［cocos2d－x学习笔记］［入门基础］Box-2d物理引擎的使用02制作一个简易的愤怒小鸟Demo

在地图层创建一个游戏中出现的树杈发射器如图

部分代码如下

//创建树杈
auto tree01=Sprite::create("leftshot.png");
this->addChild(tree01);
tree01->setPosition(Vec2(200,200));
tree01->setScale(4);
auto tree02=Sprite::create("rightshot.png");
tree02->setPosition(Vec2(200,200));
tree02->setScale(4);
this->addChild(tree02);

2.创建世界，初始化世界，定义地板绑定夹具（详情请看01）；

//创建地板
b2BodyDef groundDef;
groundDef.position.Set(.0f, 50/32.0f);
b2Body *groundbody=world->CreateBody(&groundDef);
//创建夹具定义刚体形状
b2PolygonShape groundShop;
groundShop.SetAsBox(visibleSize.width/32, 50/32);
//刚体绑定夹具
groundbody->CreateFixture(&groundShop,0);

3.添加敌人小猪

添加小猪的动态刚体并且绑定图层

void HelloWorld::addPigAtPosition(Vec2 p)
{
//刚体
b2BodyDef bodyDef;
bodyDef.type=b2_dynamicBody;//??
bodyDef.position.Set(p.x/32, p.y/32);
b2Body *body=world->CreateBody(&bodyDef);
b2PolygonShape dynamicBox;
b2CircleShape d;
d.m_radius=5;//??
dynamicBox.SetAsBox(50/32.0/2.0f, 50/32.0/2.0f);
b2FixtureDef fixtureDef;
fixtureDef.shape=&dynamicBox;
fixtureDef.density=1.0f;
fixtureDef.friction=3.0f;
fixtureDef.restitution=0.5;
body->CreateFixture(&fixtureDef);
//绑定图层
auto sprite = Sprite::create("pig_2.png");
sprite->setTag(10+pigIndex);
sprite->setScale(0.5);
this->addChild(sprite);
body->SetUserData(sprite);//将这个新的Body中绑定精灵Sprite
sprite->setPosition( Vec2( p.x, p.y) );
pigIndex++;

}

在场景中添加小猪

void HelloWorld::addObstacles()
{
pigIndex=0;
this->addPigAtPosition(Vec2(700,0));
this->addPigAtPosition(Vec2(700,32));
this->addPigAtPosition(Vec2(700,64));
this->addPigAtPosition(Vec2(700,96));
this->addPigAtPosition(Vec2(700,128));
this->addPigAtPosition(Vec2(700,160));
//    this->addPigAtPosition(Vec2(700,192));
//    this->addPigAtPosition(Vec2(700,224));
//    this->addPigAtPosition(Vec2(700,256));
//
this->addPigAtPosition(Vec2(750,0));
this->addPigAtPosition(Vec2(750,32));
this->addPigAtPosition(Vec2(750,64));
this->addPigAtPosition(Vec2(750,96));
this->addPigAtPosition(Vec2(750,128));
this->addPigAtPosition(Vec2(750,160));
//    this->addPigAtPosition(Vec2(750,192));
//    this->addPigAtPosition(Vec2(750,224));
//    this->addPigAtPosition(Vec2(750,256));

this->addPigAtPosition(Vec2(800,0));
this->addPigAtPosition(Vec2(800,32));
this->addPigAtPosition(Vec2(800,64));
this->addPigAtPosition(Vec2(800,96));
this->addPigAtPosition(Vec2(800,128));
this->addPigAtPosition(Vec2(800,160));
}

模拟世界的实现

this->scheduleUpdate();

void HelloWorld::update(float t){
world->Step(t, 8, 3);//模拟物理世界
//获取所有刚体的信息
for (b2Body* b=world->GetBodyList(); b; b=b->GetNext()) {
if (b->GetUserData()) {//如果当前的body绑定了精灵
Sprite * sp=(Sprite *)b->GetUserData();
sp->setPosition(b->GetPosition().x*32,
b->GetPosition().y*32);
sp->setRotation(-CC_RADIANS_TO_DEGREES(b->GetAngle()));
}
}
}

效果图：



4.添加愤怒的小鸟

点击屏幕在树杈中间出现一只小鸟。可以随着鼠标移动。

创建小鸟

void  HelloWorld::addNewSpriteAtPoint(Vec2 p){

auto sprite = Sprite::create("bird1.png");
sprite->setTag(110+birdIndex);
sprite->setPosition(Vec2(200,200));
this->addChild(sprite);
sprite->setPosition( Vec2( p.x, p.y) );
}

屏幕交互

//屏幕交互
auto listener=EventListenerTouchOneByOne::create();
listener->onTouchBegan=[&](Touch *t,Event *e){
//birdBody
addNewSpriteAtPoint(Vec2(200,200));
this->getChildByTag(110+birdIndex)->setPosition(200,200);
startx=t->getLocation().x;
starty=t->getLocation().y;
m_isFlying=false;
return true;
};
listener->onTouchMoved=[&](Touch *t,Event *e){
//        addNewSpriteAtPoint(t->getLocation());
this->getChildByTag(110+birdIndex)->setPosition(200+t->getLocation().x-startx,
200+t->getLocation().y-starty);

};
listener->onTouchEnded=[&](Touch *t,Event *e){
this->shootBirdAtPosition(t->getLocation());
birdIndex++;
m_isFlying=true;

};
Director::getInstance()->getEventDispatcher()->addEventListenerWithSceneGraphPriority(listener, this);
//添加小鸟

效果图


5.将小鸟的图层与动态刚体绑定，并射出，撞到小猪

void HelloWorld::shootBirdAtPosition(Vec2 p)
{ //Set up a 1m squared box in the physics world
b2BodyDef bodyDef;
bodyDef.type = b2_dynamicBody;//动态刚体
bodyDef.position.Set(p.x/32, p.y/32);
b2Body *body = world->CreateBody(&bodyDef);
this->birdBody=body;
// Define another box shape for our dynamic body.
b2PolygonShape dynamicBox;
dynamicBox.SetAsBox(50/32.0/2.0f, 50/32.0/2.0f);//These are mid points for our 1m box
// Define the dynamic body fixture.
b2FixtureDef fixtureDef;
fixtureDef.shape = &dynamicBox;
fixtureDef.density = 1.0f;
fixtureDef.friction = 0.3f;
fixtureDef.restitution=0.5;
body->CreateFixture(&fixtureDef);

body->SetUserData(this->getChildByTag(110+birdIndex));//将这个新的Body中绑定精灵Sprite
b2Vec2 force = b2Vec2((200-p.x)/3, (200-p.y)/3);
birdBody->ApplyLinearImpulse(force, birdBody->GetPosition(),true);

}