如何使用box2d做碰撞检测

cocos2dx3.0+vs2012编译通过。

主要是通过body->SetTransform来设置body的位置和角度，然后自己写个ContactListener来监听碰撞事件

源代码下载

#include "HelloWorldScene.h"
#include "VisibleRect.h"
#include "GLES-Render.h"
#include "cocos-ext.h"

USING_NS_CC;
USING_NS_CC_EXT;

#define PTM_RATIO 32

Scene* HelloWorld::createScene()
{
    // 'scene' is an autorelease object
    auto scene = Scene::create();

    // 'layer' is an autorelease object
    auto layer = HelloWorld::create();

    // add layer as a child to scene
    scene->addChild(layer);

    // return the scene
    return scene;
}

// on "init" you need to initialize your instance
bool HelloWorld::init()
{
    //////////////////////////////
    // 1. super init first
    if ( !Layer::init() )
    {
        return false;
    }
    setTouchEnabled( true );
    Size visibleSize = Director::getInstance()->getVisibleSize();
    Point origin = Director::getInstance()->getVisibleOrigin();

    /////////////////////////////
    // 2. add a menu item with "X" image, which is clicked to quit the program
    //    you may modify it.

    // add a "close" icon to exit the progress. it's an autorelease object
    auto closeItem = MenuItemImage::create(
                                           "CloseNormal.png",
                                           "CloseSelected.png",
                                           CC_CALLBACK_1(HelloWorld::menuCloseCallback, this));

    closeItem->setPosition(Point(origin.x + visibleSize.width - closeItem->getContentSize().width/ ,
                                origin.y + closeItem->getContentSize().height/));

    // create menu, it's an autorelease object
    auto menu = Menu::create(closeItem, NULL);
    menu->setPosition(Point::ZERO);
    this->addChild(menu, );

    /////////////////////////////
    // 3. add your codes below...

    // add a label shows "Hello World"
    // create and initialize a label

    auto label = LabelTTF::create("Hello World", "Arial", );

    // position the label on the center of the screen
    label->setPosition(Point(origin.x + visibleSize.width/,
                            origin.y + visibleSize.height - label->getContentSize().height));

    // add the label as a child to this layer
    this->addChild(label, );

    // add "HelloWorld" splash screen"
    auto sprite = Sprite::create("HelloWorld.png");

    // position the sprite on the center of the screen
    sprite->setPosition(Point(visibleSize.width/ + origin.x, visibleSize.height/ + origin.y));

    // add the sprite as a child to this layer
    //this->addChild(sprite, 0);

    initPhysics();

    Point p(,);
    b2BodyDef bodyDef;
    bodyDef.type = b2_dynamicBody;
    bodyDef.position.Set(p.x/PTM_RATIO, p.y/PTM_RATIO);

    body = world->CreateBody(&bodyDef);

    // Define another box shape for our dynamic body.
    b2PolygonShape dynamicBox;
    dynamicBox.SetAsBox(.5f, .5f);//These are mid points for our 1m box

    // Define the dynamic body fixture.
    b2FixtureDef fixtureDef;
    fixtureDef.shape = &dynamicBox;
    fixtureDef.density = 1.0f;
    fixtureDef.friction = 0.3f;
    body->CreateFixture(&fixtureDef);    

    scheduleUpdate();

    //UILayer* pUiLayer = UILayer::create();
    //addChild(pUiLayer);

    //Layout* pWidget = dynamic_cast<Layout*>(CCUIHELPER->createWidgetFromJsonFile("cocoStudio/DemoShop.ExportJson"));
    //pUiLayer->addWidget(pWidget);

    return true;
}

void HelloWorld::menuCloseCallback(Object* pSender)
{
    Director::getInstance()->end();

#if (CC_TARGET_PLATFORM == CC_PLATFORM_IOS)
    exit();
#endif
}

void HelloWorld::initPhysics()
{
    b2Vec2 gravity;
    gravity.Set(0.0f, -10.0f);
    world = new b2World(gravity);

    // Do we want to let bodies sleep?
    world->SetAllowSleeping(true);

    world->SetContinuousPhysics(true);

