cocos2d::DrawNode* _eraser;

cocos2d::RenderTexture*_renderTexture;

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

Vec2 center=Vec2(visibleSize.width*0.5f+origin.x,visibleSize.height*0.5f+origin.y);

_eraser=DrawNode::create();

_eraser->drawDot(Vec2::ZERO,,Color4F(,,,));

_eraser->retain();

_renderTexture=RenderTexture::create((int)visibleSize.width,(int)visibleSize.height);

_renderTexture->setPosition(center);

addChild(_renderTexture);

Sprite*spirte=Sprite::create("title_bg.jpg");

spirte->setAnchorPoint(Vec2(0.5f,0.5f));

spirte->setPosition(center);

spirte->retain();

_renderTexture->begin();

spirte->visit();

_renderTexture->end();

Vec2 pos=touch->getLocation();//鼠标位置

_eraser->setPosition(pos);

BlendFunc blendFunc={GL_ONE,GL_ZERO};

_eraser->setBlendFunc(blendFunc);

_renderTexture->begin();

_eraser->visit();

_renderTexture->end();