cocos2d-x实现亮片效果

参考学长的项目，记录一下刀光效果的实现。

bool KongJianLayer::init()
{
	//调用父类的初始化
    if ( !Layer::init() )
    {
        return false;
    }

    Vec2 origin=Director::getInstance()->getVisibleOrigin();
    Size visibleSize=Director::getInstance()->getVisibleSize();

    Sprite *title = Sprite::create("gameTitle2.png");	//初始化游戏标题
    ClippingNode *cliper=ClippingNode::create(title);
	Sprite* stencil = title;									//设置剪裁模板为自
	Sprite* spark = Sprite::create("titleBlend.png");//初始化亮片
	spark->setPosition(-title->getContentSize().width,0);						//设置亮片的位置
	BlendFunc cbl = {GL_DST_COLOR, GL_ONE};								//定义混合类型
	spark->setBlendFunc(cbl);									//设置亮片混合
	cliper->setAlphaThreshold(0.5f);								//设置剪裁的透明度为0.5
	cliper->setStencil(stencil);									//设置剪裁模板
	cliper->addChild(spark);									//添加亮片
	this->addChild(cliper,10);									//添加剪裁到布景中
	cliper->setPosition(Point(origin.x+visibleSize.width/2,origin.y+visibleSize.height-200));
	MoveTo* moveTo = MoveTo::create(1.5f,Point(title->getContentSize().width,0));<span style="white-space:pre">			</span>//移动动画
	Place* moveBack = Place::create(Point(-title->getContentSize().width,0));	<span style="white-space:pre">		</span>//瞬时回到某点
	Sequence* seq = Sequence::create(moveTo,moveBack,DelayTime::create(1.0f),nullptr);<span style="white-space:pre">		</span>//顺序动作
	RepeatForever* action = RepeatForever::create(seq);						//重复执行的动作
	spark->runAction(action);									//亮片执行动作a

    return true;
}

此处涉及到剪裁模板概念，以及OpenGL里边的混合模式，下面列出OpenGL中常用的混合模式以及概念。

常量	RGB混合因子	Alpha混合因子
GL_ZERO	(0,0,0)	0
GL_ONE	(1,1,1)	1
GL_SRC_COLOR	(Rs,Rs,Rs)	As
GL_ONE_MINUS_SRC_COLOR	(1,1,1)- (Rs,Rs,Rs)	1-As
GL_DST_COLOR	(Rd,Rd,Rd)	Ad
GL_ONE_MINUS_DST_COLOR	(1,1,1)- (Rd,Rd,Rd)	1-Ad
GL_SRC_ALPHA	(As,As,As)	As
GL_ONE_MINUS_SRC_ALPHA	(1,1,1)- (As,As,As)	1- As
GL_DST_ALPHA	(Ad,Ad,Ad)	Ad
GL_ONE_MINUS_DST_ALPHA	(1,1,1)- (Ad,Ad,Ad)	1-Ad
GL_SRC_ALPHA_SATURATE	(f,f,f):f=min(As,1-Ad)	1

注：s:源颜色。d:目标颜色。

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