cocos2dx 2.x 每帧渲染分析

1、java端

1、Cocos2dxRenderer类
	@Override
	public void onDrawFrame(final GL10 gl) {
		/*
		 * No need to use algorithm in default(60 FPS) situation,* since onDrawFrame() was called by system 60 times per second by default.
		 */
		if (sAnimationInterval <= 1.0 / 60 * Cocos2dxRenderer.NANOSECONDSPERSECOND) {
			Cocos2dxRenderer.nativeRender();
		} else {
			final long now = System.nanoTime();
			final long remain = mLastTickInNanoSeconds + Cocos2dxRenderer.sAnimationInterval - now;
			if (remain > 0) {
				try {
					Thread.sleep(remain / Cocos2dxRenderer.NANOSECONDSPERMICROSECOND);
				} catch (final Exception e) {
				}
			}
			/*
			 * Render time MUST be counted in,or the FPS will slower than appointed.
			*/
			mLastTickInNanoSeconds = System.nanoTime();
			Cocos2dxRenderer.nativeRender(); //调用C++部分的函数
		}
	}

 JNIEXPORT void JNICALL Java_org_cocos2dx_lib_Cocos2dxRenderer_nativeRender(JNIEnv* env) {
        cocos2d::CCDirector::sharedDirector()->mainLoop();
    }

    -->> mainLoop函数
    void CCDisplayLinkDirector::mainLoop(void)
{
    if (m_bPurgeDirecotorInNextLoop)
    {
        m_bPurgeDirecotorInNextLoop = false;
        purgeDirector();
    }
    else if (! m_bInvalid)
     {
         drawScene();
     
         // release the objects
         CCPoolManager::sharedPoolManager()->pop();        
     }
}

-->>drawScene渲染
// Draw the Scene
void CCDirector::drawScene(void)
{
    // calculate "global" dt
    calculateDeltaTime();

    //tick before glClear: issue #533
    if (! m_bPaused) //定时器相关，以后说
    {
        m_pScheduler->update(m_fDeltaTime);
    }

    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 (m_pNextScene)
    {
        setNextScene();
    }

    kmGLPushMatrix();

    // draw the scene 渲染
    if (m_pRunningScene)
    {
        m_pRunningScene->visit();
    }

    // draw the notifications node
    if (m_pNotificationNode)
    {
        m_pNotificationNode->visit();
    }
    
    if (m_bDisplayStats)
    {
        showStats();
    }
    
    kmGLPopMatrix();

    m_uTotalFrames++;

    // swap buffers
    if (m_pobOpenGLView)
    {
        m_pobOpenGLView->swapBuffers();
    }
    
    if (m_bDisplayStats)
    {
        calculateMPF();
    }
}

-->>visit函数，遍历UI树，调用visit和draw进行每个node的渲染
void CCNode::visit()
{
    // quick return if not visible. children won't be drawn.
    if (!m_bVisible)
    {
        return;
    }
    kmGLPushMatrix();

     if (m_pGrid && m_pGrid->isActive())
     {
         m_pGrid->beforeDraw();
     }

    this->transform();

    CCNode* pNode = NULL;
    unsigned int i = 0;

    if(m_pChildren && m_pChildren->count() > 0)
    {
        sortAllChildren();
        // draw children zOrder < 0
        ccArray *arrayData = m_pChildren->data;
        for( ; i < arrayData->num; i++ )
        {
            pNode = (CCNode*) arrayData->arr[i];

            if ( pNode && pNode->m_nZOrder < 0 ) 
            {
                pNode->visit();
            }
            else
            {
                break;
            }
        }
        // self draw
        this->draw();

        for( ; i < arrayData->num; i++ )
        {
            pNode = (CCNode*) arrayData->arr[i];
            if (pNode)
            {
                pNode->visit();
            }
        }        
    }
    else
    {
        this->draw();
    }

    // reset for next frame
    m_uOrderOfArrival = 0;

     if (m_pGrid && m_pGrid->isActive())
     {
         m_pGrid->afterDraw(this);
    }
 
    kmGLPopMatrix();
}

（编辑：李大同）

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