b2_fixture.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,
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// SOFTWARE.

#include "box2d/b2_fixture.h"
#include "box2d/b2_block_allocator.h"
#include "box2d/b2_broad_phase.h"
#include "box2d/b2_chain_shape.h"
#include "box2d/b2_circle_shape.h"
#include "box2d/b2_collision.h"
#include "box2d/b2_contact.h"
#include "box2d/b2_edge_shape.h"
#include "box2d/b2_polygon_shape.h"
#include "box2d/b2_world.h"

b2Fixture::b2Fixture()
{
        m_body = nullptr;
        m_next = nullptr;
        m_proxies = nullptr;
        m_proxyCount = 0;
        m_shape = nullptr;
        m_density = 0.0f;
}

void b2Fixture::Create(b2BlockAllocator* allocator, b2Body* body, const b2FixtureDef* def)
{
        m_userData = def->userData;
        m_friction = def->friction;
        m_restitution = def->restitution;
        m_restitutionThreshold = def->restitutionThreshold;

        m_body = body;
        m_next = nullptr;

        m_filter = def->filter;

        m_isSensor = def->isSensor;

        m_shape = def->shape->Clone(allocator);

        // Reserve proxy space
        int32 childCount = m_shape->GetChildCount();
        m_proxies = (b2FixtureProxy*)allocator->Allocate(childCount * sizeof(b2FixtureProxy));
        for (int32 i = 0; i < childCount; ++i)
        {
                m_proxies[i].fixture = nullptr;
                m_proxies[i].proxyId = b2BroadPhase::e_nullProxy;
        }
        m_proxyCount = 0;

        m_density = def->density;
}

void b2Fixture::Destroy(b2BlockAllocator* allocator)
{
        // The proxies must be destroyed before calling this.
        b2Assert(m_proxyCount == 0);

        // Free the proxy array.
        int32 childCount = m_shape->GetChildCount();
        allocator->Free(m_proxies, childCount * sizeof(b2FixtureProxy));
        m_proxies = nullptr;

        // Free the child shape.
        switch (m_shape->m_type)
        {
        case b2Shape::e_circle:
                {
                        b2CircleShape* s = (b2CircleShape*)m_shape;
                        s->~b2CircleShape();
                        allocator->Free(s, sizeof(b2CircleShape));
                }
                break;

        case b2Shape::e_edge:
                {
                        b2EdgeShape* s = (b2EdgeShape*)m_shape;
                        s->~b2EdgeShape();
                        allocator->Free(s, sizeof(b2EdgeShape));
                }
                break;

        case b2Shape::e_polygon:
                {
                        b2PolygonShape* s = (b2PolygonShape*)m_shape;
                        s->~b2PolygonShape();
                        allocator->Free(s, sizeof(b2PolygonShape));
                }
                break;

        case b2Shape::e_chain:
                {
                        b2ChainShape* s = (b2ChainShape*)m_shape;
                        s->~b2ChainShape();
                        allocator->Free(s, sizeof(b2ChainShape));
                }
                break;

        default:
                b2Assert(false);
                break;
        }

        m_shape = nullptr;
}

void b2Fixture::CreateProxies(b2BroadPhase* broadPhase, const b2Transform& xf)
{
        b2Assert(m_proxyCount == 0);

        // Create proxies in the broad-phase.
        m_proxyCount = m_shape->GetChildCount();

        for (int32 i = 0; i < m_proxyCount; ++i)
        {
                b2FixtureProxy* proxy = m_proxies + i;
                m_shape->ComputeAABB(&proxy->aabb, xf, i);
                proxy->proxyId = broadPhase->CreateProxy(proxy->aabb, proxy);
                proxy->fixture = this;
                proxy->childIndex = i;
        }
}

void b2Fixture::DestroyProxies(b2BroadPhase* broadPhase)
{
        // Destroy proxies in the broad-phase.
        for (int32 i = 0; i < m_proxyCount; ++i)
        {
                b2FixtureProxy* proxy = m_proxies + i;
                broadPhase->DestroyProxy(proxy->proxyId);
                proxy->proxyId = b2BroadPhase::e_nullProxy;
        }

        m_proxyCount = 0;
}

void b2Fixture::Synchronize(b2BroadPhase* broadPhase, const b2Transform& transform1, const b2Transform& transform2)
{
        if (m_proxyCount == 0)
        {       
                return;
        }

        for (int32 i = 0; i < m_proxyCount; ++i)
        {
                b2FixtureProxy* proxy = m_proxies + i;

                // Compute an AABB that covers the swept shape (may miss some rotation effect).
                b2AABB aabb1, aabb2;
                m_shape->ComputeAABB(&aabb1, transform1, proxy->childIndex);
                m_shape->ComputeAABB(&aabb2, transform2, proxy->childIndex);
        
                proxy->aabb.Combine(aabb1, aabb2);

                b2Vec2 displacement = aabb2.GetCenter() - aabb1.GetCenter();

                broadPhase->MoveProxy(proxy->proxyId, proxy->aabb, displacement);
        }
}

void b2Fixture::SetFilterData(const b2Filter& filter)
{
        m_filter = filter;

