(1) 首先,这里以win32平台下为例子.win32下游戏的启动都是从win32目录下main文件开始的,即是游戏的入口函数,如下:
#include "main.h"
#include "AppDelegate.h"
#include "cocos2d.h" USING_NS_CC; int APIENTRY _tWinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPTSTR lpCmdLine,
int nCmdShow)
{
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine); // create the application instance
AppDelegate app;
// 启动游戏
return Application::getInstance()->run();
}
(1-1)这里可以看出,在入口函数中,首先创建了一个AppDelegate对象，AppDelegate继承 自CCApplication，在创建APPDelegate对象的时候就会隐式调用CCApplication构造函数，在这个构造函数里边会将AppDelegate的this指针传递给全局共享对象sm_pSharedApplication,如下:
Application::Application()
//初始化win32应用程序对象
: _instance(nullptr)
, _accelTable(nullptr)
{
_instance = GetModuleHandle(nullptr);
// 用于控制帧数的计数值
_animationInterval.QuadPart = ;
CC_ASSERT(! sm_pSharedApplication);
// 全局共享对象
sm_pSharedApplication = this;
}
(1-2) 接下来调用Application::getInstance()->run();启动游戏,如下:
int Application::run()
{
PVRFrameEnableControlWindow(false); // Main message loop:
LARGE_INTEGER nFreq;
LARGE_INTEGER nLast;
LARGE_INTEGER nNow; QueryPerformanceFrequency(&nFreq);
QueryPerformanceCounter(&nLast); // Initialize instance and cocos2d.
// 执行AppDeletegate重载的applicationDidFinishLaunching函数
if (!applicationDidFinishLaunching())
{
return ;
} auto director = Director::getInstance();
auto glview = director->getOpenGLView(); // Retain glview to avoid glview being released in the while loop
glview->retain(); while(!glview->windowShouldClose())
{
QueryPerformanceCounter(&nNow);
if (nNow.QuadPart - nLast.QuadPart > _animationInterval.QuadPart)
{
nLast.QuadPart = nNow.QuadPart;
// 主循环,每帧调用
director->mainLoop();
glview->pollEvents();
}
else
{
Sleep();
}
} // Director should still do a cleanup if the window was closed manually.
if (glview->isOpenGLReady())
{
// 结束,执行清理工作
director->end();
director->mainLoop();
director = nullptr;
}
glview->release();
return true;
}
(1-2-1) 我们进入到AppDelegate::applicationDidFinishLaunching(),看它究竟做了什么,我们以/cocos2d-x-3.2/templates/cpp-template-default/Classes/AppDelegate.cpp为例:
bool AppDelegate::applicationDidFinishLaunching() {
// initialize director
auto director = Director::getInstance();
auto glview = director->getOpenGLView();
if(!glview) {
// 创建glview对象, 这里采用默认的分辨率先创建出游戏窗口
glview = GLView::create("My Game");
// 这里设置了和OpenGL相关的一些信息
director->setOpenGLView(glview);
}
// turn on display FPS
director->setDisplayStats(true);
// set FPS. the default value is 1.0/60 if you don't call this
director->setAnimationInterval(1.0 / );
// create a scene. it's an autorelease object
// 创建场景
auto scene = HelloWorld::createScene();
// run 运行场景
director->runWithScene(scene);
return true;
}
(1-2-1-1) 可以看到applicationDidFinishLaunching函数里面设置了glview对象之后,就开始运行场景,可以进入GLView::create中看其究竟是如何创建GLView对象,同样,我们是win32下面看的, 所以找到cocos2d-x-3.2/cocos/platform/desktop/CCGLView.cpp文件:
GLView* GLView::create(const std::string& viewName)
{
auto ret = new GLView;
if(ret && ret->initWithRect(viewName, Rect(, , , ), )) {
ret->autorelease();
return ret;
} return nullptr;
}
从代码可以看到只是简单的new一个GLView对象,我们进入/cocos2d-x-3.2/cocos/platform/desktop/CCGLView.h看一下它究竟是个什么东西:
/****************************************************************************
Copyright (c) 2010-2012 cocos2d-x.org
Copyright (c) 2013-2014 Chukong Technologies Inc. http://www.cocos2d-x.org */ #ifndef __CC_EGLVIEW_DESKTOP_H__
#define __CC_EGLVIEW_DESKTOP_H__ #include "base/CCRef.h"
#include "platform/CCCommon.h"
#include "platform/CCGLViewProtocol.h"
#include "glfw3.h" NS_CC_BEGIN class CC_DLL GLView : public GLViewProtocol, public Ref
{
public:
static GLView* create(const std::string& viewName);
static GLView* createWithRect(const std::string& viewName, Rect size, float frameZoomFactor = 1.0f);
static GLView* createWithFullScreen(const std::string& viewName);
static GLView* createWithFullScreen(const std::string& viewName, const GLFWvidmode &videoMode, GLFWmonitor *monitor); /*
*frameZoomFactor for frame. This method is for debugging big resolution (e.g.new ipad) app on desktop.
