物理引擎：用来模拟一套物理事件的物理代码。
#ifndef __HELLOWORLD_SCENE_H__
#define __HELLOWORLD_SCENE_H__
#include "cocos2d.h"
#include <Box2D/Box2D.h>
#define RATIO 80.0f
class HelloWorld : public cocos2d::Layer,public b2ContactListener
{
private:
b2World *world;
b2Body *groundBody;
public:
static cocos2d::Scene* createScene();
virtual bool init();
void menuCloseCallback(cocos2d::Ref* pSender);
virtual void update(float dt);
virtual void BeginContact(b2Contact* contact);
void addRect(float x,float y,b2BodyType type);
void addGround();
CREATE_FUNC(HelloWorld);
};
#endif // __HELLOWORLD_SCENE_H__
#include "HelloWorldScene.h"
USING_NS_CC;
Scene* HelloWorld::createScene()
{
auto scene = Scene::create();
auto layer = HelloWorld::create();
scene->addChild(layer);
return scene;
}
bool HelloWorld::init()
{
if ( !Layer::init() )
{
return false;
}
Size visibleSize = Director::getInstance()->getVisibleSize();
Vec2 origin = Director::getInstance()->getVisibleOrigin();
//创建世界
world=new b2World(b2Vec2(0,-10));
world->SetContactListener(this);
addGround();
addRect(5,5,b2_dynamicBody);
//addRect(1,5,b2_kinematicBody);//漂浮物体，不受重力影响
scheduleUpdate();
return true;
}
void HelloWorld::update(float dt){
world->Step(dt,8,3);
Sprite *s;
for (b2Body *b=world->GetBodyList();b;b=b->GetNext()) {
//if (b->GetType()==b2_dynamicBody) {
//log("%f",b->GetPosition().y);
if (b->GetUserData()) {
s=(Sprite*)b->GetUserData();
s->setPosition(b->GetPosition().x*RATIO,b->GetPosition().y*RATIO);
}
//}
}
}
void HelloWorld::BeginContact(b2Contact *contact){
if (contact->GetFixtureA()->GetBody()==groundBody||contact->GetFixtureB()->GetBody()==groundBody) {
log("有物体落在了地板上");
}
}
void HelloWorld::addRect(float positionX,float positionY,b2BodyType type){
//config box2d
b2BodyDef def;
def.position=b2Vec2(positionX,positionY);
//def.linearVelocity=b2Vec2(1,0);
//def.linearVelocity=b2Vec2(0,10);
def.type=type;
groundBody=world->CreateBody(&def);
b2PolygonShape shape;
shape.SetAsBox(0.5,0.5);
b2FixtureDef fixtureDef;
fixtureDef.density=1;
fixtureDef.friction=0.3;
fixtureDef.shape=&shape;
groundBody->CreateFixture(&fixtureDef);
//config cocos shape
auto s=Sprite::create();
s->setTextureRect(Rect(0,0,0.5*2*RATIO,0.5*2*RATIO));
addChild(s);
//s->setPosition(Point(def.position.x*RATIO,def.position.y*RATIO));
groundBody->SetUserData(s);
}
void HelloWorld::addGround(){
b2BodyDef def;
def.position=b2Vec2(400/RATIO,0);
def.type=b2_staticBody;
b2Body *body=world->CreateBody(&def);
b2PolygonShape groundShape;
groundShape.SetAsBox(400/RATIO,0.5);
b2FixtureDef fixureDef;
fixureDef.density=1;
fixureDef.friction=0.3;
fixureDef.shape=&groundShape;
body->CreateFixture(&fixureDef);
}
void HelloWorld::menuCloseCallback(Ref* pSender)
{
Director::getInstance()->end();
#if (CC_TARGET_PLATFORM == CC_PLATFORM_IOS)
exit(0);
#endif
}