     _debugDraw = new GLESDebugDraw( PTM_RATIO );
     world->SetDebugDraw(_debugDraw);

    uint32 flags = ;
    flags += b2Draw::e_shapeBit;
            flags += b2Draw::e_jointBit;
            flags += b2Draw::e_aabbBit;
           flags += b2Draw::e_pairBit;
            flags += b2Draw::e_centerOfMassBit;
    _debugDraw->SetFlags(flags);

    // Define the ground body.
    b2BodyDef groundBodyDef;
    groundBodyDef.position.Set(, ); // bottom-left corner

    // Call the body factory which allocates memory for the ground body
    // from a pool and creates the ground box shape (also from a pool).
    // The body is also added to the world.
    b2Body* groundBody = world->CreateBody(&groundBodyDef);

    // Define the ground box shape.
    b2EdgeShape groundBox;

    // bottom
    groundBox.Set(b2Vec2(VisibleRect::leftBottom().x/PTM_RATIO,VisibleRect::leftBottom().y/PTM_RATIO), b2Vec2(VisibleRect::rightBottom().x/PTM_RATIO,VisibleRect::rightBottom().y/PTM_RATIO));
    groundBody->CreateFixture(&groundBox,);

    // top
    groundBox.Set(b2Vec2(VisibleRect::leftTop().x/PTM_RATIO,VisibleRect::leftTop().y/PTM_RATIO), b2Vec2(VisibleRect::rightTop().x/PTM_RATIO,VisibleRect::rightTop().y/PTM_RATIO));
    groundBody->CreateFixture(&groundBox,);

    // left
    groundBox.Set(b2Vec2(VisibleRect::leftTop().x/PTM_RATIO,VisibleRect::leftTop().y/PTM_RATIO), b2Vec2(VisibleRect::leftBottom().x/PTM_RATIO,VisibleRect::leftBottom().y/PTM_RATIO));
    groundBody->CreateFixture(&groundBox,);

    // right
    groundBox.Set(b2Vec2(VisibleRect::rightBottom().x/PTM_RATIO,VisibleRect::rightBottom().y/PTM_RATIO), b2Vec2(VisibleRect::rightTop().x/PTM_RATIO,VisibleRect::rightTop().y/PTM_RATIO));
    groundBody->CreateFixture(&groundBox,);

    class TestListener : public b2ContactListener
    {
        virtual void BeginContact(b2Contact* contact)
        {
            //contact->GetFixtureA();
            //contact->GetFixtureB();
        }
        virtual void EndContact(b2Contact* contact)
        {
            //contact->GetFixtureA();
            //contact->GetFixtureB();
        }
    };
    pListener = new TestListener(); //don't forget to delete it
    world->SetContactListener(pListener);

    //groundBody->SetTransform
}

void HelloWorld::draw()
{
    //
    // IMPORTANT:
    // This is only for debug purposes
    // It is recommend to disable it
    //
    CCLayer::draw();

    GL::enableVertexAttribs( cocos2d::GL::VERTEX_ATTRIB_FLAG_POSITION );

    kmGLPushMatrix();

    world->DrawDebugData();

    kmGLPopMatrix();

}

void HelloWorld::update(float dt)
{
    //It is recommended that a fixed time step is used with Box2D for stability
    //of the simulation, however, we are using a variable time step here.
    //You need to make an informed choice, the following URL is useful
    //http://gafferongames.com/game-physics/fix-your-timestep/

    int velocityIterations = ;
    int positionIterations = ;

    // Instruct the world to perform a single step of simulation. It is
    // generally best to keep the time step and iterations fixed.
    world->Step(dt, velocityIterations, positionIterations);
}

void HelloWorld::onTouchesEnded(const std::vector<Touch*>& touches, Event* event)
{
    //Add a new body/atlas sprite at the touched location

    for (auto& touch : touches)
    {
        if(!touch)
            break;

        auto location = touch->getLocation();
        body->SetTransform(b2Vec2(location.x/PTM_RATIO,location.y/PTM_RATIO),);
        body->SetAwake(true);//防止静止之后就再也不动了
        //addNewSpriteAtPosition( location );
    }

}