*/ //void resize(int width, int height); float getFrameZoomFactor();
//void centerWindow(); virtual void setViewPortInPoints(float x , float y , float w , float h);
virtual void setScissorInPoints(float x , float y , float w , float h); bool windowShouldClose();
void pollEvents();
GLFWwindow* getWindow() const { return _mainWindow; } /* override functions */
virtual bool isOpenGLReady() override;
// 删除窗口，做窗口清理工作
virtual void end() override;
// 交换buffer
virtual void swapBuffers() override;
// 设置窗口大小
virtual void setFrameSize(float width, float height) override;
// 设置输入法状态
virtual void setIMEKeyboardState(bool bOpen) override; /*
* Set zoom factor for frame. This method is for debugging big resolution (e.g.new ipad) app on desktop.
*/
void setFrameZoomFactor(float zoomFactor); /** Retina support is disabled by default
* @note This method is only available on Mac.
*/
void enableRetina(bool enabled);
/** Check whether retina display is enabled. */
bool isRetinaEnabled() const { return _isRetinaEnabled; }; /** Get retina factor */
int getRetinaFactor() const { return _retinaFactor; } protected:
GLView();
virtual ~GLView(); bool initWithRect(const std::string& viewName, Rect rect, float frameZoomFactor);
bool initWithFullScreen(const std::string& viewName);
bool initWithFullscreen(const std::string& viewname, const GLFWvidmode &videoMode, GLFWmonitor *monitor); bool initGlew(); void updateFrameSize(); // GLFW callbacks
void onGLFWError(int errorID, const char* errorDesc);
void onGLFWMouseCallBack(GLFWwindow* window, int button, int action, int modify);
void onGLFWMouseMoveCallBack(GLFWwindow* window, double x, double y);
void onGLFWMouseScrollCallback(GLFWwindow* window, double x, double y);
void onGLFWKeyCallback(GLFWwindow* window, int key, int scancode, int action, int mods);
void onGLFWCharCallback(GLFWwindow* window, unsigned int character);
void onGLFWWindowPosCallback(GLFWwindow* windows, int x, int y);
void onGLFWframebuffersize(GLFWwindow* window, int w, int h);
void onGLFWWindowSizeFunCallback(GLFWwindow *window, int width, int height); bool _captured;
bool _supportTouch;
bool _isInRetinaMonitor;
bool _isRetinaEnabled;
int _retinaFactor; // Should be 1 or 2 float _frameZoomFactor; GLFWwindow* _mainWindow;
GLFWmonitor* _monitor; float _mouseX;
float _mouseY; friend class GLFWEventHandler; private:
CC_DISALLOW_COPY_AND_ASSIGN(GLView);
}; NS_CC_END // end of namespace cocos2d #endif // end of __CC_EGLVIEW_DESKTOP_H__
GLView继承自GLViewProtocol,我们也进入看一下:
/****************************************************************************
Copyright (c) 2010-2012 cocos2d-x.org
Copyright (c) 2013-2014 Chukong Technologies Inc. http://www.cocos2d-x.org *******************************************************/ #ifndef __CCGLVIEWPROTOCOL_H__
#define __CCGLVIEWPROTOCOL_H__ #include "base/ccTypes.h"
#include "base/CCEventTouch.h" #include <vector>
// 5种屏幕适配策略
enum class ResolutionPolicy
{
EXACT_FIT,
NO_BORDER,
SHOW_ALL,
FIXED_HEIGHT,
FIXED_WIDTH, UNKNOWN,
}; NS_CC_BEGIN class CC_DLL GLViewProtocol
{
public:
/**
* @js ctor
*/
GLViewProtocol();
/**
* @js NA
* @lua NA
*/
virtual ~GLViewProtocol(); /** Force destroying EGL view, subclass must implement this method. */
virtual void end() = ; /** Get whether opengl render system is ready, subclass must implement this method. */
virtual bool isOpenGLReady() = ; /** Exchanges the front and back buffers, subclass must implement this method. */
virtual void swapBuffers() = ; /** Open or close IME keyboard , subclass must implement this method. */
virtual void setIMEKeyboardState(bool open) = ; /**
* Polls input events. Subclass must implement methods if platform
* does not provide event callbacks.
