b2_body.cpp

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// 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.

#include "box2d/b2_body.h"
#include "box2d/b2_contact.h"
#include "box2d/b2_fixture.h"
#include "box2d/b2_joint.h"
#include "box2d/b2_world.h"

#include <new>

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 && bd->type != b2_staticBody)
        {
                m_flags |= e_awakeFlag;
        }
        if (bd->enabled)
        {
                m_flags |= e_enabledFlag;
        }

        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 = nullptr;
        m_contactList = nullptr;
        m_prev = nullptr;
        m_next = nullptr;

        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;

        m_mass = 0.0f;
        m_invMass = 0.0f;

        m_I = 0.0f;
        m_invI = 0.0f;

        m_userData = bd->userData;

        m_fixtureList = nullptr;
        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;
                m_flags &= ~e_awakeFlag;
                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 = nullptr;

        // 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 nullptr;
        }

        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_enabledFlag)
        {
                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_newContacts = true;

        return fixture;
}

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

        return CreateFixture(&def);
}

void b2Body::DestroyFixture(b2Fixture* fixture)
{
        if (fixture == NULL)
        {
                return;
        }

        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 != nullptr)
        {
                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_enabledFlag)
        {
                b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;
                fixture->DestroyProxies(broadPhase);
        }

        fixture->m_body = nullptr;
        fixture->m_next = nullptr;
        fixture->Destroy(allocator);
        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;
        }

        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, float 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);
        }

        // Check for new contacts the next step
        m_world->m_newContacts = true;
}

void b2Body::SynchronizeFixtures()
{
        b2BroadPhase* broadPhase = &m_world->m_contactManager.m_broadPhase;

        if (m_flags & b2Body::e_awakeFlag)
        {
                b2Transform xf1;
                xf1.q.Set(m_sweep.a0);
                xf1.p = m_sweep.c0 - b2Mul(xf1.q, m_sweep.localCenter);

                for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
                {
                        f->Synchronize(broadPhase, xf1, m_xf);
                }
        }
        else
        {
                for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
                {
                        f->Synchronize(broadPhase, m_xf, m_xf);
                }
        }
}

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

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

        if (flag)
        {
                m_flags |= e_enabledFlag;

                // 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 at the beginning of the next
                m_world->m_newContacts = true;
        }
        else
        {
                m_flags &= ~e_enabledFlag;

                // 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 = nullptr;
        }
}

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;

        // %.9g is sufficient to save and load the same value using text
        // FLT_DECIMAL_DIG == 9

        b2Dump("{\n");
        b2Dump("  b2BodyDef bd;\n");
        b2Dump("  bd.type = b2BodyType(%d);\n", m_type);
        b2Dump("  bd.position.Set(%.9g, %.9g);\n", m_xf.p.x, m_xf.p.y);
        b2Dump("  bd.angle = %.9g;\n", m_sweep.a);
        b2Dump("  bd.linearVelocity.Set(%.9g, %.9g);\n", m_linearVelocity.x, m_linearVelocity.y);
        b2Dump("  bd.angularVelocity = %.9g;\n", m_angularVelocity);
        b2Dump("  bd.linearDamping = %.9g;\n", m_linearDamping);
        b2Dump("  bd.angularDamping = %.9g;\n", m_angularDamping);
        b2Dump("  bd.allowSleep = bool(%d);\n", m_flags & e_autoSleepFlag);
        b2Dump("  bd.awake = bool(%d);\n", m_flags & e_awakeFlag);
        b2Dump("  bd.fixedRotation = bool(%d);\n", m_flags & e_fixedRotationFlag);
        b2Dump("  bd.bullet = bool(%d);\n", m_flags & e_bulletFlag);
        b2Dump("  bd.enabled = bool(%d);\n", m_flags & e_enabledFlag);
        b2Dump("  bd.gravityScale = %.9g;\n", m_gravityScale);
        b2Dump("  bodies[%d] = m_world->CreateBody(&bd);\n", m_islandIndex);
        b2Dump("\n");
        for (b2Fixture* f = m_fixtureList; f; f = f->m_next)
        {
                b2Dump("  {\n");
                f->Dump(bodyIndex);
                b2Dump("  }\n");
        }
        b2Dump("}\n");
}