【麦可网】Cocos2d-X跨平台游戏开发学习笔记---第二十四课：Cocos2D-X物理引擎之Box2D1-7-优快云博客

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【麦可网】Cocos2d-X跨平台游戏开发---学习笔记

第二十四课：Cocos2D-X物理引擎之Box2D1-7

=======================================================================================================================================================================

课程目标：

- 学习Box2D

课程重点：

- BOX2D概念

- BOX2D常用操作

- 使用物理编辑器

考核目标：

- 能够使用Box2D常用操作

- 使用物理编辑器完成物理对象编辑

=======================================================================================================================================================================

一、启动BOX2D

1、选中你编译的工程，按Alt + Enter快捷键（或者右键，选Propreties），在弹出的菜单中选择C/C++ --> Preprocossor，将Preprocessor Definition下的CC_ENABLE_CHIPMUNK_INTEGRATION=1修改为CC_ENABLE_BOX2D_INTEGRATION=1。

2、查看Linker -->Input下的Aditional Dependencies里，有没有libBox2d.lib。如果没有，手动添加之。

3、libExtensions类库也对应修改1和2步骤

二、实例一：使用BOX2D

HelloBox2D.h
--------------------
#pragma once

#include "cocos2d.h"
#include "Box2D/Box2D.h"
USING_NS_CC;

class HelloBox2D : public cocos2d::CCLayer
{
private:
	CCTexture2D* m_pSpriteTexture;
	b2World* world;

public:
	HelloBox2D();
	~HelloBox2D();
	// Here's a difference. Method 'init' in cocos2d-x returns bool, instead of returning 'id' in cocos2d-iphone
	virtual bool init();  

	// there's no 'id' in cpp, so we recommend returning the class instance pointer
	static cocos2d::CCScene* scene();

	// a selector callback
	void menuCloseCallback(CCObject* pSender);

	// implement the "static node()" method manually
	CREATE_FUNC(HelloBox2D);

	virtual void ccTouchesEnded(CCSet *pTouches, CCEvent *pEvent);
	void initPhysics();
	void addNewSpriteAtPosition(CCPoint p);
	void updata(float dt);
};

HelloBox2D.cpp
--------------------
#include "HelloBox2D.h"
#include "cocos-ext.h"
using namespace cocos2d::extension;
USING_NS_CC;

enum{
	kTagParentNode = 1,
};
#define PTM_RATIO 32.0f

CCScene* HelloBox2D::scene()
{
	// 'scene' is an autorelease object
	CCScene *scene = CCScene::create();

	// 'layer' is an autorelease object
	HelloBox2D *layer = HelloBox2D::create();

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

	// return the scene
	return scene;
}

HelloBox2D::HelloBox2D():
m_pSpriteTexture(NULL),
world(NULL)
{

}
HelloBox2D::~HelloBox2D()
{
	CC_SAFE_DELETE(world);
}

// on "init" you need to initialize your instance
bool HelloBox2D::init()
{
	//
	// 1. super init first
	if ( !CCLayer::init() )
	{
		return false;
	}
	setTouchEnabled(true);
	setAccelerometerEnabled(true);

	this->initPhysics();

	CCSpriteBatchNode* blocks = CCSpriteBatchNode::create("blocks.png",100);
	m_pSpriteTexture = blocks->getTexture();
	addChild(blocks, 0, kTagParentNode);

	//scheduleUpdate();
	this->schedule(schedule_selector(HelloBox2D::updata));

	return true;
}


void HelloBox2D::menuCloseCallback(CCObject* pSender)
{
	
}

void HelloBox2D::ccTouchesEnded(CCSet *pTouches, CCEvent *pEvent)
{
	CCSetIterator it;
	CCTouch* touch;

	for (it=pTouches->begin(); it!=pTouches->end();it++)
	{
		touch = (CCTouch*)(*it);
		if (!touch) break;

		CCPoint location = touch->getLocation();

		addNewSpriteAtPosition( location );
	}
	
}

void HelloBox2D::initPhysics()
{
	b2Vec2 gravity; 
	gravity.Set(0.0f,-10.0f);
	world = new b2World(gravity);

	world->SetAllowSleeping(true);
	world->SetContinuousPhysics(true);

	//创建物理空间的范围
	b2BodyDef groundBodyDef;
	groundBodyDef.position.Set(0, 0);
	//创建刚体
	b2Body* groundBody = world->CreateBody(&groundBodyDef);

	//创建形状
	b2EdgeShape groundBox;

	//创建夹具
	//将形状绑定到刚体上
	//button
	groundBox.Set(b2Vec2(0,0), b2Vec2(480/PTM_RATIO, 0));
	groundBody->CreateFixture(&groundBox, 0);

	//top
	groundBox.Set(b2Vec2(0,320/PTM_RATIO), b2Vec2(480/PTM_RATIO, 320/PTM_RATIO));
	groundBody->CreateFixture(&groundBox, 0);

	//left
	groundBox.Set(b2Vec2(0,320/PTM_RATIO), b2Vec2(0, 0));
	groundBody->CreateFixture(&groundBox, 0);


	//right
	groundBox.Set(b2Vec2(480/PTM_RATIO,320/PTM_RATIO), b2Vec2(480/PTM_RATIO, 0));
	groundBody->CreateFixture(&groundBox, 0);
}

void HelloBox2D::addNewSpriteAtPosition(CCPoint p)
{
	//定义刚体
	b2BodyDef bodyDef;
	bodyDef.type = b2_dynamicBody;
	bodyDef.position.Set(p.x/PTM_RATIO, p.y/PTM_RATIO);
	b2Body *body = world->CreateBody(&bodyDef);

	//定义多边形
	b2PolygonShape dynamicBox;
	dynamicBox.SetAsBox(.5f, .5f);

	//定义夹具
	b2FixtureDef fixtureDef;
	fixtureDef.shape = &dynamicBox;		//形状
	fixtureDef.density = 1.0f;			//密度
	fixtureDef.friction = 0.3f;			//摩擦系数
	body->CreateFixture(&fixtureDef);

	CCNode* parent = this->getChildByTag(kTagParentNode);

	int idx = (CCRANDOM_0_1() < 0.5 ? 0 : 1);
	int idy = (CCRANDOM_0_1() < 0.5 ? 0 : 1);
	if (idx==0 && idy==0)
	{
		int a =100;
		body->SetUserData(&a);
	}
	
	CCPhysicsSprite* sprite = CCPhysicsSprite::createWithTexture(m_pSpriteTexture, CCRectMake(32*idx, 32*idy, 32, 32));
	parent->addChild(sprite);
	sprite->setB2Body(body);
	sprite->setPTMRatio(PTM_RATIO);
	//sprite->setPosition( ccp( p.x, p.y) );//添加上这句在快速创建物理精灵时会出错
}

void HelloBox2D::updata(float dt)
{
	int velocityIterations = 8;
	int positionIterations = 1;

	world->Step(dt, velocityIterations, positionIterations);

#if 0
	//遍历刚体
	for (b2Body* b=world->GetBodyList(); b; b=b->GetNext())
	{
		int* tmp = (int*)b->GetUserData();
		if (*tmp == 100)
		{
			//千万不要在这里直接删除b指向的body对象，缓存后在后面删除
			CCLOG("body is a");
		}
		
	}

	//遍历碰撞点
	for ( b2Contact* c=world->GetContactList(); c; c=c->GetNext() )
	{
		千万不要在这里直接删除c指向的碰撞点对象，缓存后在后面删除
	}
	
#endif	
}