*/
virtual void pollInputEvents(); /**
* Get the frame size of EGL view.
* In general, it returns the screen size since the EGL view is a fullscreen view.
*/
virtual const Size& getFrameSize() const; /**
* Set the frame size of EGL view.
*/
virtual void setFrameSize(float width, float height);
// 获取可见区域的原点和大小
virtual Size getVisibleSize() const;
virtual Vec2 getVisibleOrigin() const;
virtual Rect getVisibleRect() const; //设置设计的size，当需要适配多种设备时，可以用这个函数定义逻辑坐标，cocos2dx会自动将逻辑坐标转化成实际坐标,这样一样的代码可以适配各种设备分辨率
virtual void setDesignResolutionSize(float width, float height, ResolutionPolicy resolutionPolicy); /** Get design resolution size.
* Default resolution size is the same as 'getFrameSize'.
*/
virtual const Size& getDesignResolutionSize() const; /**
* Set opengl view port rectangle with points.
*/
virtual void setViewPortInPoints(float x , float y , float w , float h); /**
* Set Scissor rectangle with points.
*/
virtual void setScissorInPoints(float x , float y , float w , float h); /**
* Get whether GL_SCISSOR_TEST is enable
*/
virtual bool isScissorEnabled(); /**
* Get the current scissor rectangle
*/
virtual Rect getScissorRect() const; virtual void setViewName(const std::string& viewname);
const std::string& getViewName() const; /** Touch events are handled by default; if you want to customize your handlers, please override these functions: */
// 触摸处理函数，可以重载
virtual void handleTouchesBegin(int num, intptr_t ids[], float xs[], float ys[]);
virtual void handleTouchesMove(int num, intptr_t ids[], float xs[], float ys[]);
virtual void handleTouchesEnd(int num, intptr_t ids[], float xs[], float ys[]);
virtual void handleTouchesCancel(int num, intptr_t ids[], float xs[], float ys[]); /**
* Get the opengl view port rectangle.
*/
const Rect& getViewPortRect() const; /**
* Get scale factor of the horizontal direction.
*/
float getScaleX() const; /**
* Get scale factor of the vertical direction.
*/
float getScaleY() const; /** returns the current Resolution policy */
ResolutionPolicy getResolutionPolicy() const { return _resolutionPolicy; } protected:
void updateDesignResolutionSize(); void handleTouchesOfEndOrCancel(EventTouch::EventCode eventCode, int num, intptr_t ids[], float xs[], float ys[]); // real screen size
Size _screenSize;
// resolution size, it is the size appropriate for the app resources.
Size _designResolutionSize;
// the view port size
Rect _viewPortRect;
// the view name
std::string _viewName; float _scaleX;
float _scaleY;
ResolutionPolicy _resolutionPolicy;
}; // end of platform group
/// @} NS_CC_END #endif /* __CCGLVIEWPROTOCOL_H__ */
以看到CCEGLView和GLViewProtocol是显示窗口，负责窗口级别的功能管理和实现, 包括：坐标和缩放管理, 画图工具,按键事件;
(1-2-1-2) 创建glview对象之后,导演类Director就把glview设置进游戏,其中包括很多配置信息, 如设置屏幕大小适配相关的函数getDesignResolutionSize, 如下:
void Director::setOpenGLView(GLView *openGLView)
{
CCASSERT(openGLView, "opengl view should not be null"); if (_openGLView != openGLView)
{
// Configuration. Gather GPU info
Configuration *conf = Configuration::getInstance();
conf->gatherGPUInfo();
CCLOG("%s\n",conf->getInfo().c_str()); if(_openGLView)
_openGLView->release();
_openGLView = openGLView;
_openGLView->retain(); // set size 设置屏幕大小适配相关的函数
