cocos2d Sprite混合达到水流动效果

使用Sprite混合setBlendFunc方式达到流动效果

void MainHomeLayer::updateWaterFall(float dt)
{
    static float offset = 0;
    if(NULL != _waterFall)
    {
        _waterFall->removeFromParentAndCleanup(true);
    }

    CCSprite* background = (CCSprite*)this->getChildByTag(eMainHomeLayer_Background);
    CCSprite * waterFall = CCSprite::create("img/mainHome/waterfall.png");
    CCTexture2DPixelFormat pixelFormat =  waterFall->getTexture()->getPixelFormat();

    if(kTexture2DPixelFormat_RGBA8888 == pixelFormat ||
       kTexture2DPixelFormat_RGB5A1 == pixelFormat ||
       kTexture2DPixelFormat_RGBA4444 == pixelFormat)
    {
        float scaleX = background->getScaleX();
        float scaleY = background->getScaleY();

        ///Render Texture Begin
        CCSize textrueSize = CCSizeMake(waterFall->getContentSize().width  * scaleX,waterFall->getContentSize().height * scaleY);
        CCRenderTexture* renderTexture = CCRenderTexture::create(textrueSize.width, textrueSize.height, kTexture2DPixelFormat_RGBA8888);
        renderTexture->begin();

        ccBlendFunc blendFunc1 = {GL_ONE,GL_ONE_MINUS_SRC_ALPHA};
        waterFall->setBlendFunc(blendFunc1);
        waterFall->setOpacity(30);
        waterFall->setPosition(CCPointMake(textrueSize.width * 0.5, textrueSize.height * 0.5));
        waterFall->setScaleX(scaleX);
        waterFall->setScaleY(scaleY);
        waterFall->visit();

        ccBlendFunc blendFunc = {GL_DST_ALPHA,GL_ONE_MINUS_DST_ALPHA};
        ccTexParams tp = {GL_LINEAR,GL_LINEAR,GL_REPEAT,GL_REPEAT};
        float PIXRIS_PRR_SECOND_WATER  =  (CCRANDOM_0_1() * 20 + 20) * scaleY;
        CCSprite * water = CCSprite::create("img/mainHome/Water02.jpg");
        water->setBlendFunc(blendFunc);
        water->setScaleX(scaleX);
        water->setScaleY(scaleY);
        water->getTexture()->setTexParameters(&tp);
        water->setTextureRect(CCRectMake(0, -offset, water->getContentSize().width, water->getContentSize().height));
        water->setPosition(CCPointMake(textrueSize.width * 0.5, textrueSize.height * 0.5));
        water->visit();

        renderTexture->end();
        ///Render Texture End

        this->setWaterFall(renderTexture->getSprite());
        this->getWaterFall()->removeFromParentAndCleanup(true);
        CCSize winSize = CCDirector::sharedDirector()->getWinSize();
        this->getWaterFall()->setPosition(CCPointMake(winSize.width * 0.87, winSize.height * 0.8));
        this->addChild(this->getWaterFall(),100);

        offset += PIXRIS_PRR_SECOND_WATER * dt;
    }
}