Coco2d-x Framebuffer笔记

OpenGL Framebuffer

OpenGL中Framebuffer的特性：

1.Framebuffer由什么组成：color buffer，depth buffer，stencil buffer

2.The default framebuffer is created and configured when you create your window (GLFW does this for us). 

3.For a framebuffer to be complete the following requirements have to be satisfied:

• We have to attach at least one buffer (color, depth or stencil buffer).
• There should be at least one color attachment.
• All attachments should be complete as well (reserved memory).
• Each buffer should have the same number of samples.

4.两种attachment：texture attachment（可读写，一般用作color buffer）和renderbuffer attachment（可写，一般用作depth stencil buffer）

5.一般使用方法：用texture作为color attachment ，depth attachment 和stencil attachment 共同使用一个buffer（GL_DEPTH24_STENCIL8）作为一个DepthStencil attachment（GL_DEPTH_STENCIL_ATTACHMENT），并且使用renderbuffer object作为attachment。

OpenGL使用Framebuffer的流程：

1.Gen

GLuint fbo;glGenFramebuffers(1, &fbo);

2.Bind

glBindFramebuffer(GL_FRAMEBUFFER, fbo); 

3.Attachment

（1）Texture Color Attachment

GLuint texture;

glGenTextures(1, &texture);glBindTexture(GL_TEXTURE_2D, texture);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 800, 600, 0, GL_RGB,GL_UNSIGNED_BYTE, NULL);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture,0); 

（2）Texture DepthStencil Attachment

GLuint texture;glGenTextures(1, &texture);glBindTexture(GL_TEXTURE_2D, texture);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 800, 600, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexImage2D( GL_TEXTURE_2D, 0, GL_DEPTH24_STENCIL8,800, 600, 0, GL_DEPTH_STENCIL, GL_UNSIGNED_INT_24_8, NULL);glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_TEXTURE_2D, texture,0); 

（3）Renderbuffer Color Attachments

GLuint rbo;glGenRenderbuffers(1, &rbo);glBindRenderbuffer(GL_RENDERBUFFER, rbo); glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA4, 800, 600);glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, rbo); 

（4）Renderbuffer DepthStencil  Attachments

GLuint rbo;glGenRenderbuffers(1, &rbo);glBindRenderbuffer(GL_RENDERBUFFER, rbo); glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, 800, 600);glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, rbo);

4.check complete

if(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE)// log info output

5.Delete

glDeleteFramebuffers(1, &fbo); 

Coco2d-x Framebuffer

1.使用framebuffer需要的所有参数：

1）Framebuffer size：width，height（Pixels Unit）

2）Attachment：color buffer（texture or renderbuffer），depth stencil buffer（renderbuffer）

3）Clear value for glClear*(type value)：vec3 clearcolor, GLfloat cleardepth, int8 clearstencil

2.删减版framebuffer.h

class CC_DLL FrameBuffer : public Ref{public:    static FrameBuffer* create(uint8_t fid, unsigned int width, unsigned int height);        bool init(uint8_t fid, unsigned int width, unsigned int height);public:    //call glclear to clear frame buffer object : color, depth, stencil    void clearFBO();    void applyFBO();    void restoreFBO();    void setClearColor(const Color4F& color) { _clearColor = color;}    void setClearDepth(float depth) { _clearDepth = depth; }    void setClearStencil(int8_t stencil) { _clearStencil = stencil; }    // set _rt    void attachRenderTarget(RenderTargetBase* rt);// set _rtDepthStencil    void attachDepthStencilTarget(RenderTargetDepthStencil* rt);        bool isDefaultFBO() const { return _isDefault; }    unsigned int getWidth() const { return _width; }    unsigned int getHeight() const { return _height; }CC_CONSTRUCTOR_ACCESS:    FrameBuffer();    virtual ~FrameBuffer();// init _defaultFBO with GLView    bool initWithGLView(GLView* view);private:    //openGL content for FrameBuffer    GLuint _fbo;    GLuint _previousFBO;    //dirty flag for fbo binding, if true need apply new attachment    bool _fboBindingDirty;    //    uint8_t _fid;    //    Color4F _clearColor;    float   _clearDepth;    int8_t  _clearStencil;    int _width;    int _height;    RenderTargetBase* _rt;    RenderTargetDepthStencil* _rtDepthStencil;    bool _isDefault;public:    static FrameBuffer* getOrCreateDefaultFBO(GLView* glView);    static void applyDefaultFBO();    static void clearAllFBOs();private:    //static GLuint _defaultFBO;    static FrameBuffer* _defaultFBO;    static std::set<FrameBuffer*> _frameBuffers;};