_winSizeInPoints = _openGLView->getDesignResolutionSize(); createStatsLabel(); if (_openGLView)
{
setGLDefaultValues();
}
// 完成初始化
_renderer->initGLView(); CHECK_GL_ERROR_DEBUG(); if (_eventDispatcher)
{
_eventDispatcher->setEnabled(true);
}
}
}
(1-2-1-2-1) 我们进入initGLView看看它都做了什么初始化工作,找到/cocos2d-x-3.2/cocos/renderer/CCRenderer.cpp:
void Renderer::initGLView()
{
#if CC_ENABLE_CACHE_TEXTURE_DATA
_cacheTextureListener = EventListenerCustom::create(EVENT_RENDERER_RECREATED, [this](EventCustom* event){
/** listen the event that renderer was recreated on Android/WP8 */
this->setupBuffer();
}); Director::getInstance()->getEventDispatcher()->addEventListenerWithFixedPriority(_cacheTextureListener, -);
#endif
// 填充索引缓冲
setupIndices(); setupBuffer(); _glViewAssigned = true;
}
(1-2-1-2-1-1) 进入setupIndices如下:
void Renderer::setupIndices()
{
for( int i=; i < VBO_SIZE; i++)
{
// 计算索引缓冲值
_indices[i*+] = (GLushort) (i*+);
_indices[i*+] = (GLushort) (i*+);
_indices[i*+] = (GLushort) (i*+);
_indices[i*+] = (GLushort) (i*+);
_indices[i*+] = (GLushort) (i*+);
_indices[i*+] = (GLushort) (i*+);
}
}
(1-2-1-2-1-2) 进入setupBuffer如下:
void Renderer::setupBuffer()
{
// 如果使用VAO
if(Configuration::getInstance()->supportsShareableVAO())
{
// 初始化VAO和VBO
setupVBOAndVAO();
}
else
{
// 初始化VBO
setupVBO();
}
}
(1-2-1-2-1-2-1) 进入setupVBOAndVAO和setupVBO, 开始调用OpenGL API进行顶点数据指定,具体意义参见基于Cocos2d-x学习OpenGL ES 2.0系列——编写自己的shader（2）:
void Renderer::setupVBOAndVAO()
{
glGenVertexArrays(, &_quadVAO);
GL::bindVAO(_quadVAO); glGenBuffers(, &_buffersVBO[]); glBindBuffer(GL_ARRAY_BUFFER, _buffersVBO[]);
glBufferData(GL_ARRAY_BUFFER, sizeof(_quads[]) * VBO_SIZE, _quads, GL_DYNAMIC_DRAW); // vertices
glEnableVertexAttribArray(GLProgram::VERTEX_ATTRIB_POSITION);
glVertexAttribPointer(GLProgram::VERTEX_ATTRIB_POSITION, , GL_FLOAT, GL_FALSE, sizeof(V3F_C4B_T2F), (GLvoid*) offsetof( V3F_C4B_T2F, vertices)); // colors
glEnableVertexAttribArray(GLProgram::VERTEX_ATTRIB_COLOR);
glVertexAttribPointer(GLProgram::VERTEX_ATTRIB_COLOR, , GL_UNSIGNED_BYTE, GL_TRUE, sizeof(V3F_C4B_T2F), (GLvoid*) offsetof( V3F_C4B_T2F, colors)); // tex coords
glEnableVertexAttribArray(GLProgram::VERTEX_ATTRIB_TEX_COORD);
glVertexAttribPointer(GLProgram::VERTEX_ATTRIB_TEX_COORD, , GL_FLOAT, GL_FALSE, sizeof(V3F_C4B_T2F), (GLvoid*) offsetof( V3F_C4B_T2F, texCoords)); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _buffersVBO[]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(_indices[]) * VBO_SIZE * , _indices, GL_STATIC_DRAW); // Must unbind the VAO before changing the element buffer.
GL::bindVAO();
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, );
glBindBuffer(GL_ARRAY_BUFFER, ); CHECK_GL_ERROR_DEBUG();
} void Renderer::setupVBO()
{
glGenBuffers(, &_buffersVBO[]); mapBuffers();
}
(1-2-2) 在applicationDidFinishLaunching里面创建场景之后,就调用director->mainLoop();开始游戏主循环了.我们进入mainLoop看它做了什么, win32下我们找到cocos2d-x-3.2/cocos/base/CCDirector.cpp:
void DisplayLinkDirector::mainLoop()
{
if (_purgeDirectorInNextLoop)
{
_purgeDirectorInNextLoop = false;
// 主循环结束,清除工作
purgeDirector();
}
else if (! _invalid)
{
// 渲染场景
drawScene(); // release the objects
// 释放对象:内存池里之前通过autorelease加入的对象引用计数减 1.