        Refilter();
}

void b2Fixture::Refilter()
{
        if (m_body == nullptr)
        {
                return;
        }

        // Flag associated contacts for filtering.
        b2ContactEdge* edge = m_body->GetContactList();
        while (edge)
        {
                b2Contact* contact = edge->contact;
                b2Fixture* fixtureA = contact->GetFixtureA();
                b2Fixture* fixtureB = contact->GetFixtureB();
                if (fixtureA == this || fixtureB == this)
                {
                        contact->FlagForFiltering();
                }

                edge = edge->next;
        }

        b2World* world = m_body->GetWorld();

        if (world == nullptr)
        {
                return;
        }

        // Touch each proxy so that new pairs may be created
        b2BroadPhase* broadPhase = &world->m_contactManager.m_broadPhase;
        for (int32 i = 0; i < m_proxyCount; ++i)
        {
                broadPhase->TouchProxy(m_proxies[i].proxyId);
        }
}

void b2Fixture::SetSensor(bool sensor)
{
        if (sensor != m_isSensor)
        {
                m_body->SetAwake(true);
                m_isSensor = sensor;
        }
}

void b2Fixture::Dump(int32 bodyIndex)
{
        b2Dump("    b2FixtureDef fd;\n");
        b2Dump("    fd.friction = %.9g;\n", m_friction);
        b2Dump("    fd.restitution = %.9g;\n", m_restitution);
        b2Dump("    fd.restitutionThreshold = %.9g;\n", m_restitutionThreshold);
        b2Dump("    fd.density = %.9g;\n", m_density);
        b2Dump("    fd.isSensor = bool(%d);\n", m_isSensor);
        b2Dump("    fd.filter.categoryBits = uint16(%d);\n", m_filter.categoryBits);
        b2Dump("    fd.filter.maskBits = uint16(%d);\n", m_filter.maskBits);
        b2Dump("    fd.filter.groupIndex = int16(%d);\n", m_filter.groupIndex);

        switch (m_shape->m_type)
        {
        case b2Shape::e_circle:
                {
                        b2CircleShape* s = (b2CircleShape*)m_shape;
                        b2Dump("    b2CircleShape shape;\n");
                        b2Dump("    shape.m_radius = %.9g;\n", s->m_radius);
                        b2Dump("    shape.m_p.Set(%.9g, %.9g);\n", s->m_p.x, s->m_p.y);
                }
                break;

        case b2Shape::e_edge:
                {
                        b2EdgeShape* s = (b2EdgeShape*)m_shape;
                        b2Dump("    b2EdgeShape shape;\n");
                        b2Dump("    shape.m_radius = %.9g;\n", s->m_radius);
                        b2Dump("    shape.m_vertex0.Set(%.9g, %.9g);\n", s->m_vertex0.x, s->m_vertex0.y);
                        b2Dump("    shape.m_vertex1.Set(%.9g, %.9g);\n", s->m_vertex1.x, s->m_vertex1.y);
                        b2Dump("    shape.m_vertex2.Set(%.9g, %.9g);\n", s->m_vertex2.x, s->m_vertex2.y);
                        b2Dump("    shape.m_vertex3.Set(%.9g, %.9g);\n", s->m_vertex3.x, s->m_vertex3.y);
                        b2Dump("    shape.m_oneSided = bool(%d);\n", s->m_oneSided);
                }
                break;

        case b2Shape::e_polygon:
                {
                        b2PolygonShape* s = (b2PolygonShape*)m_shape;
                        b2Dump("    b2PolygonShape shape;\n");
                        b2Dump("    b2Vec2 vs[%d];\n", b2_maxPolygonVertices);
                        for (int32 i = 0; i < s->m_count; ++i)
                        {
                                b2Dump("    vs[%d].Set(%.9g, %.9g);\n", i, s->m_vertices[i].x, s->m_vertices[i].y);
                        }
                        b2Dump("    shape.Set(vs, %d);\n", s->m_count);
                }
                break;

        case b2Shape::e_chain:
                {
                        b2ChainShape* s = (b2ChainShape*)m_shape;
                        b2Dump("    b2ChainShape shape;\n");
                        b2Dump("    b2Vec2 vs[%d];\n", s->m_count);
                        for (int32 i = 0; i < s->m_count; ++i)
                        {
                                b2Dump("    vs[%d].Set(%.9g, %.9g);\n", i, s->m_vertices[i].x, s->m_vertices[i].y);
                        }
                        b2Dump("    shape.CreateChain(vs, %d);\n", s->m_count);
                        b2Dump("    shape.m_prevVertex.Set(%.9g, %.9g);\n", s->m_prevVertex.x, s->m_prevVertex.y);
                        b2Dump("    shape.m_nextVertex.Set(%.9g, %.9g);\n", s->m_nextVertex.x, s->m_nextVertex.y);
                }
                break;

        default:
                return;
        }

        b2Dump("\n");
        b2Dump("    fd.shape = &shape;\n");
        b2Dump("\n");
        b2Dump("    bodies[%d]->CreateFixture(&fd);\n", bodyIndex);
}