Cocos2dx源码赏析(2)之渲染

这篇,继续从源码的角度来跟踪下Cocos2dx引擎的渲染进度,以此来梳理下Cocos2dx引擎是什么将灵活等元素突显在屏幕上的。

从上一篇对Cocos2dx启动流程的梳理中可见,Cocos2dx借助通过各平台的进口启动发动机,并在循环中调用Director::mainLoop方法来保持引擎的各样逻辑:

void Director::mainLoop()
{
    if (_purgeDirectorInNextLoop)
    {
        _purgeDirectorInNextLoop = false;
        purgeDirector();
    }
    else if (_restartDirectorInNextLoop)
    {
        _restartDirectorInNextLoop = false;
        restartDirector();
    }
    else if (! _invalid)
    {
        drawScene();

        // release the objects
        PoolManager::getInstance()->getCurrentPool()->clear();
    }
}

void Director::end()
{
    _purgeDirectorInNextLoop = true;
}

void Director::restart()
{
    _restartDirectorInNextLoop = true;
}

void Director::stopAnimation()
{
    _invalid = true;
}

当调用了Director::end()方法时,_2018正版葡京赌侠诗,purgeDirectorInNextLoop变量才会被置为true,并进行了purgeDirector()方法:

void Director::purgeDirector()
{
    reset();

    CHECK_GL_ERROR_DEBUG();

    // OpenGL view
    if (_openGLView)
    {
        _openGLView->end();
        _openGLView = nullptr;
    }

    // delete Director
    release();
}

可以见到,那里举办了一些重置和清理工作。即在急需收尾游戏的时候,可以调用Director::end()方法,让引擎跳出主循环,执行关闭。

调用了Director::restart()方法时,_restartDirectorInNextLoop变量会被置为true,即会履行restartDirector()方法:

void Director::restartDirector()
{
    reset();

    // RenderState need to be reinitialized
    RenderState::initialize();

    // Texture cache need to be reinitialized
    initTextureCache();

    // Reschedule for action manager
    getScheduler()->scheduleUpdate(getActionManager(), Scheduler::PRIORITY_SYSTEM, false);

    // release the objects
    PoolManager::getInstance()->getCurrentPool()->clear();

    // Restart animation
    startAnimation();

    // Real restart in script level
#if CC_ENABLE_SCRIPT_BINDING
    ScriptEvent scriptEvent(kRestartGame, nullptr);
    ScriptEngineManager::getInstance()->getScriptEngine()->sendEvent(&scriptEvent);
#endif
}

可以看看,在restartDirector方法中,先进行了重置reset方法,然后又跟着把渲染状态、纹理缓存、定时器、内存管理、动画等又再次先河化了。以此来促成休闲游重启的方案。

_invalid变量默许是true,刚早先在Director::init中会被置为false,在调用Director::stopAnimation()时,会将_invalid置为true,此时不满意条件,即不会调用drawScene()绘制场景的点子,当然在调用Director::startAnimation()又会将_invalid置为false,因此可以知道,当_invalid置为true时,引擎在做空循环。

上边,才好不不难真正进入正题,即当_invalid为false时,会调用drawScene方法来绘制场景,设置定时器,动画,事件循环等一体系处理:

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();
    }
}

先是在drawScene方法中,会先调用calculateDelta提姆(Tim)e方法来计量每帧的岁月间隔_delta提姆(Tim)e,即每帧执行一多元逻辑操作所开支的时日。

接到里判断了_openGLView,该目标是用来将OpenGL绘制的情节突显在不可同日而语平台对应的视图上,那里不一致的平台有区其他是贯彻。而_openGLView的赋值是在调用了Director::setOpenGLView方法里展开的,而setOpenGLView方法的调用,大家是在AppDelegate::applicationDidFinishLaunching()方法中调用的。所以,这里_openGLView正常意况下是不会为空的。那么,也就会执行_openGLView->poll伊夫nts()方法,那一个点子是个空落成,只在一定的阳台才做相应的拍卖。一般会在该办法中,检查有没触发什么风云(键盘输入、鼠标移动等)。