3.FBO相关操作

1）Create FrameBuffer

FrameBuffer* FrameBuffer::create(uint8_t fid, unsigned int width, unsigned int height){    auto result = new (std::nothrow) FrameBuffer();    if(result && result->init(fid, width, height))    {        result->autorelease();        return result;    }    else    {        CC_SAFE_DELETE(result);        return nullptr;    }}FrameBuffer::FrameBuffer(): _clearColor(Color4F(0, 0, 0, 1)), _clearDepth(1.0), _clearStencil(0), _fbo(0), _previousFBO(0), _rt(nullptr), _rtDepthStencil(nullptr), _fboBindingDirty(true), _isDefault(false){    _frameBuffers.insert(this);}bool FrameBuffer::init(uint8_t fid, unsigned int width, unsigned int height){    _fid = fid;    _width = width;    _height = height;        GLint oldfbo;    glGetIntegerv(GL_FRAMEBUFFER_BINDING, &oldfbo);    glGenFramebuffers(1, &_fbo);    glBindFramebuffer(GL_FRAMEBUFFER, _fbo);    glBindFramebuffer(GL_FRAMEBUFFER, oldfbo);        return true;}

new FrameBuffer 和init()都没有create RenderTarget，仅仅gen了一个FBO id，所以需要根据使用需求自己生成RenderTarget，并attach到FBO

2）Create RenderTarget

RenderTarget包括：RenderTargetBase（Render Target基类），RenderTarget（colorbuffer attachment为Texture2D的RenderTarget），RenderTargetRenderBuffer（colorbuffer attachment为RenderBuffer的RenderTarget），RenderTargetDepthStencil（DepthStencil attachment为RenderBuffer的RenderTarget），FrameBuffer。

