cocos2dx刮奖效果实现

刮奖效果其实挺简单的，需要用到RenderTexture来进行渲染，通过你所要渲染的图层，把该层的颜色进行设置混合就可以达到效果，具体看代码，我用的lua实现的。

    local winsize = cc.Director:sharedDirector():getWinSize();
    local dataSprite = cc.Sprite:create("Star.png")--要把这个图片刮出来
    dataSprite:setAnchorPoint(cc.p(0.5, 0.5));
    dataSprite:move(winsize.width / 2.0, winsize.height / 2.0);
    self:addChild(dataSprite)

    pEarse = cc.DrawNode:create()
    pEarse:drawDot(cc.p(0, 0), 5, cc.c4f(1, 0, 0, 1));
    pEarse:retain()

    pRTex = cc.RenderTexture:create(winsize.width, winsize.height);
    pRTex:setPosition(cc.p(winsize.width / 2, winsize.height / 2));
    --this:addChild(pRTex);
    pRTex:retain()

    local pBg = cc.Sprite:create("d1.png");--这个作为当“油漆层”
    pBg:setAnchorPoint(cc.p(0.5, 0.5));
    pBg:move(winsize.width / 2.0, winsize.height / 2.0);

    pRTex:begin();
    dataSprite:visit();
    pBg:visit();
    pRTex:endToLua();
    local layer=cc.Layer:create()
    self:addChild(layer, 1000)
    layer:addChild(pRTex);
    layer:setNodeTouch(handler(self, self.onTouchStart))

鼠标移动代码：

function shop.erasure(event)
    -- body
    print("erasure: ", event.name)
    --todo
    print("moved")
    local touchPoint = event.pos
    pEarse:setPosition(event.pos.x, event.pos.y);
    -- 设置混合模式
    local blendFunc = { GL_ONE, GL_ZERO };
    pEarse:setBlendFunc(blendFunc);
    -- 将橡皮擦的像素渲染到画布上，与原来的像素进行混合
    pRTex:begin();
    pEarse:visit();
    pRTex:endToLua();
    
end

C++代码：

void function()

{

	 //test code
	 auto aPanelSprite = Sprite::create("potentiometerTrack.png");
	 aPanelSprite->setPosition(Vec2(s.width / 2, s.height / 2));
	 this->addChild(aPanelSprite);

	 pEase = DrawNode::create();
	 pEase->retain();
	 pEase->drawDot(Point(0, 0), 4.0f, Color4F(255, 0, 0, 255));

	 pRender = RenderTexture::create(s.width, s.height);
	 pRender->retain();
	 pRender->setPosition(Vec2(s.width / 2, s.height / 2));
	 this->addChild(pRender); //渲染纹理层需加入该父节点层


	auto pBg = Sprite::create("potentiometerProgress.png"); //这个作为当“油漆层”
	pBg->setAnchorPoint(Point(0.5, 0.5));
	pBg->setPosition(Vec2(s.width / 2, s.height / 2));

	pRender->begin();
	aPanelSprite->visit();
	pBg->visit();
	pRender->end();

	auto listener = EventListenerTouchOneByOne::create();
	listener->setSwallowTouches(true);

	listener->onTouchBegan = CC_CALLBACK_2(SpriteEaseBezier::onTouchBegan, this);
	listener->onTouchMoved = CC_CALLBACK_2(SpriteEaseBezier::onTouchMoved, this);

	auto _eventDispatcher = CCDirector::getInstance()->getEventDispatcher();
	_eventDispatcher->addEventListenerWithFixedPriority(listener, -10);
}

bool SpriteEaseBezier::onTouchBegan(Touch *touch, Event *unused_event)
{
	CCLOG("SpriteEaseBezier::onTouchBegan");
	return true;
}

void SpriteEaseBezier::onTouchMoved(Touch *touch, Event *unused_event)
{
	auto touchPoint = touch->getLocation();
	pEase->setPosition(touchPoint.x, touchPoint.y);

	BlendFunc blendFunc = { GL_ONE, GL_ZERO };
	pEase->setBlendFunc(blendFunc);

	pRender->begin();
	pEase->visit();
	pRender->end();
	CCLOG("SpriteEaseBezier::onTouchMoved");
}

这下好了，两个版本的都有了。