cocos2d-x物理引擎的实现

 本次的cocos2d-x的版本号为2.1.3，废话不多说，直接上代码！！！！！

#ifndef __HELLOWORLD_SCENE_H__
#define __HELLOWORLD_SCENE_H__

#include "cocos2d.h"

#include "Box2D/Box2D.h"
using namespace cocos2d;

class HelloWorld : public cocos2d::CCLayer
{
public:

    virtual bool init();

    static cocos2d::CCScene* scene();

    CREATE_FUNC(HelloWorld);

     HelloWorld ();
      ~HelloWorld ();

      void tick(float time);

private:
    //世界
    b2World *m_world;

    //刚体
    b2Body *m_body;

    //篮球
    CCSprite *m_ball;
};

#endif  // __HELLOWORLD_SCENE_H__

 

#include "HelloWorldScene.h"

using namespace cocos2d;

#define PTM_RATIO 32.0 //像素到米的转换

 HelloWorld :: HelloWorld ()
 {
     m_world = NULL;
     m_body = NULL;
     m_ball = NULL;

 }

 HelloWorld::~HelloWorld()
 {
     delete m_world ;
     m_body = NULL;
     m_ball = NULL;
 }


CCScene* HelloWorld::scene()
{
    CCScene * scene = NULL;
    do
    {

        scene = CCScene::create();
        CC_BREAK_IF(! scene);

        HelloWorld *layer = HelloWorld::create();
        CC_BREAK_IF(! layer);

        scene->addChild(layer);
    } while (0);

    return scene;
}


bool HelloWorld::init()
{
    bool bRet = false;
    do
    {

        CC_BREAK_IF(! CCLayer::init());

        CCSize size = CCDirector::sharedDirector()->getWinSize();

        //篮球
        m_ball = CCSprite::create("Ball.png");
        CC_BREAK_IF(!m_ball);
        m_ball->setPosition(ccp(100,400));
        this->addChild(m_ball);

        //创建一个世界
        b2Vec2 gravity(0.0f,-10.0f);
        m_world = new b2World(gravity);

        /**  创建围绕整个屏幕的边缘 **/
        //刚体定义
        b2BodyDef groundBodyDef;
        groundBodyDef.position.Set(0,0);

        //世界根据刚体定义生成刚体
        b2Body *groundBody = m_world->CreateBody(&groundBodyDef);

        //生成形状
        b2EdgeShape groundBox;


        //关联定义
        b2FixtureDef boxShapeDef;
        boxShapeDef.shape = &groundBox;

        //设置形状属性 ---下边框
        groundBox.Set( b2Vec2(0.0f,0.0f),b2Vec2(size.width/PTM_RATIO,0) );
        //创建关联
        groundBody->CreateFixture(&boxShapeDef);

        //设置形状属性 ---左边框
        groundBox.Set( b2Vec2(0.0f,0.0f),b2Vec2(0,size.height/PTM_RATIO) );
        //创建关联
        groundBody->CreateFixture(&boxShapeDef);

        //设置形状属性 ---上边框
        groundBox.Set( b2Vec2(0.0f,size.height/PTM_RATIO),b2Vec2(0,size.height/PTM_RATIO) );
        //创建关联
        groundBody->CreateFixture(&boxShapeDef);

        //设置形状属性 --右边框
        groundBox.Set( b2Vec2(size.width/PTM_RATIO,size.height/PTM_RATIO),
                             b2Vec2(size.width/PTM_RATIO,0.0f) );
        //创建关联
        groundBody->CreateFixture(&boxShapeDef);

        //创建篮球刚体与形状
        b2BodyDef ballBodyDef;
        ballBodyDef.type =b2_dynamicBody;
        ballBodyDef.position.Set(100/PTM_RATIO,400/PTM_RATIO);
        //关联篮球精灵
        ballBodyDef.userData = m_ball;
        //创建篮球刚体
        m_body = m_world->CreateBody(&ballBodyDef);

        //生成形状
        b2CircleShape circle;
        circle.m_radius = 26.0/PTM_RATIO;

        //关联定义
        b2FixtureDef ballShapeDef;
        ballShapeDef.shape = &circle;

        //密度
        ballShapeDef.density = 1.0f;
        //摩擦力
        ballShapeDef.friction = 1.0f;
        //反弹系数
        ballShapeDef.restitution = 0.8f;
        m_body->CreateFixture(&ballShapeDef);

        this->schedule(schedule_selector(HelloWorld::tick),0.1f);

        bRet = true;
    } while (0);

    return bRet;
}

void HelloWorld::tick(float time)
{
    //世界步
    m_world->Step(time,10,10);

    //获取世界的里的刚体
    for ( b2Body *body = m_world->GetBodyList();body!=NULL;body=body->GetNext() )
    {
        //获取篮球精灵
        if (body->GetUserData())
        {
            //根据刚体的位置设置篮球精灵的位置
            CCSprite *ballSprite = (CCSprite*)body->GetUserData();
            ballSprite->setPosition( ccp(body->GetPosition().x*PTM_RATIO,
                                     body->GetPosition().y*PTM_RATIO) );

            ballSprite->setRotation( -1*CC_RADIANS_TO_DEGREES(body->GetAngle()) );
        }
    }
}

运行结果：

 

代码已经写得很清晰了，我们总结下，首先创建一个世界，世界通过刚体定义生成刚体，关联把形状连接起来，刚体通过关联定义生成关联！！下面附上篮球一个！！

由于本人是业余，代码难免有所披露，望大家斧正！！谢谢，本人QQ947491240恭候大家拍砖！！再次感谢！！