//--------------------------------------------------------------------//// RenderTarget////--------------------------------------------------------------------RenderTarget* RenderTarget::create(unsigned int width, unsigned int height, Texture2D::PixelFormat format/* = Texture2D::PixelFormat::RGBA8888*/){    auto result = new (std::nothrow) RenderTarget();    if(result && result->init(width, height,format))    {        result->autorelease();        return result;    }    else    {        CC_SAFE_DELETE(result);        return nullptr;    }}bool RenderTarget::init(unsigned int width, unsigned int height, Texture2D::PixelFormat format){    if(!RenderTargetBase::init(width, height))    {        return false;    }        _texture = new (std::nothrow) Texture2D();    if(nullptr == _texture) return false;    //TODO: FIX me, get the correct bit depth for pixelformat    auto dataLen = width * height * 4;    auto data = malloc(dataLen);    if( nullptr == data) return false;        memset(data, 0, dataLen);    if(_texture->initWithData(data, dataLen, format, width, height, Size(width, height)))    {        _texture->autorelease();        CC_SAFE_RETAIN(_texture);        free(data);    }    else    {        CC_SAFE_DELETE(_texture);        free(data);        return false;    }    return true;}//--------------------------------------------------------------------//// RenderTarget////--------------------------------------------------------------------RenderTargetDepthStencil* RenderTargetDepthStencil::create(unsigned int width, unsigned int height){    auto result = new (std::nothrow) RenderTargetDepthStencil();        if(result && result->init(width, height))    {        result->autorelease();        return result;    }    else    {        CC_SAFE_DELETE(result);        return nullptr;    }}bool RenderTargetDepthStencil::init(unsigned int width, unsigned int height){    if(!RenderTargetBase::init(width, height)) return false;    GLint oldRenderBuffer(0);    glGetIntegerv(GL_RENDERBUFFER_BINDING, &oldRenderBuffer);        //generate depthStencil    glGenRenderbuffers(1, &_depthStencilBuffer);    glBindRenderbuffer(GL_RENDERBUFFER, _depthStencilBuffer);    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, width, height);    glBindRenderbuffer(GL_RENDERBUFFER, oldRenderBuffer);        return true;}//--------------------------------------------------------------------//// RenderTargetRenderBuffer////--------------------------------------------------------------------bool RenderTargetRenderBuffer::init(unsigned int width, unsigned int height){    if(!RenderTargetBase::init(width, height)) return false;    GLint oldRenderBuffer(0);    glGetIntegerv(GL_RENDERBUFFER_BINDING, &oldRenderBuffer);        //generate depthStencil    glGenRenderbuffers(1, &_colorBuffer);    glBindRenderbuffer(GL_RENDERBUFFER, _colorBuffer);    //todo: this could have a param    glRenderbufferStorage(GL_RENDERBUFFER, _format, width, height);    glBindRenderbuffer(GL_RENDERBUFFER, oldRenderBuffer);        return true;}RenderTargetRenderBuffer* RenderTargetRenderBuffer::create(unsigned int width, unsigned int height){    auto result = new (std::nothrow) RenderTargetRenderBuffer();        if(result && result->init(width, height))    {        result->autorelease();        return result;    }    else    {        CC_SAFE_DELETE(result);        return nullptr;    }}

3）attach RenderTarget

Color Attachment

void FrameBuffer::attachRenderTarget(RenderTargetBase* rt){    if(isDefaultFBO())    {        CCLOG("Can not apply render target to default FBO");        return;    }    CC_ASSERT(rt);    if(rt->getWidth() != _width || rt->getHeight() != _height)    {        CCLOG("Error, attach a render target with different size, Skip.");        return;    }    CC_SAFE_RETAIN(rt);    CC_SAFE_RELEASE(_rt);    _rt = rt;    _fboBindingDirty = true;//因为更新_rt，下次applyFBO()需要重新attach color attachment}

DepthStencil Attachment

void FrameBuffer::attachDepthStencilTarget(RenderTargetDepthStencil* rt){    if(isDefaultFBO())    {        CCLOG("Can not apply depth stencil target to default FBO");        return;    }        if(nullptr != rt && (rt->getWidth() != _width || rt->getHeight() != _height))    {        CCLOG("Error, attach a render target Depth stencil with different size, Skip.");        return;    }    CC_SAFE_RETAIN(rt);    CC_SAFE_RELEASE(_rtDepthStencil);    _rtDepthStencil = rt;    _fboBindingDirty = true;//因为更新了_rtDepthStencil，下次applyFBO()需要重新attach depth stencil attachment}

4) applyFBO

void FrameBuffer::applyFBO(){    CHECK_GL_ERROR_DEBUG();    glGetIntegerv(GL_FRAMEBUFFER_BINDING, (GLint*)&_previousFBO);    glBindFramebuffer(GL_FRAMEBUFFER, _fbo);//    CCASSERT(_fbo==0 || _fbo != _previousFBO, "calling applyFBO without restoring the previous one");    CHECK_GL_ERROR_DEBUG();    if(_fboBindingDirty && !isDefaultFBO())    {        CHECK_GL_ERROR_DEBUG();        if(RenderTargetBase::Type::Texture2D == _rt->getType())            glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, _rt->getTexture()->getName(), 0);        else            glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _rt->getBuffer());        CHECK_GL_ERROR_DEBUG();        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, nullptr == _rtDepthStencil ? 0 : _rtDepthStencil->getBuffer());        CHECK_GL_ERROR_DEBUG();        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, nullptr == _rtDepthStencil ? 0 : _rtDepthStencil->getBuffer());        CHECK_GL_ERROR_DEBUG();        CCLOG("FBO is %d _fbo %d color, %d ds", _fbo, RenderTargetBase::Type::Texture2D == _rt->getType() ? _rt->getTexture()->getName() : _rt->getBuffer(), nullptr == _rtDepthStencil ? 0 : _rtDepthStencil->getBuffer());        _fboBindingDirty = false;    }    if(GL_FRAMEBUFFER_COMPLETE != glCheckFramebufferStatus(GL_FRAMEBUFFER))    {        CCLOG("FrameBuffer Status Error %d", (int)glCheckFramebufferStatus(GL_FRAMEBUFFER));    }    CHECK_GL_ERROR_DEBUG();}