再接着有个_paused的判断,而_paused为置为true,即不满意条件是在调用了Director::pause方法中设置的,那么不满意条件时,就不会执行那里的代码:

    if (! _paused)
    {
        _eventDispatcher->dispatchEvent(_eventBeforeUpdate);
        _scheduler->update(_deltaTime);
        _eventDispatcher->dispatchEvent(_eventAfterUpdate);
    }

也就是当调用了Director::pause的措施,然后进入主循环,可是不会响应相应的轩然大波调度和定时器的换代处理。

后续往下实施,如下代码:

_renderer->clear();
experimental::FrameBuffer::clearAllFBOs();

这里,紧倘诺在绘制前,执行相应的清理工作(例如:清除颜色缓冲区和纵深缓冲区,清除帧缓冲对象等)。

接下来,就执行那行代码了:

if (_nextScene)
{
    setNextScene();
}

追踪一下,可以找到,在调用了Director的replaceScene、pushScene或popScene等格局时,会给_nextScene赋值,那多少个办法的意义分别是:
replaceScene:将要执行的光景压入场景栈中,并替换当前的面貌,_nextScene指向要实践的场景。
pushScene:将要执行的现象压入场景栈中,并将_nextScene指向要实施的情景。
popScene:在场景栈中弹出近年来场所,并将_nextScene指向上一个的景观。

上述那七个点子都是在下一帧绘制生效。在setNextScene会执行一些情景的处境切换,并将下一个要履行的光景指定为当下运作的面貌。

持续,再就执行上面的代码:

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);
}

pushMatrix会将模型视图的矩阵压入相应的栈中。而相应的栈有存放模型视图矩阵的栈,投影矩阵的栈,纹理矩阵的栈。接下来,首要看renderScene方法的调用。

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);
    }
}

这里,_vrImpl是有关VR的落到实处,那里先不关切。然后,就调用到了scene的render方法:

void Scene::render(Renderer* renderer, const Mat4* eyeTransforms, const Mat4* eyeProjections, unsigned int multiViewCount)
{
    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.
        for (unsigned int i = 0; i < multiViewCount; ++i) {
            if (eyeProjections)
                camera->setAdditionalProjection(eyeProjections[i] * camera->getProjectionMatrix().getInversed());
            if (eyeTransforms)
                camera->setAdditionalTransform(eyeTransforms[i].getInversed());
            director->pushProjectionMatrix(i);
            director->loadProjectionMatrix(Camera::_visitingCamera->getViewProjectionMatrix(), i);
        }

        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();

        for (unsigned int i = 0; i < multiViewCount; ++i)
            director->popProjectionMatrix(i);

        // 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())
    {
        Camera *physics3dDebugCamera = _physics3dDebugCamera != nullptr ? _physics3dDebugCamera: defaultCamera;

        for (unsigned int i = 0; i < multiViewCount; ++i) {
            if (eyeProjections)
                physics3dDebugCamera->setAdditionalProjection(eyeProjections[i] * physics3dDebugCamera->getProjectionMatrix().getInversed());
            if (eyeTransforms)
                physics3dDebugCamera->setAdditionalTransform(eyeTransforms[i].getInversed());
            director->pushProjectionMatrix(i);
            director->loadProjectionMatrix(physics3dDebugCamera->getViewProjectionMatrix(), i);
        }

        physics3dDebugCamera->apply();
        physics3dDebugCamera->clearBackground();

        _physics3DWorld->debugDraw(renderer);
        renderer->render();

        physics3dDebugCamera->restore();

        for (unsigned int i = 0; i < multiViewCount; ++i)
            director->popProjectionMatrix(i);
    }
#endif

    Camera::_visitingCamera = nullptr;
//    experimental::FrameBuffer::applyDefaultFBO();
}

在那几个render方法中,主要关心七个章程的调用,即上面这两行代码:

visit(renderer, transform, 0);
renderer->render();

此间的visit会调用到父类Node节点相应的visit方法:

void Node::visit(Renderer* renderer, const Mat4 &parentTransform, uint32_t parentFlags)
{
    // quick return if not visible. children won't be drawn.
    if (!_visible)
    {
        return;
    }

    uint32_t flags = processParentFlags(parentTransform, parentFlags);

