body::DestroyFixture(b2Fixture* fixture)
{
        b2Assert(m_world->IsLocked() == false);
        if (m_world->IsLocked() == true)
        {
                return;
        }

        b2Assert(fixture->m_body == this);

        // Remove the fixture from this body's singly linked list.
        b2Assert(m_fixtureCount > 0);
        b2Fixture** node = &m_fixtureList;
        bool found = false;
        while (*node != NULL)
        {
                if (*node == fixture)
                {
                        *node = fixture->m_next;
                        found = true;
                        break;
                }

                node = &(*node)->m_next;
        }

        // You tried to remove a shape that is not attached to this body.
        b2Assert(found);

        // Destroy any contacts associated with the fixture.
        b2ContactEdge* edge = m_contactList;
        while (edge)
        {
                b2Contact* c = edge->contact;
                edge = edge->next;

                b2Fixture* fixtureA = c->GetFixtureA();
                b2Fixture* fixtureB = c->GetFixtureB();

                if (fixture == fixtureA || fixture == fixtureB)
                {
                        // This destroys the contact and removes it from
                        // this body's contact list.
                        m_world->m_contactManager.Destroy(c);
                }
        }

        b2BlockAllocator* allocator = &m_world->m_blockAllocator;

        if (m_flags & e_activeFlag)
        {
                b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
                fixture->DestroyProxies(broadPhase);
        }

        fixture->Destroy(allocator);
        fixture->m_body = NULL;
        fixture->m_next = NULL;
        fixture->~b2Fixture();
        allocator->Free(fixture, sizeof(b2Fixture));

        --m_fixtureCount;

        // Reset the mass data.
        ResetMassData();
}

void b2Body::ResetMassData()
{
        // Compute mass data from shapes. Each shape has its own density.
        m_mass = 0.0f;
        m_invMass = 0.0f;
        m_I = 0.0f;
        m_invI = 0.0f;
        m_sweep.localCenter.SetZero();

        // Static and kinematic bodies have zero mass.
        if (m_type == b2_staticBody || m_type == b2_kinematicBody)
        {
                m_sweep.c0 = m_xf.p;
                m_sweep.c = m_xf.p;
                m_sweep.a0 = m_sweep.a;
                return;
        }

        b2Assert(m_type == b2_dynamicBody);

        // Accumulate mass over all fixtures.
        b2Vec2 localCenter = b2Vec2_zero;
        for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
        {
                if (f->m_density == 0.0f)
                {
                        continue;
                }

                b2MassData massData;
                f->GetMassData(&massData);
                m_mass += massData.mass;
                localCenter += massData.mass * massData.center;
                m_I += massData.I;
        }

        // Compute center of mass.
        if (m_mass > 0.0f)
        {
                m_invMass = 1.0f / m_mass;
                localCenter *= m_invMass;
        }
        else
        {
                // Force all dynamic bodies to have a positive mass.
                m_mass = 1.0f;
                m_invMass = 1.0f;
        }

        if (m_I > 0.0f && (m_flags & e_fixedRotationFlag) == 0)
        {
                // Center the inertia about the center of mass.
                m_I -= m_mass * b2Dot(localCenter, localCenter);
                b2Assert(m_I > 0.0f);
                m_invI = 1.0f / m_I;

        }
        else
        {
                m_I = 0.0f;
                m_invI = 0.0f;
        }

        // Move center of mass.
        b2Vec2 oldCenter = m_sweep.c;
        m_sweep.localCenter = localCenter;
        m_sweep.c0 = m_sweep.c = b2Mul(m_xf, m_sweep.localCenter);

        // Update center of mass velocity.
        m_linearVelocity += b2Cross(m_angularVelocity, m_sweep.c - oldCenter);
}

void b2Body::SetMassData(const b2MassData* massData)
{
        b2Assert(m_world->IsLocked() == false);
        if (m_world->IsLocked() == true)
        {
                return;
        }

        if (m_type != b2_dynamicBody)
        {
                return;
        }

        m_invMass = 0.0f;
        m_I = 0.0f;
        m_invI = 0.0f;

        m_mass = massData->mass;
        if (m_mass <= 0.0f)
        {
                m_mass = 1.0f;
        }

        m_invMass = 1.0f / m_mass;

        if (massData->I > 0.0f && (m_flags & b2Body::e_fixedRotationFlag) == 0)
        {
                m_I = massData->I - m_mass * b2Dot(massData->center, massData->center);
                b2Assert(m_I > 0.0f);
                m_invI = 1.0f / m_I;
        }

        // Move center of mass.
        b2Vec2 oldCenter = m_sweep.c;
        m_sweep.localCenter =  massData->center;
        m_sweep.c0 = m_sweep.c = b2Mul(m_xf, m_sweep.localCenter);

