本文详细介绍了OpenGL绘图框架，包括创建窗口、设置像素格式、激活渲染环境等关键步骤。核心内容在于绘制基本图元，如三角形和正方形，并解释了如何通过glTranslatef进行坐标变换以实现对象的平移。
第一篇笔记中的OpenGL框架其实很简单，大致有如下几个步骤：<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
1，取得窗口的实例，然后定义窗口类
2，注册窗口类
3,创建窗口
4,描述像素格式
5，获取设备描述表
6，找到与此前我们选定的象素格式相对应的象素格式
7，设置象素格式
8，取得绘制描述表
9，激活绘制描述表
10,显示窗口
11,将屏幕的宽度和高度设置给透视OpenGL屏幕(设置视口，进行投影，模型透视）
其他就是对窗口事件的处理了，尤其是重画事件(WM_PAINT等)，但只是画了一个空窗口，现在加一些代码来画简单的基本图元。：
OpenGL框架完整代码
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#include<windows.h>#include<GL/gl.h>#include<GL/glu.h>#include<GL/glaux.h>HINSTANCEhInstance;//当前程序实例HDChDC=NULL;//设备环境HGLRChRC=NULL;//绘制环境HWNDhWnd=NULL;//窗口句柄boolkeys[256];boolactive=TRUE;LRESULTCALLBACKWndProc(HWND,UINT,WPARAM,LPARAM);GLvoidReSizeGLScene(GLsizeiwidth,GLsizeiheight)//ResizeAndInitializeTheGLWindow
{
if(height==0)//PreventADivideByZeroBy
{height=1;//MakingHeightEqualOne
}glViewport(0,0,width,height);//ResetTheCurrentViewportglMatrixMode(GL_PROJECTION);//SelectTheProjectionMatrixglLoadIdentity();//ResetTheProjectionMatrix//CalculateTheAspectRatioOfTheWindowgluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);glMatrixMode(GL_MODELVIEW);//SelectTheModelviewMatrixglLoadIdentity();//ResetTheModelviewMatrix
}intInitGL(GLvoid)//AllSetupForOpenGLGoesHere{glShadeModel(GL_SMOOTH);//EnableSmoothShadingglClearColor(0.3f,0.0f,0.5f,0.5f);//BlackBackgroundglClearDepth(1.0f);//DepthBufferSetupglEnable(GL_DEPTH_TEST);//EnablesDepthTestingglDepthFunc(GL_LEQUAL);//TheTypeOfDepthTestingToDoglHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_NICEST);//ReallyNicePerspectiveCalculationsreturnTRUE;//InitializationWentOK}intDrawGLScene(GLvoid)//Here'sWhereWeDoAllTheDrawing{glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);//ClearScreenAndDepthBufferglLoadIdentity();glTranslatef(-1.5f,0.0f,-6.0f);//MoveLeft1.5UnitsAndIntoTheScreen6.0glBegin(GL_TRIANGLES);//DrawingUsingTrianglesglVertex3f(0.0f,1.0f,0.0f);//TopglVertex3f(-1.0f,-1.0f,0.0f);//BottomLeftglVertex3f(1.0f,-1.0f,0.0f);//BottomRightglEnd();//FinishedDrawingTheTriangleglTranslatef(3.0f,0.0f,0.0f);//MoveRight3UnitsglBegin(GL_QUADS);//DrawAQuadglVertex3f(-1.0f,1.0f,0.0f);//TopLeftglVertex3f(1.0f,1.0f,0.0f);//TopRightglVertex3f(1.0f,-1.0f,0.0f);//BottomRightglVertex3f(-1.0f,-1.0f,0.0f);//BottomLeftglEnd();//DoneDrawingTheQuad//ResetTheCurrentModelviewMatrixreturnTRUE;//EverythingWentOK}GLvoidKillGLWindow(GLvoid)//ProperlyKillTheWindow{if(hRC)//DoWeHaveARenderingContext?{if(!wglMakeCurrent(NULL,NULL))//AreWeAbleToReleaseTheDCAndRCContexts?{MessageBox(NULL,"ReleaseOfDCAndRCFailed.","SHUTDOWNERROR",MB_OK|MB_ICONINFORMATION);}if(!wglDeleteContext(hRC))//AreWeAbleToDeleteTheRC?{MessageBox(NULL,"ReleaseRenderingContextFailed.","SHUTDOWNERROR",MB_OK|MB_ICONINFORMATION);}hRC=NULL;//SetRCToNULL}if(hDC&&!ReleaseDC(hWnd,hDC))//AreWeAbleToReleaseTheDC{MessageBox(NULL,"ReleaseDeviceContextFailed.","SHUTDOWNERROR",MB_OK|MB_ICONINFORMATION);hDC=NULL;//SetDCToNULL}if(hWnd&&!DestroyWindow(hWnd))//AreWeAbleToDestroyTheWindow?