    // IMPORTANT:
    // To ease the migration to v3.0, we still support the Mat4 stack,
    // but it is deprecated and your code should not rely on it
    _director->pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);
    _director->loadMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW, _modelViewTransform);

    bool visibleByCamera = isVisitableByVisitingCamera();

    int i = 0;

    if(!_children.empty())
    {
        sortAllChildren();
        // draw children zOrder < 0
        for(auto size = _children.size(); i < size; ++i)
        {
            auto node = _children.at(i);

            if (node && node->_localZOrder < 0)
                node->visit(renderer, _modelViewTransform, flags);
            else
                break;
        }
        // self draw
        if (visibleByCamera)
            this->draw(renderer, _modelViewTransform, flags);

        for(auto it=_children.cbegin()+i, itCend = _children.cend(); it != itCend; ++it)
            (*it)->visit(renderer, _modelViewTransform, flags);
    }
    else if (visibleByCamera)
    {
        this->draw(renderer, _modelViewTransform, flags);
    }

    _director->popMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);

    // FIX ME: Why need to set _orderOfArrival to 0??
    // Please refer to https://github.com/cocos2d/cocos2d-x/pull/6920
    // reset for next frame
    // _orderOfArrival = 0;
}

该措施首先会对当下节点下的子节点举办遍历并排序,那里遍历会遍历整个Node节点树,然后在调用自身的绘图方法draw。例如,精灵7-Up会调用天使自身的draw方法:

void Sprite::draw(Renderer *renderer, const Mat4 &transform, uint32_t flags)
{
    if (_texture == nullptr)
    {
        return;
    }

#if CC_USE_CULLING
    // Don't calculate the culling if the transform was not updated
    auto visitingCamera = Camera::getVisitingCamera();
    auto defaultCamera = Camera::getDefaultCamera();
    if (visitingCamera == defaultCamera) {
        _insideBounds = ((flags & FLAGS_TRANSFORM_DIRTY) || visitingCamera->isViewProjectionUpdated()) ? renderer->checkVisibility(transform, _contentSize) : _insideBounds;
    }
    else
    {
        // XXX: this always return true since
        _insideBounds = renderer->checkVisibility(transform, _contentSize);
    }

    if(_insideBounds)
#endif
    {
        _trianglesCommand.init(_globalZOrder,
                               _texture,
                               getGLProgramState(),
                               _blendFunc,
                               _polyInfo.triangles,
                               transform,
                               flags);

        renderer->addCommand(&_trianglesCommand);

#if CC_SPRITE_DEBUG_DRAW
        _debugDrawNode->clear();
        auto count = _polyInfo.triangles.indexCount/3;
        auto indices = _polyInfo.triangles.indices;
        auto verts = _polyInfo.triangles.verts;
        for(ssize_t i = 0; i < count; i++)
        {
            //draw 3 lines
            Vec3 from =verts[indices[i*3]].vertices;
            Vec3 to = verts[indices[i*3+1]].vertices;
            _debugDrawNode->drawLine(Vec2(from.x, from.y), Vec2(to.x,to.y), Color4F::WHITE);

            from =verts[indices[i*3+1]].vertices;
            to = verts[indices[i*3+2]].vertices;
            _debugDrawNode->drawLine(Vec2(from.x, from.y), Vec2(to.x,to.y), Color4F::WHITE);

            from =verts[indices[i*3+2]].vertices;
            to = verts[indices[i*3]].vertices;
            _debugDrawNode->drawLine(Vec2(from.x, from.y), Vec2(to.x,to.y), Color4F::WHITE);
        }
#endif //CC_SPRITE_DEBUG_DRAW
    }
}

在百事可乐的draw方法中,并不直接绘制,而是给renderer发送一个RenderCommand指令(那里是TrianglesCommand),renderer会将RenderCommand放入一个栈中,等Node节点元素都遍历达成,才实施RenderCommand指令。

