[cocos2dx]精灵遮罩

    CCSize size = CCDirector::sharedDirector()->getWinSize();
    //创建干净的画板
    CCRenderTexture *pRt = CCRenderTexture::create(size.width,size.height);
     CCAssert(pRt, "RenderTexture is invalid");
     addChild(pRt);
     pRt->setPosition(size.width/2,size.height/2);
    //创建遮罩图片
    CCSprite *pMask = CCSprite::create("CalendarMask.png");
    CCAssert(pMask,"mask sprite is invalid");
    pMask->setPosition(CCPointMake(pMask->getContentSize().width/2, pMask->getContentSize().height/2));
    //创建被遮罩图片
    CCSprite *pFlower = CCSprite::create("Calendar1.png");
    CCAssert(pFlower, "Flower sprite is invalid");
    pFlower->setPosition(CCPointMake(pFlower->getContentSize().width/2, pFlower->getContentSize().height/2));
    
    //先设置好 遮罩精灵 和 被遮罩精灵 在被渲染的时候采用什么样的颜色混合法则
    ccBlendFunc maskBlend = {GL_ONE, GL_ZERO};
    ccBlendFunc flowerBlend = {GL_DST_ALPHA, GL_ZERO};
    pMask->setBlendFunc(maskBlend);
    pFlower->setBlendFunc(flowerBlend);

    //开始把各种精灵渲染到画板上
    pRt->begin();
    //先渲染遮罩精灵。但是因为有个画板先被渲染。所以pMask是第二个被渲染的，即后被渲染。
    //所以在这一刻pMask是源颜色。调用pMask->visit()的时候吧精灵pMask上的每个像素的RGBA分量和1.0相乘。
    //所以遮罩图片被元模原样的渲染出来.
    pMask->visit();
    //再渲染被遮罩的精灵.在这一刻,之前先有pMask被渲染。所以pFlower后被渲染。pFlower就是源颜色。之前的pMask就是目标颜色。
     //调用pFlower->visit()的时候,精灵pFlower上的对应像素的RGBA分量和pMask上的对应像素的A分量相乘.因为前面设置了GL_DST_ALPHA。
    pFlower->visit();
    //停止渲染到画板
    pRt->end();

if (depthFormat_) 
{
   if( ! depthBuffer_ )
       glGenRenderbuffersOES(1, &depthBuffer_);
        
   glBindRenderbufferOES(GL_RENDERBUFFER_OES, depthBuffer_);
   if( multiSampling_ )
       glRenderbufferStorageMultisampleAPPLE(GL_RENDERBUFFER_OES, samplesToUse_, depthFormat_,backingWidth_, backingHeight_);
   else
       glRenderbufferStorageOES(GL_RENDERBUFFER_OES, depthFormat_, backingWidth_, backingHeight_);
   glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_DEPTH_ATTACHMENT_OES, GL_RENDERBUFFER_OES, depthBuffer_);
   // add by frankyang at 2012/5/8
   glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_STENCIL_ATTACHMENT_OES, GL_RENDERBUFFER_OES, depthBuffer_);
   // bind color buffer
   glBindRenderbufferOES(GL_RENDERBUFFER_OES, colorRenderbuffer_);
}

 // Add the view controller's view to the window and display.
window = [[UIWindow alloc] initWithFrame: [[UIScreen mainScreen] bounds]];
EAGLView *__glView = [EAGLView viewWithFrame: [window bounds]
　　pixelFormat: kEAGLColorFormatRGBA8
　　//depthFormat: GL_DEPTH_COMPONENT16_OES
　　depthFormat:GL_DEPTH24_STENCIL8_OES
　　preserveBackbuffer: NO
　　sharegroup:nil
　　multiSampling:NO
　　numberOfSamples:0];

glEnable(GL_STENCIL_TEST);
glStencilFunc(GL_ALWAYS, 0x1, 0x1);
glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);

void MaskBeginLayer::visit()
{
　　if (getChildrenCount() != 0) {
　　　　glEnable(GL_ALPHA_TEST);
　　　　glAlphaFunc(GL_GREATER, 0.0);

　　　　glEnable(GL_STENCIL_TEST);
　　　　glStencilFunc(GL_ALWAYS, 0x1, 0x1);
　　　　glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);

　　　　CCLayer::visit();

　　　　glDisable(GL_ALPHA_TEST);
　　　　glStencilFunc(GL_NOTEQUAL, 0x1, 0x1);
　　　　glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
　　}
}
void MaskEndLayer::visit()
{
　　glDisable(GL_STENCIL_TEST);

　　CCLayer::visit();
}