        // Update center of mass velocity.
        m_linearVelocity += b2Cross(m_angularVelocity, m_sweep.c - oldCenter);
}

bool b2Body::ShouldCollide(const b2Body* other) const
{
        // At least one body should be dynamic.
        if (m_type != b2_dynamicBody && other->m_type != b2_dynamicBody)
        {
                return false;
        }

        // Does a joint prevent collision?
        for (b2JointEdge* jn = m_jointList; jn; jn = jn->next)
        {
                if (jn->other == other)
                {
                        if (jn->joint->m_collideConnected == false)
                        {
                                return false;
                        }
                }
        }

        return true;
}

void b2Body::SetTransform(const b2Vec2& position, float32 angle)
{
        b2Assert(m_world->IsLocked() == false);
        if (m_world->IsLocked() == true)
        {
                return;
        }

        m_xf.q.Set(angle);
        m_xf.p = position;

        m_sweep.c = b2Mul(m_xf, m_sweep.localCenter);
        m_sweep.a = angle;

        m_sweep.c0 = m_sweep.c;
        m_sweep.a0 = angle;

        b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
        for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
        {
                f->Synchronize(broadPhase, m_xf, m_xf);
        }
}

void b2Body::SynchronizeFixtures()
{
        b2Transform xf1;
        xf1.q.Set(m_sweep.a0);
        xf1.p = m_sweep.c0 - b2Mul(xf1.q, m_sweep.localCenter);

        b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
        for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
        {
                f->Synchronize(broadPhase, xf1, m_xf);
        }
}

void b2Body::SetActive(bool flag)
{
        b2Assert(m_world->IsLocked() == false);

        if (flag == IsActive())
        {
                return;
        }

        if (flag)
        {
                m_flags |= e_activeFlag;

                // Create all proxies.
                b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
                for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
                {
                        f->CreateProxies(broadPhase, m_xf);
                }

                // Contacts are created the next time step.
        }
        else
        {
                m_flags &= ~e_activeFlag;

                // Destroy all proxies.
                b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
                for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
                {
                        f->DestroyProxies(broadPhase);
                }

                // Destroy the attached contacts.
                b2ContactEdge* ce = m_contactList;
                while (ce)
                {
                        b2ContactEdge* ce0 = ce;
                        ce = ce->next;
                        m_world->m_contactManager.Destroy(ce0->contact);
                }
                m_contactList = NULL;
        }
}

void b2Body::SetFixedRotation(bool flag)
{
        bool status = (m_flags & e_fixedRotationFlag) == e_fixedRotationFlag;
        if (status == flag)
        {
                return;
        }

        if (flag)
        {
                m_flags |= e_fixedRotationFlag;
        }
        else
        {
                m_flags &= ~e_fixedRotationFlag;
        }

        m_angularVelocity = 0.0f;

        ResetMassData();
}

void b2Body::Dump()
{
        int32 bodyIndex = m_islandIndex;

        b2Log("{\n");
        b2Log("  b2BodyDef bd;\n");
        b2Log("  bd.type = b2BodyType(%d);\n", m_type);
        b2Log("  bd.position.Set(%.15lef, %.15lef);\n", m_xf.p.x, m_xf.p.y);
        b2Log("  bd.angle = %.15lef;\n", m_sweep.a);
        b2Log("  bd.linearVelocity.Set(%.15lef, %.15lef);\n", m_linearVelocity.x, m_linearVelocity.y);
        b2Log("  bd.angularVelocity = %.15lef;\n", m_angularVelocity);
        b2Log("  bd.linearDamping = %.15lef;\n", m_linearDamping);
        b2Log("  bd.angularDamping = %.15lef;\n", m_angularDamping);
        b2Log("  bd.allowSleep = bool(%d);\n", m_flags & e_autoSleepFlag);
        b2Log("  bd.awake = bool(%d);\n", m_flags & e_awakeFlag);
        b2Log("  bd.fixedRotation = bool(%d);\n", m_flags & e_fixedRotationFlag);
        b2Log("  bd.bullet = bool(%d);\n", m_flags & e_bulletFlag);
        b2Log("  bd.active = bool(%d);\n", m_flags & e_activeFlag);
        b2Log("  bd.gravityScale = %.15lef;\n", m_gravityScale);
        b2Log("  bodies[%d] = m_world->CreateBody(&bd);\n", m_islandIndex);
        b2Log("\n");
        for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
        {
                b2Log("  {\n");
                f->Dump(bodyIndex);
                b2Log("  }\n");
        }
        b2Log("}\n");
}