cocos2d-x物理引擎的实现

#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()) );         }     } }