From: http://cstriker1407.info/blog/cocos2dx-study-notes-custom-actions-realization-of-circular-motion/
最近在翻帖子的时候发现很多大牛都自己实现自定义动作，而不是通过各种动作进行组合，正好最近需要一个圆周运动的效果，就自己写了一个自定义的动作，这里备注下大致的实现思路。
备注：
该动作并未实际应用在游戏中，可能有bug。
数学复习：
截图来自【http://202.113.29.3/nankaisource/mathhands/Elementary%20mathematics/0103/010301/01030101.htm】
实现方式：
可参考这篇文章来实现：【http://www.jb51.cc/article/p-fdrufoeg-bcr.html】
作者自己也写了一个功能增强版的圆周运动，可以实现螺旋线式的圆周运动。代码比较简单，就不在细说了。
自己的实现：
CircleMoveAct.h：
#ifndef __CIRCLE_MOVE_ACT_H__ |
#define __CIRCLE_MOVE_ACT_H__
#include "cocos2d.h"
classCircleMoveAct :publiccocos2d::CCActionInterval
{
public
:
boolinitWithDuration(floatduration,constcocos2d::CCPoint& center,scaleDiff,255)!important; border:0px!important; white-space:normal; margin:0px!important; outline:0px!important; text-align:left!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-weight:normal!important; font-style:normal!important; min-height:inherit!important">angle);
virtualcocos2d::CCObject* copyWithZone(cocos2d::CCZone* pZone);
virtual
voidstartWithTarget(cocos2d::CCNode *pTarget);
update(
floattime);
static
CircleMoveAct* create(scale,61)!important; border:0px!important; white-space:normal; margin:0px!important; outline:0px!important; text-align:left!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-weight:bold!important; font-style:normal!important; min-height:inherit!important">protected:
m_duration;
cocos2d::CCPoint m_center;
m_scaleDiff;
m_currScale;
m_angle;
m_anglePreFrame;
int
m_frameCnts;
cocos2d::CCPoint m_initPos;
};
#endif // __CIRCLE_MOVE_ACT_H__
CircleMoveAct.cpp：
#include "CircleMoveAct.h"
USING_NS_CC;
CircleMoveAct* CircleMoveAct::create(
CCPoint& center,255)!important; border:0px!important; white-space:normal; margin:0px!important; outline:0px!important; text-align:left!important; float:none!important; vertical-align:baseline!important; position:static!important; left:auto!important; top:auto!important; right:auto!important; bottom:auto!important; height:auto!important; width:auto!important; line-height:1.1em!important; font-weight:normal!important; font-style:normal!important; min-height:inherit!important">angle)
CircleMoveAct *pRet =
newCircleMoveAct();
pRet->initWithDuration(duration,center,scale,angle);
pRet->autorelease();
return
pRet;
}
CircleMoveAct::initWithDuration(angle)
{
if
(CCActionInterval::initWithDuration(duration))
this
->m_duration = duration;
->m_center = center;
->m_scaleDiff = scaleDiff;
->m_currScale = 1.0f;
->m_angle = angle;
/************************************************************************/
/* 计算每次update调用时需要转动的弧度 */
->m_anglePreFrame = angle / duration * CCDirector::sharedDirector()->getAnimationInterval() / (180 / M_PI);
->m_frameCnts = 0;
return
true;
false
CCObject* CircleMoveAct::copyWithZone(CCZone *pZone)
CCZone* pNewZone = NULL;
CircleMoveAct* pCopy = NULL;
if
(pZone && pZone->m_pCopyObject)
pCopy = (CircleMoveAct*)(pZone->m_pCopyObject);
}
else
pCopy =
CircleMoveAct();
pZone = pNewZone =
CCZone(pCopy);
CCActionInterval::copyWithZone(pZone);
pCopy->initWithDuration(m_duration,m_center,m_scaleDiff,m_angle);
CC_SAFE_DELETE(pNewZone);
pCopy;
CircleMoveAct::startWithTarget(CCNode *pTarget)
CCActionInterval::startWithTarget(pTarget);
m_initPos = pTarget->getPosition();
CircleMoveAct::update(
)
m_frameCnts++;
m_currScale += m_scaleDiff;
CCPoint newPos = ccpRotateByAngle(m_initPos,m_frameCnts * m_anglePreFrame);
CCPoint diff = ccpSub(newPos,m_center);
newPos = diff * m_currScale + m_center;
m_pTarget->setPosition(newPos);
//debug
#if 0
CCDrawNode *node = CCDrawNode::create();
node->drawDot(newPos,3,ccc4f(128,128,128));
m_pTarget->getParent()->addChild(node);
#endif
}
