cocos2dx打飞机项目笔记六：GameScene类和碰撞检测 boundingbox

GameScene类虽然是占用游戏最多时间的类，但是里面的东西不是很多，最重要的就是碰撞检测了，碰撞检测代码如下：

 void GameScene::detectionCrash()
 {

     CCArray* bulletsToDelete = CCArray::create();//创建一个CCArray，用以存放待删除的子弹，也就是此帧中被检测到碰撞的子弹 
     bulletsToDelete->retain();//必须调用retain，CCArray内部调用了autoRelease
     CCObject* bt,*et;

     CCArray* enemyToDelete = CCArray::create();//创建一个CCArray，用以存放待删除的敌机，也就是此子弹击中的敌机
     enemyToDelete->retain();//调用retain  

     CCRect rectHero = this->heroLayer->getHero()->boundingBox();
     float x = rectHero.origin.x + rectHero.size.width * 0.3;
     float y = rectHero.origin.y + rectHero.size.height * 0.4;
     float width = rectHero.size.width * 0.3;
     float height = rectHero.size.height * 0.6;
     CCRect rect_HeroForCrash = CCRectMake(x, y, width, height);

     //检测敌机和hero是否相撞
     CCARRAY_FOREACH(this->enemyLayer->m_enemys,et)//遍历所有敌机
     {
         //break;

         Enemy* enemy = (Enemy*)et;
         if (enemy->getLife() == )
         {
             break;
         }

     //    CCPoint rect1 = this->heroLayer->getHero()->getPosition();
         //boundingBox 获取的是相对于父节点的左下角为原点的一个rect，所以要比较两个精灵是否相交，他们的父节点的坐标原点和大小应该一样
         if(enemy->boundingBox().intersectsRect(rect_HeroForCrash))
         {

             this->heroLayer->setIsHeroLive(false);
             this->heroLayer->setHeroLifes(this->heroLayer->getHeroLifes() - );

             enemyLayer->stopTakeEnemy();
             enemyLayer->bomb(enemy);
             enemyLayer->removeAllEnmeys();

             SimpleAudioEngine::sharedEngine()->pauseBackgroundMusic();

             int tempHightScore = GameScene::getHightestScore();
             if (this->m_totalScore > tempHightScore)
             {
                 GameScene::saveHightestScore(this->m_totalScore);
             }

             char life[];
             sprintf(life, "%d", this->heroLayer->getHeroLifes());
             CCLabelTTF* lbLife = (CCLabelTTF*)this->getChildByTag(tagOfLife);
             lbLife->setString(life);

             this->heroLayer->heroBomb(0.1f);
             if (this->heroLayer->getHeroLifes() == )
             {

                 this->scheduleOnce(schedule_selector(GameScene::gameOverCallback), 2.0f);
             }
             else
             {
                 this->scheduleOnce(schedule_selector(GameScene::newLife), 2.0f);
             }

             return;
         }
     }

     //检测敌机和子弹是否相撞
     CCARRAY_FOREACH(this->heroLayer->getBullets()->m_bullets,bt)//遍历所有子弹
     {
         CCSprite* bullet = (CCSprite*)bt;

         CCARRAY_FOREACH(this->enemyLayer->m_enemys,et)//遍历所有敌机
         {
             Enemy* enemy3 = (Enemy*)et;

             if(enemy3->boundingBox().intersectsRect(bullet->boundingBox()))
             {

                 if (enemy3->getLife() > )
                 {
                     enemy3->loseLife();
                     bulletsToDelete->addObject(bullet);//把待删除子弹放入CCArray  
                 }
                 else if (enemy3->getLife() == )
                 {
                     enemy3->loseLife();
                     bulletsToDelete->addObject(bullet);//把待删除子弹放入CCArray  
                     enemyToDelete->addObject(enemy3);//把待删除敌机放入CCArray 

                     this->m_totalScore += enemy3->getScore();

                     char str1[];
                     sprintf(str1, "%d",(int)this->m_totalScore);

                     CCLabelTTF* label1 = (CCLabelTTF*)this->getChildByTag(tagOfScore);

                     label1->setString(str1);
                 }

             }
         }

     }

     CCARRAY_FOREACH(enemyToDelete,et)//遍历所有此帧中碰撞死亡的敌机，必须是死亡
     {
         CCSprite* enemy3 = (CCSprite*)et;
         this->enemyLayer->bomb(enemy3);//执行爆炸
     }
     enemyToDelete->release();//release

     CCARRAY_FOREACH(bulletsToDelete,bt)//遍历所有此帧中碰撞的子弹
     {
         CCSprite* bullet = (CCSprite*)bt;
         this->heroLayer->getBullets()->removeBullet(bullet);//执行移除
     }
     bulletsToDelete->release();//release
 }

还记得之前说过 boundingbox 方法是获取节点以父节点左下角为原点的一个矩形吧，该矩形的大小就是节点各种变形后的大小，矩形的左下角坐标就是节点变形后的左下角坐标

bullet是加到 ccspriteBatchNode 上的，ccspriteBatchNode是加到 BulletLayer上面的，ccspriteBatchNode和bulletLayer都是铺满屏幕的。所以子弹调用 boundingbox 获得的矩形是以屏幕左下角为原点的。敌机的原理也是如此。hero是直接加到 herolayer 上的，父节点同样是铺满屏幕的，所以他们的父节点的左下角的坐标都一样的，这就是通过 boundingbox 检测他们是否碰撞的前提。

有些纹理周围有比较大的空白地方，这就会造成两个节点看起来还没有接触就会发生碰撞，这就需要对碰撞进行更精确的判断，可以通过什么像素判断法之类的。我这里采取最简单的处理方法，就是通过节点的boundingbox获取到一个rect，然后对这个rect加工一下：

     CCRect rectHero = this->heroLayer->getHero()->boundingBox();
     float x = rectHero.origin.x + rectHero.size.width * 0.3;
     float y = rectHero.origin.y + rectHero.size.height * 0.4;
     float width = rectHero.size.width * 0.3;
     float height = rectHero.size.height * 0.6;
     CCRect rect_HeroForCrash = CCRectMake(x, y, width, height);

这样子可以获取节点 boundingbox 里面的某一部分来作为碰撞的检测部分