在attach时没有进行_rt断言，所以需要注意记得attach

5）clearAllFBO

void FrameBuffer::clearAllFBOs(){    for (auto fbo : _frameBuffers)    {        fbo->clearFBO();    }}void FrameBuffer::clearFBO(){    applyFBO();    glClearColor(_clearColor.r, _clearColor.g, _clearColor.b, _clearColor.a);    glClearDepth(_clearDepth);    glClearStencil(_clearStencil);    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT|GL_STENCIL_BUFFER_BIT);    restoreFBO();}void FrameBuffer::restoreFBO(){    glBindFramebuffer(GL_FRAMEBUFFER, _previousFBO);}

4.Director中FBO使用流程

 1）mainloop

void DisplayLinkDirector::mainLoop(){    if (_purgeDirectorInNextLoop)//end()函数会把_purgeDirectorInNextLoop设置为true    {        _purgeDirectorInNextLoop = false;//把_purgeDirectorInNextLoop恢复为默认值        purgeDirector();//清除Director    }    else if (_restartDirectorInNextLoop)    {        _restartDirectorInNextLoop = false;        restartDirector();    }    else if (! _invalid)    {        drawScene();             // release the objects        PoolManager::getInstance()->getCurrentPool()->clear();    }}

2）drawScene

void Director::drawScene(){    // calculate "global" dt    calculateDeltaTime();        if (_openGLView)    {        _openGLView->pollEvents();    }    //tick before glClear: issue #533    if (! _paused)    {        _eventDispatcher->dispatchEvent(_eventBeforeUpdate);_scheduler->update(_deltaTime);        _eventDispatcher->dispatchEvent(_eventAfterUpdate);    }    _renderer->clear();    experimental::FrameBuffer::clearAllFBOs();    /* to avoid flickr, nextScene MUST be here: after tick and before draw.     * FIXME: Which bug is this one. It seems that it can't be reproduced with v0.9     */    if (_nextScene)    {        setNextScene();    }    pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);        if (_runningScene)    {#if (CC_USE_PHYSICS || (CC_USE_3D_PHYSICS && CC_ENABLE_BULLET_INTEGRATION) || CC_USE_NAVMESH)        _runningScene->stepPhysicsAndNavigation(_deltaTime);#endif        //clear draw stats        _renderer->clearDrawStats();                //render the scene        _openGLView->renderScene(_runningScene, _renderer);                _eventDispatcher->dispatchEvent(_eventAfterVisit);    }    // draw the notifications node    if (_notificationNode)    {        _notificationNode->visit(_renderer, Mat4::IDENTITY, 0);    }    if (_displayStats)    {        showStats();    }    _renderer->render();    _eventDispatcher->dispatchEvent(_eventAfterDraw);    popMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);    _totalFrames++;    // swap buffers    if (_openGLView)    {        _openGLView->swapBuffers();    }    if (_displayStats)    {        calculateMPF();    }}

3）clearAllFBO

void FrameBuffer::clearAllFBOs(){    for (auto fbo : _frameBuffers)    {        fbo->clearFBO();    }}void FrameBuffer::clearFBO(){    applyFBO();    glClearColor(_clearColor.r, _clearColor.g, _clearColor.b, _clearColor.a);    glClearDepth(_clearDepth);    glClearStencil(_clearStencil);    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT|GL_STENCIL_BUFFER_BIT);    restoreFBO();}void FrameBuffer::restoreFBO(){    glBindFramebuffer(GL_FRAMEBUFFER, _previousFBO);}