PoolManager::getInstance()->getCurrentPool()->clear();
}
}
mainLoop主要完成三个动作:
1 判断是否需要释放 CCDirector，如果需要，则删除 CCDirector 占用的资源。通常，游戏结束时才会执行这个步骤。
2 调用 drawScene()方法，绘制当前场景并进行其他必要的处理。
3 弹出自动回收池，使得这一帧被放入自动回收池的对象全部释放。
(1-2-2-1) 由此可见，mainLoop()把内存管理以外的操作都交给了 drawScene()方法，因此关键的步骤都在 drawScene()方法之中。下面是 drawScene()方法的实现：
// Draw the Scene
void Director::drawScene()
{
// calculate "global" dt
// 计算全局帧间时间差 dt
calculateDeltaTime(); // skip one flame when _deltaTime equal to zero.
if(_deltaTime < FLT_EPSILON)
{
return;
} if (_openGLView)
{
_openGLView->pollInputEvents();
} //tick before glClear: issue #533
if (! _paused)
{
// 启动定时器
_scheduler->update(_deltaTime);
_eventDispatcher->dispatchEvent(_eventAfterUpdate);
} glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); /* to avoid flickr, nextScene MUST be here: after tick and before draw.
XXX: Which bug is this one. It seems that it can't be reproduced with v0.9 */
if (_nextScene)
{
// 如果有,设置下一个场景
setNextScene();
}
// 保存原来的模型视图(ModelView)矩阵
pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW); // draw the scene
if (_runningScene)
{
// 开始绘制场景
_runningScene->visit(_renderer, Mat4::IDENTITY, false);
// 事件分发
_eventDispatcher->dispatchEvent(_eventAfterVisit);
} // draw the notifications node
if (_notificationNode)
{
// 处理通知节点
_notificationNode->visit(_renderer, Mat4::IDENTITY, false);
} if (_displayStats)
{
showStats();
}
// 开始渲染场景
_renderer->render();
_eventDispatcher->dispatchEvent(_eventAfterDraw); popMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW); _totalFrames++; // swap buffers 交换缓冲区
if (_openGLView)
{
_openGLView->swapBuffers();
} if (_displayStats)
{
calculateMPF();
}
}
可以发现drawScene主要用于处理 OpenGL 和一些细节，如计算 FPS、帧间时间差等,这里我们主要进行了以下 3 个操作。
1 调用了定时调度器的 update 方法，引发定时器事件。
2 如果场景需要被切换，则调用 setNextScene 方法，在显示场景前切换场景。
3 调用当前场景的 visit 方法，将当前场景加入渲染队列,并通过render统一渲染。
(1-2-2-1-1) 我们进入到visit方法里面,看它怎样把每一个节点添加到渲染队列, 这里我们找到/cocos2d-x-3.2/cocos/2d/CCNode.cpp:
void Node::visit(Renderer* renderer, const Mat4 &parentTransform, uint32_t parentFlags)
{
// quick return if not visible. children won't be drawn.