{MessageBox(NULL,"CouldNotReleasehWnd.","SHUTDOWNERROR",MB_OK|MB_ICONINFORMATION);hWnd=NULL;//SethWndToNULL}if(!UnregisterClass("OpenGL",hInstance))//AreWeAbleToUnregisterClass{MessageBox(NULL,"CouldNotUnregisterClass.","SHUTDOWNERROR",MB_OK|MB_ICONINFORMATION);hInstance=NULL;//SethInstanceToNULL}}BOOLCreateGLWindow(char*title,intwidth,intheight,intbits){/**//*title:窗口标题;width:窗口宽度;height:窗口高度;bits:每象素所选的色彩深度*/GLuintPixelFormat;WNDCLASSwc;DWORDdwExStyle;DWORDdwStyle;RECTWindowRect;WindowRect.left=(long)0;WindowRect.right=(long)width;WindowRect.top=(long)0;WindowRect.bottom=(long)height;hInstance=GetModuleHandle(NULL);wc.style=CS_HREDRAW|CS_VREDRAW|CS_OWNDC;wc.lpfnWndProc=(WNDPROC)WndProc;wc.cbClsExtra=0;wc.cbWndExtra=0;wc.hInstance=hInstance;wc.hIcon=LoadIcon(NULL,IDI_WINLOGO);wc.hCursor=LoadCursor(NULL,IDC_ARROW);wc.hbrBackground=NULL;wc.lpszMenuName=NULL;wc.lpszClassName="OpenGL";if(!RegisterClass(&wc)){MessageBox(NULL,"无法注册窗口类!!!","ERROR",MB_OK|MB_ICONEXCLAMATION);returnFALSE;}dwExStyle=WS_EX_APPWINDOW|WS_EX_WINDOWEDGE;dwStyle=WS_OVERLAPPEDWINDOW;AdjustWindowRectEx(&WindowRect,dwExStyle,FALSE,dwStyle);if(!(hWnd=CreateWindowEx(dwExStyle,//ExtendedStyleForTheWindow"OpenGL",//ClassNametitle,//WindowTitledwStyle|//DefinedWindowStyleWS_CLIPSIBLINGS|//RequiredWindowStyleWS_CLIPCHILDREN,//RequiredWindowStyle0,0,//WindowPositionWindowRect.right-WindowRect.left,//CalculateWindowWidthWindowRect.bottom-WindowRect.top,//CalculateWindowHeightNULL,//NoParentWindowNULL,//NoMenuhInstance,//InstanceNULL)))//DontPassAnythingToWM_CREATE{MessageBox(NULL,"创建窗口失败","ERROR",MB_OK|MB_ICONEXCLAMATION);returnFALSE;}staticPIXELFORMATDESCRIPTORpfd=//pfdTellsWindowsHowWeWantThingsToBe{sizeof(PIXELFORMATDESCRIPTOR),//SizeOfThisPixelFormatDescriptor1,//VersionNumberPFD_DRAW_TO_WINDOW|//FormatMustSupportWindowPFD_SUPPORT_OPENGL|//FormatMustSupportOpenGLPFD_DOUBLEBUFFER,//MustSupportDoubleBufferingPFD_TYPE_RGBA,//RequestAnRGBAFormatbits,//SelectOurColorDepth0,0,0,0,0,0,//ColorBitsIgnored0,//NoAlphaBuffer0,//ShiftBitIgnored0,//NoAccumulationBuffer0,0,0,0,//AccumulationBitsIgnored16,//16BitZ-Buffer(DepthBuffer)0,//NoStencilBuffer0,//NoAuxiliaryBufferPFD_MAIN_PLANE,//MainDrawingLayer0,//Reserved0,0,0//LayerMasksIgnored};if(!(hDC=GetDC(hWnd))){KillGLWindow();MessageBox(NULL,"无法创建GL设备环境.","ERROR",MB_OK|MB_ICONEXCLAMATION);returnFALSE;}if(!(PixelFormat=ChoosePixelFormat(hDC,&pfd)))//DidWindowsFindAMatchingPixelFormat?{KillGLWindow();//ResetTheDisplayMessageBox(NULL,"无法找到合适的像素格式.","ERROR",MB_OK|MB_ICONEXCLAMATION);returnFALSE;//ReturnFALSE}if(!SetPixelFormat(hDC,PixelFormat,&pfd))//AreWeAbleToSetThePixelFormat?{KillGLWindow();//ResetTheDisplayMessageBox(NULL,"像素格式无法设置.","ERROR",MB_OK|MB_ICONEXCLAMATION);returnFALSE;//ReturnFALSE}if(!(hRC=wglCreateContext(hDC)))//AreWeAbleToGetARenderingContext?