4）renderScene

void GLView::renderScene(Scene* scene, Renderer* renderer){    CCASSERT(scene, "Invalid Scene");    CCASSERT(renderer, "Invalid Renderer");    if (_vrImpl)    {        _vrImpl->render(scene, renderer);    }    else    {        scene->render(renderer, Mat4::IDENTITY, nullptr);    }}

5）scene->render

void Scene::render(Renderer* renderer, const Mat4& eyeTransform, const Mat4* eyeProjection){    auto director = Director::getInstance();    Camera* defaultCamera = nullptr;    const auto& transform = getNodeToParentTransform();    for (const auto& camera : getCameras())    {        if (!camera->isVisible())            continue;        Camera::_visitingCamera = camera;        if (Camera::_visitingCamera->getCameraFlag() == CameraFlag::DEFAULT)        {            defaultCamera = Camera::_visitingCamera;        }        // There are two ways to modify the "default camera" with the eye Transform:        // a) modify the "nodeToParentTransform" matrix        // b) modify the "additional transform" matrix        // both alternatives are correct, if the user manually modifies the camera with a camera->setPosition()        // then the "nodeToParent transform" will be lost.        // And it is important that the change is "permanent", because the matrix might be used for calculate        // culling and other stuff.        if (eyeProjection)            camera->setAdditionalProjection(*eyeProjection * camera->getProjectionMatrix().getInversed());        camera->setAdditionalTransform(eyeTransform.getInversed());        director->pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_PROJECTION);        director->loadMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_PROJECTION, Camera::_visitingCamera->getViewProjectionMatrix());// apply viewport        camera->apply();        //clear background with max depth        camera->clearBackground();        //visit the scene        visit(renderer, transform, 0);#if CC_USE_NAVMESH        if (_navMesh && _navMeshDebugCamera == camera)        {            _navMesh->debugDraw(renderer);        }#endif        renderer->render();        camera->restore();        director->popMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_PROJECTION);        // we shouldn't restore the transform matrix since it could be used        // from "update" or other parts of the game to calculate culling or something else.//        camera->setNodeToParentTransform(eyeCopy);    }#if CC_USE_3D_PHYSICS && CC_ENABLE_BULLET_INTEGRATION    if (_physics3DWorld && _physics3DWorld->isDebugDrawEnabled())    {        director->pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_PROJECTION);        director->loadMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_PROJECTION, _physics3dDebugCamera != nullptr ? _physics3dDebugCamera->getViewProjectionMatrix() : defaultCamera->getViewProjectionMatrix());        _physics3DWorld->debugDraw(renderer);        renderer->render();        director->popMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_PROJECTION);    }#endif    Camera::_visitingCamera = nullptr;//    experimental::FrameBuffer::applyDefaultFBO();}

6）camera->apply

void Camera::apply(){    applyFrameBufferObject();    applyViewport();}void Camera::applyFrameBufferObject(){    if(nullptr == _fbo)//如果没有设置_fbo说明使用的是默认FBO，不需要bindFBO    {        // inherit from context if it doesn't have a FBO        // don't call apply the default one//        experimental::FrameBuffer::applyDefaultFBO();    }    else    {        _fbo->applyFBO();    }}void Camera::applyViewport(){    glGetIntegerv(GL_VIEWPORT, _oldViewport);    if(nullptr == _fbo)    {        glViewport(getDefaultViewport()._left, getDefaultViewport()._bottom, getDefaultViewport()._width, getDefaultViewport()._height);    }    else    {        glViewport(_viewport._left * _fbo->getWidth(), _viewport._bottom * _fbo->getHeight(),                   _viewport._width * _fbo->getWidth(), _viewport._height * _fbo->getHeight());    }}