Cocos2d-x 抖动效果

在网上看到一个挺有意思的东西 -- 抖动效果。这个动作应该可以用在制作战争类游戏炸弹爆炸或者渲染游戏画面效果等。

这是一个简单的动作，其实如果自己实现的话也是不难的，想一下都知道：所谓抖动，那么就是不停地在一个范围内变换位置，最后还原到原来的位置。

而我所看到网上贴出来的代码其实也是这样实现的。

下面贴出抖动效果CCShake这个动作的源码（代码中已经注释的很清楚了）：

#ifndef __SHAKE_H__
#define __SHAKE_H__

#include "cocos2d.h"
USING_NS_CC;

class CCShake : public cocos2d::CCActionInterval
{
public:
	CCShake();

    //下面给出了两个创建该抖动动作实例的类方法：
    
    //①参数指定动作执行时间和抖动范围（x和y相同）
	// Create the action with a time and a strength (same in x and y)
	static CCShake *create(float d, float strength );
    
    //②参数指定动作执行时间和x，y抖动范围
	// Create the action with a time and strengths (different in x and y)
	static CCShake *createWithStrength(float d, float strength_x, float strength_y );
    
	bool initWithDuration(float d, float strength_x, float strength_y );

protected:

	void startWithTarget(cocos2d::CCNode *pTarget);
	void update(float time);
	void stop(void);

	CCPoint m_StartPosition;

	// Strength of the action
	float m_strength_x, m_strength_y;
};

#endif //__SHAKE_H__

#include "CCShake.h"
#include "cocos2d.h"
USING_NS_CC;

// not really useful, but I like clean default constructors
CCShake::CCShake() : m_strength_x(0), m_strength_y(0)
{
}

CCShake *CCShake::create( float d, float strength )
{
	// call other construction method with twice the same strength
	return createWithStrength( d, strength, strength );
}

CCShake *CCShake::createWithStrength(float duration, float strength_x, float strength_y)
{
	CCShake *pRet = new CCShake();

	if (pRet && pRet->initWithDuration(duration, strength_x, strength_y))
	{
		pRet->autorelease();
	}
	else
	{
		CC_SAFE_DELETE(pRet);
	}


	return pRet;
}

bool CCShake::initWithDuration(float duration, float strength_x, float strength_y)
{
	if (CCActionInterval::initWithDuration(duration))
	{
		m_strength_x = strength_x;
		m_strength_y = strength_y;

		return true;
	}

	return false;
}

// Helper function. I included it here so that you can compile the whole file
// it returns a random value between min and max included
static float fgRangeRand( float min, float max )
{
	float rnd = ((float)rand() / (float)RAND_MAX);
	return rnd * (max - min) + min;
}

void CCShake::update(float dt)
{
	float randx = fgRangeRand( -m_strength_x, m_strength_x ) * dt;
	float randy = fgRangeRand( -m_strength_y, m_strength_y ) * dt;

	// move the target to a shaked position
	m_pTarget->setPosition( ccpAdd(m_StartPosition, ccp( randx, randy)));
}

void CCShake::startWithTarget(CCNode *pTarget)
{
	CCActionInterval::startWithTarget( pTarget );

	// save the initial position
	m_StartPosition=pTarget->getPosition();
}

void CCShake::stop(void)
{
	// Action is done, reset clip position
	this->getTarget()->setPosition( m_StartPosition);

	CCActionInterval::stop();
}

用法也是很简单

CCShake* shake = CCShake::create(3, 15);
    pSprite->runAction(shake);

参考文章：http://blog.justbilt.com/772/