{KillGLWindow();//ResetTheDisplayMessageBox(NULL,"无法创建一个绘制环境.","ERROR",MB_OK|MB_ICONEXCLAMATION);returnFALSE;//ReturnFALSE}if(!wglMakeCurrent(hDC,hRC))//TryToActivateTheRenderingContext{KillGLWindow();//ResetTheDisplayMessageBox(NULL,"无法激活绘制环境.","ERROR",MB_OK|MB_ICONEXCLAMATION);returnFALSE;//ReturnFALSE}ShowWindow(hWnd,SW_SHOW);SetForegroundWindow(hWnd);SetFocus(hWnd);ReSizeGLScene(width,height);if(!InitGL())//初始化新建的GL窗口{KillGLWindow();//重置显示区MessageBox(NULL,"InitializationFailed.","ERROR",MB_OK|MB_ICONEXCLAMATION);returnFALSE;//返回FALSE}returnTRUE;}LRESULTCALLBACKWndProc(HWNDhWnd,//HandleForThisWindowUINTuMsg,//MessageForThisWindowWPARAMwParam,//AdditionalMessageInformationLPARAMlParam)//AdditionalMessageInformation{switch(uMsg)//CheckForWindowsMessages{caseWM_ACTIVATE://WatchForWindowActivateMessage{if(!HIWORD(wParam))//CheckMinimizationState{active=TRUE;//ProgramIsActive}else{active=FALSE;//ProgramIsNoLongerActive}return0;//ReturnToTheMessageLoop}caseWM_SYSCOMMAND://InterceptSystemCommands{switch(wParam)//CheckSystemCalls{caseSC_SCREENSAVE://ScreensaverTryingToStart?caseSC_MONITORPOWER://MonitorTryingToEnterPowersave?return0;//PreventFromHappening}break;//Exit}caseWM_CLOSE://DidWeReceiveACloseMessage?{PostQuitMessage(0);//SendAQuitMessagereturn0;//JumpBack}caseWM_KEYDOWN://IsAKeyBeingHeldDown?{keys[wParam]=TRUE;//IfSo,MarkItAsTRUEreturn0;//JumpBack}caseWM_KEYUP://HasAKeyBeenReleased?{keys[wParam]=FALSE;//IfSo,MarkItAsFALSEreturn0;//JumpBack}caseWM_SIZE://ResizeTheOpenGLWindow{ReSizeGLScene(LOWORD(lParam),HIWORD(lParam));//LoWord=Width,HiWord=Heightreturn0;//JumpBack}}//PassAllUnhandledMessagesToDefWindowProcreturnDefWindowProc(hWnd,uMsg,wParam,lParam);}intWINAPIWinMain(HINSTANCEhInstance,HINSTANCEhPrevInstance,LPSTRlpCmdLine,intnShowCmd){MSGmsg;//WindowsMessageStructureBOOLdone=FALSE;//BoolVariableToExitLoop//CreateOurOpenGLWindowif(!CreateGLWindow("NeHe'sOpenGLFramework",640,480,16)){return0;//QuitIfWindowWasNotCreated}while(!done)//LoopThatRunsWhiledone=FALSE{if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))//IsThereAMessageWaiting?{if(msg.message==WM_QUIT)//HaveWeReceivedAQuitMessage?{done=TRUE;//IfSodone=TRUE}else//IfNot,DealWithWindowMessages{TranslateMessage(&msg);//TranslateTheMessageDispatchMessage(&msg);//DispatchTheMessage}}else//IfThereAreNoMessages{//DrawTheScene.WatchForESCKeyAndQuitMessagesFromDrawGLScene()if(active)//ProgramActive?{if(keys[VK_ESCAPE])//WasESCPressed?{done=TRUE;//ESCSignalledAQuit}else//NotTimeToQuit,UpdateScreen{DrawGLScene();//DrawTheSceneSwapBuffers(hDC);//SwapBuffers(DoubleBuffering)}}}}//ShutdownKillGLWindow();//KillTheWindowreturn(msg.wParam);//ExitTheProgram}
其中最核心的代码是：
int
DrawGLScene(GLvoid)
//
Here'sWhereWeDoAllTheDrawing
{glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);//ClearScreenAndDepthBufferglLoadIdentity();glTranslatef(-1.5f,0.0f,-6.0f);//MoveLeft1.5UnitsAndIntoTheScreen6.0glBegin(GL_TRIANGLES);//DrawingUsingTrianglesglVertex3f(0.0f,1.0f,0.0f);//TopglVertex3f(-1.0f,-1.0f,0.0f);//BottomLeftglVertex3f(1.0f,-1.0f,0.0f);//BottomRightglEnd();//FinishedDrawingTheTriangleglTranslatef(3.0f,0.0f,0.0f);//MoveRight3UnitsglBegin(GL_QUADS);//DrawAQuadglVertex3f(-1.0f,1.0f,0.0f);//TopLeftglVertex3f(1.0f,1.0f,0.0f);//TopRightglVertex3f(1.0f,-1.0f,0.0f);//BottomRightglVertex3f(-1.0f,-1.0f,0.0f);//BottomLeftglEnd();//DoneDrawingTheQuad//ResetTheCurrentModelviewMatrixreturnTRUE;//EverythingWentOK}
按照我的个人理解，，就好比照相机拍照一样，被拍的物体移动和照相机反方向移动可以得到相同的效果(使得成像的大小变化)，这里的glTranslatef是用来进行造型变换的（类似移动物体却不移动照相机）。通过改变平移值的大小可以明显看出平移的效果。
这里要注意的是存在两种不同的坐标变换方式，glTranslatef(x,y,z)中的x，y，z是相对与当前所在点的位移，但glVertex(x,y,z)是相对于glTranslatef(x,y,z)移动后的新原点的位移。因而这里可以认为glTranslate移动的是坐标原点，glVertex中的点是相对最新的坐标原点的坐标值。
当调用glLoadIdentity()之后，实际上将当前点移到了屏幕中心，X坐标轴从左至右，Y坐标轴从下至上，Z坐标轴从里至外。OpenGL屏幕中心的坐标值是X和Y轴上的<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><chmetcnv unitname="F" sourcevalue="0" hasspace="False" negative="False" numbertype="1" tcsc="0" w:st="on"><span lang="EN-US" style="FONT-SIZE: 10pt; FONT-FAMILY: Verdana">0.0f</span></chmetcnv>点。中心左面的坐标值是负值，右面是正值。移向屏幕顶端是正值，移向屏幕底端是负值。移入屏幕深处是负值，移出屏幕则是正值。
glTranslatef(x, y, z)沿着X，Y和Z轴移动。根据前面的次序，下面的代码沿着X轴左移1.5个单位，Y轴不动(<chmetcnv unitname="F" sourcevalue="0" hasspace="False" negative="False" numbertype="1" tcsc="0" w:st="on">0.0f</chmetcnv>)，最后移入屏幕<chmetcnv unitname="F" sourcevalue="6" hasspace="False" negative="False" numbertype="1" tcsc="0" w:st="on"><span lang="EN-US" style="FONT-SIZE: 10pt; FONT-FAMILY: Verdana">6.0f</span></chmetcnv>个单位。注意在glTranslatef(x, y, z)中当移动的时候，并不是相对屏幕中心移动，而是相对与当前所在的屏幕位置。
glTranslatef(<chmetcnv unitname="F" sourcevalue="1.5" hasspace="False" negative="True" numbertype="1" tcsc="0" w:st="on">-<chmetcnv unitname="F" sourcevalue="1.5" hasspace="False" negative="False" numbertype="1" tcsc="0" w:st="on">1.5f</chmetcnv></chmetcnv>,<chmetcnv unitname="F" sourcevalue="0" hasspace="False" negative="False" numbertype="1" tcsc="0" w:st="on">0.0f</chmetcnv>,<chmetcnv unitname="F" sourcevalue="6" hasspace="False" negative="True" numbertype="1" tcsc="0" w:st="on">-<chmetcnv unitname="F" sourcevalue="6" hasspace="False" negative="False" numbertype="1" tcsc="0" w:st="on">6.0f</chmetcnv></chmetcnv>); // 左移1.5单位，并移入屏幕6.0
现在我们已经移到了屏幕的左半部分，并且将视图推入屏幕背后足够的距离以便我们可以看见全部的场景－创建三角形。
在屏幕的左半部分画完三角形后，我们要移到右半部分来画正方形。为此要再次使用glTranslate。这次右移，所以X坐标值为正值。因为前面左移了1.5个单位，这次要先向右移回屏幕中心（1.5个单位），再向右移动1.5个单位。总共要向右移3.0个单位。
glTranslatef(<chmetcnv unitname="F" sourcevalue="3" hasspace="False" negative="False" numbertype="1" tcsc="0" w:st="on">3.0f</chmetcnv>,<chmetcnv unitname="F" sourcevalue="0" hasspace="False" negative="False" numbertype="1" tcsc="0" w:st="on">0.0f</chmetcnv>,<chmetcnv unitname="F" sourcevalue="0" hasspace="False" negative="False" numbertype="1" tcsc="0" w:st="on">0.0f</chmetcnv>); // 右移3单位
还有一点值得特别注意：我们使用顺时针次序来画正方形－左上－右上－右下－左下。采用顺时针绘制的是对象的后表面。这就是说我们所看见的是正方形的背面。逆时针画出来的正方形才是正面朝着我们的。
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