坚守目的版本的发动机完成,就将绘制逻辑从Node节点树遍历中分离出来了。每一遍绘制就给renderer发送一个RenderCommand指令。

接下去看Renderer::render方法:

void Renderer::render()
{
    //Uncomment this once everything is rendered by new renderer
    //glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    //TODO: setup camera or MVP
    _isRendering = true;

    if (_glViewAssigned)
    {
        //Process render commands
        //1. Sort render commands based on ID
        for (auto &renderqueue : _renderGroups)
        {
            renderqueue.sort();
        }
        visitRenderQueue(_renderGroups[0]);
    }
    clean();
    _isRendering = false;
}

那里取出下标为0的渲染队列,然后,进一步通过visitRenderQueue来获取队列中的渲染指令Command:

void Renderer::visitRenderQueue(RenderQueue& queue)
{
    queue.saveRenderState();

    //
    //Process Global-Z < 0 Objects
    //
    const auto& zNegQueue = queue.getSubQueue(RenderQueue::QUEUE_GROUP::GLOBALZ_NEG);
    if (zNegQueue.size() > 0)
    {
        if(_isDepthTestFor2D)
        {
            glEnable(GL_DEPTH_TEST);
            glDepthMask(true);
            glEnable(GL_BLEND);
            RenderState::StateBlock::_defaultState->setDepthTest(true);
            RenderState::StateBlock::_defaultState->setDepthWrite(true);
            RenderState::StateBlock::_defaultState->setBlend(true);
        }
        else
        {
            glDisable(GL_DEPTH_TEST);
            glDepthMask(false);
            glEnable(GL_BLEND);
            RenderState::StateBlock::_defaultState->setDepthTest(false);
            RenderState::StateBlock::_defaultState->setDepthWrite(false);
            RenderState::StateBlock::_defaultState->setBlend(true);
        }
        glDisable(GL_CULL_FACE);
        RenderState::StateBlock::_defaultState->setCullFace(false);

        for (const auto& zNegNext : zNegQueue)
        {
            processRenderCommand(zNegNext);
        }
        flush();
    }

    //
    //Process Opaque Object
    //
    const auto& opaqueQueue = queue.getSubQueue(RenderQueue::QUEUE_GROUP::OPAQUE_3D);
    if (opaqueQueue.size() > 0)
    {
        //Clear depth to achieve layered rendering
        glEnable(GL_DEPTH_TEST);
        glDepthMask(true);
        glDisable(GL_BLEND);
        glEnable(GL_CULL_FACE);
        RenderState::StateBlock::_defaultState->setDepthTest(true);
        RenderState::StateBlock::_defaultState->setDepthWrite(true);
        RenderState::StateBlock::_defaultState->setBlend(false);
        RenderState::StateBlock::_defaultState->setCullFace(true);

        for (const auto& opaqueNext : opaqueQueue)
        {
            processRenderCommand(opaqueNext);
        }
        flush();
    }

    //
    //Process 3D Transparent object
    //
    const auto& transQueue = queue.getSubQueue(RenderQueue::QUEUE_GROUP::TRANSPARENT_3D);
    if (transQueue.size() > 0)
    {
        glEnable(GL_DEPTH_TEST);
        glDepthMask(false);
        glEnable(GL_BLEND);
        glEnable(GL_CULL_FACE);

        RenderState::StateBlock::_defaultState->setDepthTest(true);
        RenderState::StateBlock::_defaultState->setDepthWrite(false);
        RenderState::StateBlock::_defaultState->setBlend(true);
        RenderState::StateBlock::_defaultState->setCullFace(true);


        for (const auto& transNext : transQueue)
        {
            processRenderCommand(transNext);
        }
        flush();
    }

    //
    //Process Global-Z = 0 Queue
    //
    const auto& zZeroQueue = queue.getSubQueue(RenderQueue::QUEUE_GROUP::GLOBALZ_ZERO);
    if (zZeroQueue.size() > 0)
    {
        if(_isDepthTestFor2D)
        {
            glEnable(GL_DEPTH_TEST);
            glDepthMask(true);
            glEnable(GL_BLEND);

            RenderState::StateBlock::_defaultState->setDepthTest(true);
            RenderState::StateBlock::_defaultState->setDepthWrite(true);
            RenderState::StateBlock::_defaultState->setBlend(true);
        }
        else
        {
            glDisable(GL_DEPTH_TEST);
            glDepthMask(false);
            glEnable(GL_BLEND);

