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");
}