if (!_visible)
{
return;
}
// 设置_modelViewTransform矩阵
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* director = Director::getInstance();
director->pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);
director->loadMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW, _modelViewTransform); int i = ; if(!_children.empty())
{
sortAllChildren();
// draw children zOrder < 0
for( ; i < _children.size(); i++ )
{
auto node = _children.at(i); if ( node && node->_localZOrder < )
node->visit(renderer, _modelViewTransform, flags);
else
break;
}
// self draw
this->draw(renderer, _modelViewTransform, flags); for(auto it=_children.cbegin()+i; it != _children.cend(); ++it)
(*it)->visit(renderer, _modelViewTransform, flags);
}
else
{
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;
}
(1-2-2-1-1-1) 对节点的所有孩子排序,通过调用draw函数,首先绘制ZOrder<0的节点,在绘制自身,最后绘制ZOrder>0的节点. 我们进入draw看看它做些什么. 注意,visit和draw都是虚函数, 以sprite为例,我们进入到/cocos2d-x-3.2/cocos/2d/CCSprite.cpp:
void Sprite::draw(Renderer *renderer, const Mat4 &transform, uint32_t flags)
{
// Don't do calculate the culling if the transform was not updated
_insideBounds = (flags & FLAGS_TRANSFORM_DIRTY) ? renderer->checkVisibility(transform, _contentSize) : _insideBounds; if(_insideBounds)
{
_quadCommand.init(_globalZOrder, _texture->getName(), getGLProgramState(), _blendFunc, &_quad, , transform);
renderer->addCommand(&_quadCommand);
//物理引擎相关绘制边界
#if CC_SPRITE_DEBUG_DRAW
_customDebugDrawCommand.init(_globalZOrder);
_customDebugDrawCommand.func = CC_CALLBACK_0(Sprite::drawDebugData, this);
renderer->addCommand(&_customDebugDrawCommand);
#endif //CC_SPRITE_DEBUG_DRAW
}
}
(1-2-2-1-1-1-1) 从代码中可以看出,Sprite的draw函数里面并没有做实际的渲染工作,而是用QuadCommand命令将渲染操作打包,加入到渲染队列里面,在drawscene最后通过调用render()进行统一渲染;我们可以看看_quadCommand.init里面究竟做了什么,找到/cocos2d-x-3.2/cocos/renderer/CCQuadCommand.cpp:
void QuadCommand::init(float globalOrder, GLuint textureID, GLProgramState* glProgramState, BlendFunc blendType, V3F_C4B_T2F_Quad* quad, ssize_t quadCount, const Mat4 &mv)
{
CCASSERT(glProgramState, "Invalid GLProgramState");
CCASSERT(glProgramState->getVertexAttribsFlags() == , "No custom attributes are supported in QuadCommand"); _globalOrder = globalOrder; _quadsCount = quadCount;
_quads = quad; // 设置MV矩阵
_mv = mv; if( _textureID != textureID || _blendType.src != blendType.src || _blendType.dst != blendType.dst || _glProgramState != glProgramState) {
//
_textureID = textureID;
// _blendType就是我们的BlendFunc混合函数
_blendType = blendType;
_glProgramState = glProgramState; // 生成材质ID
generateMaterialID();
}
}
(1-2-2-1-1-1-1-1) 我们在进入到generateMaterialID()函数里面看看:
void QuadCommand::generateMaterialID()
{ if(_glProgramState->getUniformCount() > )
{
_materialID = QuadCommand::MATERIAL_ID_DO_NOT_BATCH;
}
else
{
int glProgram = (int)_glProgramState->getGLProgram()->getProgram();
int intArray[] = { glProgram, (int)_textureID, (int)_blendType.src, (int)_blendType.dst}; _materialID = XXH32((const void*)intArray, sizeof(intArray), );
}
}
从这里我们可以看出, 我们的材质ID（_materialID）最终是要由shader（glProgram）、混合类型（_blendType）、纹理ID（_textureID）组成的, 所以这三样东西如果有谁不一样的话，那就无法生成相同的材质ID，也就无法在同一 个批次里进行渲染了。
(1-2-2-1-2) 现在,我们回到(1-2-2-1-1-1)的draw函数, 通过上面将渲染指令初始化之后,就是将打包好的渲染命令添加到渲染队列里面了.这里只需简单调用renderer->addCommand(&_quadCommand);即可. 这样,(1-2-2-1)处的drawscene函数中,visit通过调用派生类节点添加渲染指令到渲染队列的工作已经完成了.接下来要做的就是做实际的渲染工作了.3.x版本与之前版本不同,是在drawscene最后通过调用render()函数进行统一渲染的,我们进入render()看一下,找到cocos2d-x-3.2/cocos/renderer/CCRenderer.cpp:
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)
{
// cleanup
_drawnBatches = _drawnVertices = ; //Process render commands
//1. Sort render commands based on ID
for (auto &renderqueue : _renderGroups)
{
renderqueue.sort();
}
visitRenderQueue(_renderGroups[]);
flush();
}
clean();
_isRendering = false;
}
从代码可以看出,从Cocos2d-x3.0开始，Cocos2d-x引入了新的渲染流程，它不像2.x版本 直接在每一个node中的draw函数中直接调用OpenGL代码进行图形渲染，而是通过各种RenderCommand封装起来，然后添加到一个 CommandQueue队列里面去，而现在draw函数的作用就是在此函数中设置好相对应的RenderCommand参数，然后把此 RenderCommand添加到CommandQueue中。最后在每一帧结束时调用renderer函数进行渲染，在renderer函数中会根据 ID对RenderCommand进行排序，然后才进行渲染。
(1-2-2-1-2-1) 现在我们进入visitRenderQueue函数看看它做了什么动作:
void Renderer::visitRenderQueue(const RenderQueue& queue)
{
ssize_t size = queue.size(); for (ssize_t index = ; index < size; ++index)
{
auto command = queue[index];
auto commandType = command->getType();
if(RenderCommand::Type::QUAD_COMMAND == commandType)
{
flush3D();
auto cmd = static_cast<QuadCommand*>(command);
//Batch quads
// 如果Quad数据量超过VBO的大小，那么调用绘制，将缓存的命令全部绘制
if(_numQuads + cmd->getQuadCount() > VBO_SIZE)
{
CCASSERT(cmd->getQuadCount()>= && cmd->getQuadCount() < VBO_SIZE, "VBO is not big enough for quad data, please break the quad data down or use customized render command"); //Draw batched quads if VBO is full
drawBatchedQuads();
}
// 这个处理主要是把命令存入_batchedQuadCommands中，如果如果Quad数据量超过VBO的大小，那么调用绘制，将缓存的命令全部绘制.