            RenderState::StateBlock::_defaultState->setDepthTest(false);
            RenderState::StateBlock::_defaultState->setDepthWrite(false);
            RenderState::StateBlock::_defaultState->setBlend(true);
        }
        glDisable(GL_CULL_FACE);
        RenderState::StateBlock::_defaultState->setCullFace(false);

        for (const auto& zZeroNext : zZeroQueue)
        {
            processRenderCommand(zZeroNext);
        }
        flush();
    }

    //
    //Process Global-Z > 0 Queue
    //
    const auto& zPosQueue = queue.getSubQueue(RenderQueue::QUEUE_GROUP::GLOBALZ_POS);
    if (zPosQueue.size() > 0)
    {
        if(_isDepthTestFor2D)
        {
            glEnable(GL_DEPTH_TEST);
            glDepthMask(true);
            glEnable(GL_BLEND);

            RenderState::StateBlock::_defaultState->setDepthTest(true);
            RenderState::StateBlock::_defaultState->setDepthWrite(true);
            RenderState::StateBlock::_defaultState->setBlend(true);
        }
        else
        {
            glDisable(GL_DEPTH_TEST);
            glDepthMask(false);
            glEnable(GL_BLEND);

            RenderState::StateBlock::_defaultState->setDepthTest(false);
            RenderState::StateBlock::_defaultState->setDepthWrite(false);
            RenderState::StateBlock::_defaultState->setBlend(true);
        }
        glDisable(GL_CULL_FACE);
        RenderState::StateBlock::_defaultState->setCullFace(false);

        for (const auto& zPosNext : zPosQueue)
        {
            processRenderCommand(zPosNext);
        }
        flush();
    }

    queue.restoreRenderState();
}

接下来,取出队列中的Command,并实施processRenderCommand方法:

void Renderer::processRenderCommand(RenderCommand* command)
{
    auto commandType = command->getType();
    if( RenderCommand::Type::TRIANGLES_COMMAND == commandType)
    {
        // flush other queues
        flush3D();

        auto cmd = static_cast<TrianglesCommand*>(command);

        // flush own queue when buffer is full
        if(_filledVertex + cmd->getVertexCount() > VBO_SIZE || _filledIndex + cmd->getIndexCount() > INDEX_VBO_SIZE)
        {
            CCASSERT(cmd->getVertexCount()>= 0 && cmd->getVertexCount() < VBO_SIZE, "VBO for vertex is not big enough, please break the data down or use customized render command");
            CCASSERT(cmd->getIndexCount()>= 0 && cmd->getIndexCount() < INDEX_VBO_SIZE, "VBO for index is not big enough, please break the data down or use customized render command");
            drawBatchedTriangles();
        }

        // queue it
        _queuedTriangleCommands.push_back(cmd);
        _filledIndex += cmd->getIndexCount();
        _filledVertex += cmd->getVertexCount();
    }
    else if (RenderCommand::Type::MESH_COMMAND == commandType)
    {
        flush2D();
        auto cmd = static_cast<MeshCommand*>(command);

        if (cmd->isSkipBatching() || _lastBatchedMeshCommand == nullptr || _lastBatchedMeshCommand->getMaterialID() != cmd->getMaterialID())
        {
            flush3D();

            CCGL_DEBUG_INSERT_EVENT_MARKER("RENDERER_MESH_COMMAND");

