制作飞镖忍者(2) Cocos2d-x 3.0alpha0

时间:2023-02-08 15:38:11

  在第一篇《制作飞镖忍者(1)》基础上,增加旋转炮塔功能,原文《How To Make A Simple iPhone Game with Cocos2D 2.X Part 2》,在这里继续以Cocos2d-x进行实现。有关源码、资源等在文章下面给出了地址。

步骤如下:
1.使用上一篇的工程;
2.下载本游戏所需的资源,将资源放置"Resources"目录下:
制作飞镖忍者(2) Cocos2d-x 3.0alpha0
删除旧的资源player.pngprojectile.png
3.在HelloWorldScene.cpp文件,init函数,修改创建玩家精灵:

        _player = Sprite::create("player2.png");
onTouchesEnded 函数,修改创建子弹精灵:

    Sprite* projectile = Sprite::create("projectile2.png");
4.编译运行,可以看到炮塔发射出了子弹,但是有一点奇怪,射击的时候,炮塔并没有朝向那个方向,如下图所示:

制作飞镖忍者(2) Cocos2d-x 3.0alpha0
5.计算炮塔旋转的角度。看下面图:
制作飞镖忍者(2) Cocos2d-x 3.0alpha0
数学的知识就是,tan(angle) = 对边 / 邻边,利用反正切angle = arctan(对边 / 邻边),这时计算出的是弧度,用CC_RADIANS_TO_DEGREES宏转换成角度。另外在数学中,逆时针为正,在Cocos2D-x中,顺时针为正,就如下图所示:
制作飞镖忍者(2) Cocos2d-x 3.0alpha0
需要将最后计算出的角度乘以-1。在
onTouchesEnded函数里,添加如下代码在projectile精灵runAction之前:

    float angleRadians = atanf((float)offRealY / (float)offRealX);
    float angleDegrees = CC_RADIANS_TO_DEGREES(angleRadians);
    float cocosAngle = -1 * angleDegrees;
    _player->setRotation(cocosAngle);
7.编译运行,这时就可以看到炮塔旋转射击了。如下图所示:

制作飞镖忍者(2) Cocos2d-x 3.0alpha0

8.旋转再射击。炮塔的旋转是瞬间完成的,这不符合现实,需要让它有个动作移动炮塔的方向。在HelloWorldScene.h文件中,添加如下声明:

    Sprite* _nextProjectile;
在构造函数里面,添加如下:

    _player = NULL;
    _nextProjectile = NULL;
修改 onTouchesEnded 函数,并且添加finishShoot方法,代码如下:

void HelloWorld::onTouchesEnded(const std::vector<Touch *> &touches, cocos2d::Event *event)
{
    if (_nextProjectile != NULL) {
        return;
    }
    
    
    Touch* touch = touches.front();
    Point location = this->convertTouchToNodeSpace(touch);
    
    
    Size winSize = Director::getInstance()->getWinSize();
    
    _nextProjectile = Sprite::create("projectile2.png");
    _nextProjectile->retain();
    _nextProjectile->setScale(2);
    _nextProjectile->setPosition(Point(20, winSize.height / 2));
    
    Point offset = ccpSub(location, _nextProjectile->getPosition());
    
    if (offset.x <= 0) {
        return;
    }
    
   
    
    int realX = winSize.width + _nextProjectile->getContentSize().width / 2;
    float ratio = (float)offset.y / (float)offset.x;
    int realY = realX * ratio + _nextProjectile->getPosition().y;
    Point realDest = Point(realX, realY);
    
    int offRealX = realX - _nextProjectile->getPosition().x;
    int offRealY = realY - _nextProjectile->getPosition().y;
    float length = sqrtf(offRealX * offRealX + offRealY * offRealY);
    float velocity = 480 / 1;
    
    float realMoveDuration = length / velocity;
    
    float angleRadians = atanf((float)offRealY / (float)offRealX);
    float angleDegrees = CC_RADIANS_TO_DEGREES(angleRadians);
    float cocosAngle = -1 * angleDegrees;
    
    float rotateDegreesPerSecond = 180 / 0.5;
    float degreesDiff = _player->getRotation() - cocosAngle;
    float rotateDuration = fabs(degreesDiff / rotateDegreesPerSecond);

    RotateTo* rotate = RotateTo::create(rotateDuration, cocosAngle);
    CallFunc* callFc = CallFunc::create(std::bind(&HelloWorld::finishShoot, this));
    
    _player->runAction(Sequence::create(rotate,callFc, NULL));
    
    
    _nextProjectile->runAction(Sequence::create(MoveTo::create(realMoveDuration, realDest),
                                                CallFuncN::create(std::bind(&HelloWorld::spriteMoveFinished, this,_nextProjectile)), NULL));
    _nextProjectile->setTag(2);
    
    

}

void HelloWorld::finishShoot()
{
    this->addChild(_nextProjectile);
    _projectiles->addObject(_nextProjectile);
    _nextProjectile->release();
    _nextProjectile = NULL;
}
在函数开头检验_nextProjectile变量,如果非空表示炮塔正在旋转中。不把_nextProjectile立即加到场景中,等待旋转完毕再加入场景。炮塔旋转的速度,为半秒钟旋转半个圆,计算所旋转角度所需的时间。
9.编译运行,可以看到炮塔可以在旋转后进行射击了,如下图所示:
制作飞镖忍者(2) Cocos2d-x 3.0alpha0

参考资料:
1.How To Make A Simple iPhone Game with Cocos2D 2.X Part 2 http://www.raywenderlich.com/25791/rotating-turrets-how-to-make-a-simple-iphone-game-with-cocos2d-2-x-part-2
2.(译)如何使用cocos2d开发一个简单的iphone游戏:旋转炮塔。(第二部分) http://www.cnblogs.com/zilongshanren/archive/2011/03/28/1997820.html
非常感谢以上资料,本例子源代码附加资源 下载地址 http://pan.baidu.com/s/16Bp7h
如文章存在错误之处,欢迎指出,以便改正。欢迎大家留言讨论技术!