cocos2d-x渲染流程分析

来源：互联网发布：大数据最重要的职位编辑：程序博客网时间：2024/05/19 07:09

上层的渲染函数为 Director::drawScene() 。Renderer::render() 为真正的渲染，但是在Renderer::render() 之前，有_runningScene->visit，其中_runningScene继承与Node，Node是cocos2d-x的基本渲染单位。node::visit的作用在于把要渲染的东西塞入到渲染队列中，堆栈如下：

cpp-tests.exe!cocos2d::Renderer::addCommand(cocos2d::RenderCommand * command=0x05d80150, int renderQueue=0) Line 255C++

cpp-tests.exe!cocos2d::Renderer::addCommand(cocos2d::RenderCommand * command=0x05d80150) Line 248C++

cpp-tests.exe!cocos2d::Sprite::draw(cocos2d::Renderer * renderer=0x00370040, const cocos2d::Mat4 & transform={...}, unsigned int flags=0) Line 603C++

cpp-tests.exe!cocos2d::Node::visit(cocos2d::Renderer * renderer=0x00370040, const cocos2d::Mat4 & parentTransform={...}, unsigned int parentFlags=0) Line 1266C++

cpp-tests.exe!cocos2d::Node::visit(cocos2d::Renderer * renderer=0x00370040, const cocos2d::Mat4 & parentTransform={...}, unsigned int parentFlags=0) Line 1262C++

cpp-tests.exe!cocos2d::Director::drawScene() Line 290C++

其中关键函数:

void Renderer::addCommand(RenderCommand* command, int renderQueue)

{

CCASSERT(!_isRendering, "Cannot add command while rendering");

CCASSERT(renderQueue >=0, "Invalid render queue");

CCASSERT(command->getType() != RenderCommand::Type::UNKNOWN_COMMAND, "Invalid Command Type");

_renderGroups[renderQueue].push_back(command);

}

_renderGroups就是渲染队列。RenderCommand记录了渲染操作相关信息，到真正渲染的时候会用上。
下一步就是真正的渲染操作，堆栈如下：
cpp-tests.exe!DrawPrimitivesTest::onDraw(const cocos2d::Mat4 & transform={...}, unsigned int flags=0) Line 126C++

...
...

cpp-tests.exe!cocos2d::CustomCommand::execute() Line 51C++

cpp-tests.exe!cocos2d::Renderer::visitRenderQueue(const cocos2d::RenderQueue & queue={...}) Line 314C++

cpp-tests.exe!cocos2d::Renderer::render() Line 367C++

cpp-tests.exe!cocos2d::Director::drawScene() Line 306C++
看关键代码：
for (ssize_t index = 0; index < size; ++index)

{

auto command = queue[index];

auto commandType = command->getType();

    if(RenderCommand::Type::QUAD_COMMAND == commandType)
          {
              ...
                _batchedQuadCommands.push_back(cmd);//注意这里，连续的QUAD渲染是会合并的(在同材质的情况下)，知道下个渲染command不再是QUAD_COMMAND类型，才会被提交渲染
              ...
            }
        else if(RenderCommand::Type::GROUP_COMMAND == commandType)
            {
              ...
            }
            else if(RenderCommand::Type::CUSTOM_COMMAND == commandType) //自定义渲染操作

{
flush();

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

cmd->execute();//执行渲染，最终调到DrawPrimitivesTest::onDraw这个函数中
}
最后Director::drawScene()调用

// swap buffers

if (_openGLView)

{

_openGLView->swapBuffers();

}
至此一帧的渲染流程结束。

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