            if(cmd->isSkipBatching())
            {
                // XXX: execute() will call bind() and unbind()
                // but unbind() shouldn't be call if the next command is a MESH_COMMAND with Material.
                // Once most of cocos2d-x moves to Pass/StateBlock, only bind() should be used.
                cmd->execute();
            }
            else
            {
                cmd->preBatchDraw();
                cmd->batchDraw();
                _lastBatchedMeshCommand = cmd;
            }
        }
        else
        {
            CCGL_DEBUG_INSERT_EVENT_MARKER("RENDERER_MESH_COMMAND");
            cmd->batchDraw();
        }
    }
    else if(RenderCommand::Type::GROUP_COMMAND == commandType)
    {
        flush();
        int renderQueueID = ((GroupCommand*) command)->getRenderQueueID();
        CCGL_DEBUG_PUSH_GROUP_MARKER("RENDERER_GROUP_COMMAND");
        visitRenderQueue(_renderGroups[renderQueueID]);
        CCGL_DEBUG_POP_GROUP_MARKER();
    }
    else if(RenderCommand::Type::CUSTOM_COMMAND == commandType)
    {
        flush();
        auto cmd = static_cast<CustomCommand*>(command);
        CCGL_DEBUG_INSERT_EVENT_MARKER("RENDERER_CUSTOM_COMMAND");
        cmd->execute();
    }
    else if(RenderCommand::Type::BATCH_COMMAND == commandType)
    {
        flush();
        auto cmd = static_cast<BatchCommand*>(command);
        CCGL_DEBUG_INSERT_EVENT_MARKER("RENDERER_BATCH_COMMAND");
        cmd->execute();
    }
    else if(RenderCommand::Type::PRIMITIVE_COMMAND == commandType)
    {
        flush();
        auto cmd = static_cast<PrimitiveCommand*>(command);
        CCGL_DEBUG_INSERT_EVENT_MARKER("RENDERER_PRIMITIVE_COMMAND");
        cmd->execute();
    }
    else
    {
        CCLOGERROR("Unknown commands in renderQueue");
    }
}

可以看到在processRenderCommand中就是各连串型的Command的施行和呼应的处理了。而在七喜的绘图发的是TRIANGLES_COMMAND类型的下令,所以,直接看这几个drawBatchedTriangles:

void Renderer::drawBatchedTriangles()
{
    if(_queuedTriangleCommands.empty())
        return;

    CCGL_DEBUG_INSERT_EVENT_MARKER("RENDERER_BATCH_TRIANGLES");

    _filledVertex = 0;
    _filledIndex = 0;

    /************** 1: Setup up vertices/indices *************/

    _triBatchesToDraw[0].offset = 0;
    _triBatchesToDraw[0].indicesToDraw = 0;
    _triBatchesToDraw[0].cmd = nullptr;

    int batchesTotal = 0;
    int prevMaterialID = -1;
    bool firstCommand = true;

    for(const auto& cmd : _queuedTriangleCommands)
    {
        auto currentMaterialID = cmd->getMaterialID();
        const bool batchable = !cmd->isSkipBatching();

        fillVerticesAndIndices(cmd);

        // in the same batch ?
        if (batchable && (prevMaterialID == currentMaterialID || firstCommand))
        {
            CC_ASSERT(firstCommand || _triBatchesToDraw[batchesTotal].cmd->getMaterialID() == cmd->getMaterialID() && "argh... error in logic");
            _triBatchesToDraw[batchesTotal].indicesToDraw += cmd->getIndexCount();
            _triBatchesToDraw[batchesTotal].cmd = cmd;
        }
        else
        {
            // is this the first one?
            if (!firstCommand) {
                batchesTotal++;
                _triBatchesToDraw[batchesTotal].offset = _triBatchesToDraw[batchesTotal-1].offset + _triBatchesToDraw[batchesTotal-1].indicesToDraw;
            }

            _triBatchesToDraw[batchesTotal].cmd = cmd;
            _triBatchesToDraw[batchesTotal].indicesToDraw = (int) cmd->getIndexCount();

            // is this a single batch ? Prevent creating a batch group then
            if (!batchable)
                currentMaterialID = -1;
        }

        // capacity full ?
        if (batchesTotal + 1 >= _triBatchesToDrawCapacity) {
            _triBatchesToDrawCapacity *= 1.4;
            _triBatchesToDraw = (TriBatchToDraw*) realloc(_triBatchesToDraw, sizeof(_triBatchesToDraw[0]) * _triBatchesToDrawCapacity);
        }

        prevMaterialID = currentMaterialID;
        firstCommand = false;
    }
    batchesTotal++;

    /************** 2: Copy vertices/indices to GL objects *************/
    auto conf = Configuration::getInstance();
    if (conf->supportsShareableVAO() && conf->supportsMapBuffer())
    {
        //Bind VAO
        GL::bindVAO(_buffersVAO);
        //Set VBO data
        glBindBuffer(GL_ARRAY_BUFFER, _buffersVBO[0]);