// 如果一直没有超过VBO的大小，drawBatchedQuads绘制函数将在flush被调用时调用.
//将命令缓存起来，先不调用绘制
_batchedQuadCommands.push_back(cmd); memcpy(_quads + _numQuads, cmd->getQuads(), sizeof(V3F_C4B_T2F_Quad) * cmd->getQuadCount());
// 通过MV矩阵,转换成世界坐标
convertToWorldCoordinates(_quads + _numQuads, cmd->getQuadCount(), cmd->getModelView());// 记录下四边形数量
_numQuads += cmd->getQuadCount(); }
else if(RenderCommand::Type::GROUP_COMMAND == commandType)
{
flush();
int renderQueueID = ((GroupCommand*) command)->getRenderQueueID();
visitRenderQueue(_renderGroups[renderQueueID]);
}
else if(RenderCommand::Type::CUSTOM_COMMAND == commandType)
{
flush();
auto cmd = static_cast<CustomCommand*>(command);
cmd->execute();
}
else if(RenderCommand::Type::BATCH_COMMAND == commandType)
{
flush();
auto cmd = static_cast<BatchCommand*>(command);
cmd->execute();
}
else if (RenderCommand::Type::MESH_COMMAND == commandType)
{
flush2D();
auto cmd = static_cast<MeshCommand*>(command);
if (_lastBatchedMeshCommand == nullptr || _lastBatchedMeshCommand->getMaterialID() != cmd->getMaterialID())
{
flush3D();
cmd->preBatchDraw();
cmd->batchDraw();
_lastBatchedMeshCommand = cmd;
}
else
{
cmd->batchDraw();
}
}
else
{
CCLOGERROR("Unknown commands in renderQueue");
}
}
}
从代码中，我们看到RenderCommand类型有QUAD_COMMAND,CUSTOM_COMMAND,BATCH_COMMAND,GROUP_COMMAND,MESH_COMMAND五种，OpenGL的API调用是在Renderer::drawBatchedQuads()、BatchCommand::execute()中。通过上面代码的注释,可以看到最常用的QUAD_COMMAND类型的渲染命令的处理过程.