        // option 1: subdata
//        glBufferSubData(GL_ARRAY_BUFFER, sizeof(_quads[0])*start, sizeof(_quads[0]) * n , &_quads[start] );

        // option 2: data
//        glBufferData(GL_ARRAY_BUFFER, sizeof(_verts[0]) * _filledVertex, _verts, GL_STATIC_DRAW);

        // option 3: orphaning + glMapBuffer
        // FIXME: in order to work as fast as possible, it must "and the exact same size and usage hints it had before."
        //  source: https://www.opengl.org/wiki/Buffer_Object_Streaming#Explicit_multiple_buffering
        // so most probably we won't have any benefit of using it
        glBufferData(GL_ARRAY_BUFFER, sizeof(_verts[0]) * _filledVertex, nullptr, GL_STATIC_DRAW);
        void *buf = glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
        memcpy(buf, _verts, sizeof(_verts[0]) * _filledVertex);
        glUnmapBuffer(GL_ARRAY_BUFFER);

        glBindBuffer(GL_ARRAY_BUFFER, 0);

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _buffersVBO[1]);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(_indices[0]) * _filledIndex, _indices, GL_STATIC_DRAW);
    }
    else
    {
        // Client Side Arrays
#define kQuadSize sizeof(_verts[0])
        glBindBuffer(GL_ARRAY_BUFFER, _buffersVBO[0]);

        glBufferData(GL_ARRAY_BUFFER, sizeof(_verts[0]) * _filledVertex , _verts, GL_DYNAMIC_DRAW);

        GL::enableVertexAttribs(GL::VERTEX_ATTRIB_FLAG_POS_COLOR_TEX);

        // vertices
        glVertexAttribPointer(GLProgram::VERTEX_ATTRIB_POSITION, 3, GL_FLOAT, GL_FALSE, kQuadSize, (GLvoid*) offsetof(V3F_C4B_T2F, vertices));

        // colors
        glVertexAttribPointer(GLProgram::VERTEX_ATTRIB_COLOR, 4, GL_UNSIGNED_BYTE, GL_TRUE, kQuadSize, (GLvoid*) offsetof(V3F_C4B_T2F, colors));

        // tex coords
        glVertexAttribPointer(GLProgram::VERTEX_ATTRIB_TEX_COORD, 2, GL_FLOAT, GL_FALSE, kQuadSize, (GLvoid*) offsetof(V3F_C4B_T2F, texCoords));

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _buffersVBO[1]);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(_indices[0]) * _filledIndex, _indices, GL_STATIC_DRAW);
    }

    /************** 3: Draw *************/
    for (int i=0; i<batchesTotal; ++i)
    {
        CC_ASSERT(_triBatchesToDraw[i].cmd && "Invalid batch");
        _triBatchesToDraw[i].cmd->useMaterial();
        glDrawElements(GL_TRIANGLES, (GLsizei) _triBatchesToDraw[i].indicesToDraw, GL_UNSIGNED_SHORT, (GLvoid*) (_triBatchesToDraw[i].offset*sizeof(_indices[0])) );
        _drawnBatches++;
        _drawnVertices += _triBatchesToDraw[i].indicesToDraw;
    }

    /************** 4: Cleanup *************/
    if (Configuration::getInstance()->supportsShareableVAO())
    {
        //Unbind VAO
        GL::bindVAO(0);
    }
    else
    {
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    }

    _queuedTriangleCommands.clear();
    _filledVertex = 0;
    _filledIndex = 0;
}

以此即是主要的绘图处理以及做相应的见面批次的处理。那里,就先写到那里,简单的讲重点是些OpenGL
api的调用,但是,作者对那些还并未深刻的明亮,就不“误人子弟”,做过多的解析了,前边等实践过再来更新此篇,解释得更详实些。由此,该篇只是勉强对渲染的代码执行流程作了简便的剖析,谈不上长远了解。但起码经过翻阅代码,可以领略相应的拍卖是怎么着完成的。

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作者:AlphaGL
出处:http://www.cnblogs.com/alphagl/
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