(1-2-2-1-2-1-1) 如果Quad数据量超过VBO的大小(VBO_SIZE = 65536 / 6;), 则会调用drawBatchedQuads进行批量渲染:
void Renderer::drawBatchedQuads()
{
//TODO we can improve the draw performance by insert material switching command before hand. int quadsToDraw = ;
int startQuad = ; //Upload buffer to VBO
if(_numQuads <= || _batchedQuadCommands.empty())
{
return;
}
// 是否支持VAO
if (Configuration::getInstance()->supportsShareableVAO())
{
//Set VBO data 绑定VBO数据, 激活缓冲区对象
glBindBuffer(GL_ARRAY_BUFFER, _buffersVBO[]); // 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(quads_[0]) * (n-start), &quads_[start], GL_DYNAMIC_DRAW); // option 3: orphaning + glMapBuffer
// 用数据分配和初始化缓冲区对象
glBufferData(GL_ARRAY_BUFFER, sizeof(_quads[]) * (_numQuads), nullptr, GL_DYNAMIC_DRAW);
// OPENGL 缓冲区对象（buffer object），允许应用程序显式地指定把哪些数据存储在图形服务器或显存中
// 返回指向缓冲区的指针, 缓冲一经具体使用之后，只需要改变缓冲区的内容，即在glMapBuffer和glUnmapBuffer之间改变数据即可
void *buf = glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
memcpy(buf, _quads, sizeof(_quads[])* (_numQuads));
glUnmapBuffer(GL_ARRAY_BUFFER);
// 解除绑定
glBindBuffer(GL_ARRAY_BUFFER, ); //Bind VAO 绑定VAO
GL::bindVAO(_quadVAO);
}
else
{
#define kQuadSize sizeof(_quads[0].bl)
glBindBuffer(GL_ARRAY_BUFFER, _buffersVBO[]); glBufferData(GL_ARRAY_BUFFER, sizeof(_quads[]) * _numQuads , _quads, GL_DYNAMIC_DRAW); GL::enableVertexAttribs(GL::VERTEX_ATTRIB_FLAG_POS_COLOR_TEX); // vertices
glVertexAttribPointer(GLProgram::VERTEX_ATTRIB_POSITION, , GL_FLOAT, GL_FALSE, kQuadSize, (GLvoid*) offsetof(V3F_C4B_T2F, vertices)); // colors
glVertexAttribPointer(GLProgram::VERTEX_ATTRIB_COLOR, , GL_UNSIGNED_BYTE, GL_TRUE, kQuadSize, (GLvoid*) offsetof(V3F_C4B_T2F, colors)); // tex coords
glVertexAttribPointer(GLProgram::VERTEX_ATTRIB_TEX_COORD, , GL_FLOAT, GL_FALSE, kQuadSize, (GLvoid*) offsetof(V3F_C4B_T2F, texCoords)); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _buffersVBO[]);
} //Start drawing verties in batch
for(const auto& cmd : _batchedQuadCommands)
{
auto newMaterialID = cmd->getMaterialID();
if(_lastMaterialID != newMaterialID || newMaterialID == QuadCommand::MATERIAL_ID_DO_NOT_BATCH)
{
//Draw quads
if(quadsToDraw > )
{
// 四边形都可以由2个三角形组合而成,指定6个索引点(画出2个GL_TRIANGLES)
glDrawElements(GL_TRIANGLES, (GLsizei) quadsToDraw*, GL_UNSIGNED_SHORT, (GLvoid*) (startQuad**sizeof(_indices[])) );
_drawnBatches++;
_drawnVertices += quadsToDraw*; startQuad += quadsToDraw;
quadsToDraw = ;
} //Use new material
cmd->useMaterial();
_lastMaterialID = newMaterialID;
} quadsToDraw += cmd->getQuadCount();
} //Draw any remaining quad
if(quadsToDraw > )
{
// 画剩下的四边形
glDrawElements(GL_TRIANGLES, (GLsizei) quadsToDraw*, GL_UNSIGNED_SHORT, (GLvoid*) (startQuad**sizeof(_indices[])) );
_drawnBatches++;
_drawnVertices += quadsToDraw*;
} if (Configuration::getInstance()->supportsShareableVAO())
{
//Unbind VAO 接除绑定VAO
GL::bindVAO();
}
else
{
glBindBuffer(GL_ARRAY_BUFFER, );
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, );
} _batchedQuadCommands.clear();
_numQuads = ;
}
附注:5种渲染类型:
1. QUAD_COMMAND：QuadCommand类绘制精灵等。所有绘制图片的命令都会调用到这里，处理这个类型命令的代码就是绘制贴图的openGL代码。
2. CUSTOM_COMMAND：CustomCommand类自定义绘制，自己定义绘制函数，在调用绘制时只需调用已经传进来的回调函数就可以，裁剪节点，绘制图形节点都采用这个绘制，把绘制函数定义在自己的类里。这种类型的绘制命令不会在处理命令的时候调用任何一句openGL代码，而是调用你写好并设置给func的绘制函数。
3. BATCH_COMMAND：BatchCommand类批处理绘制，批处理精灵和粒子,其实它类似于自定义绘制，也不会再render函数中出现任何一句openGL函数。
4. GROUP_COMMAND：GroupCommand类绘制组，一个节点包括两个以上绘制命令的时候，把这个绘制命令存储到另外一个_renderGroups中的元素中，并把这个元素的指针作为一个节点存储到_renderGroups[0]中。
5. MESH_COMMAND :