OpenGL入门笔记（一）

#include<windows.h>//HeaderFileForWindows
#include<gl/gl.h>//HeaderFileForTheOpenGL32Library
#include<gl/glu.h>//HeaderFileForTheGLu32Library
#include<gl/glaux.h>//HeaderFileForTheGlauxLibrary

HDChDC=NULL;//PrivateGDIDeviceContext
HGLRChRC=NULL;//PermanentRenderingContext
HWNDhWnd=NULL;//HoldsOurWindowHandle
HINSTANCEhInstance;//HoldsTheInstanceOfTheApplication

boolkeys[256];//ArrayUsedForTheKeyboardRoutine
boolactive=TRUE;//WindowActiveFlagSetToTRUEByDefault
boolfullscreen=TRUE;//FullscreenFlagSetToFullscreenModeByDefault

LRESULTCALLBACKWndProc(HWND,UINT,WPARAM,LPARAM);//DeclarationForWndProc

GLvoidReSizeGLScene(GLsizeiwidth,GLsizeiheight)//ResizeAndInitializeTheGLWindow
{
if(height==0)//PreventADivideByZeroBy
{
height=1;//MakingHeightEqualOne
}

glViewport(0,0,width,height);//ResetTheCurrentViewport

glMatrixMode(GL_PROJECTION);//SelectTheProjectionMatrix
glLoadIdentity();//ResetTheProjectionMatrix

//CalculateTheAspectRatioOfTheWindow
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

glMatrixMode(GL_MODELVIEW);//SelectTheModelviewMatrix
glLoadIdentity();//ResetTheModelviewMatrix
}

intInitGL(GLvoid)//AllSetupForOpenGLGoesHere
{
glShadeModel(GL_SMOOTH);//EnableSmoothShading
glClearColor(0.0f,0.0f,0.0f,0.5f);//BlackBackground
glClearDepth(1.0f);//DepthBufferSetup
glEnable(GL_DEPTH_TEST);//EnablesDepthTesting
glDepthFunc(GL_LEQUAL);//TheTypeOfDepthTestingToDo
glHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_NICEST);//ReallyNicePerspectiveCalculations
returnTRUE;//InitializationWentOK
}

intDrawGLScene(GLvoid)//Here'sWhereWeDoAllTheDrawing
{
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);//ClearScreenAndDepthBuffer
glLoadIdentity();//ResetTheCurrentModelviewMatrix
returnTRUE;//EverythingWentOK
}

GLvoidKillGLWindow(GLvoid)//ProperlyKillTheWindow
{
if(fullscreen)//AreWeInFullscreenMode?
{
ChangeDisplaySettings(NULL,0);//IfSoSwitchBackToTheDesktop
ShowCursor(TRUE);//ShowMousePointer
}

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
}
}

/**//*ThisCodeCreatesOurOpenGLWindow.ParametersAre:*
*title-TitleToAppearAtTheTopOfTheWindow*
*width-WidthOfTheGLWindowOrFullscreenMode*
*height-HeightOfTheGLWindowOrFullscreenMode*
*bits-NumberOfBitsToUseForColor(8/16/24/32)*
*fullscreenflag-UseFullscreenMode(TRUE)OrWindowedMode(FALSE)*/

BOOLCreateGLWindow(char*title,intwidth,intheight,intbits,boolfullscreenflag)
{
GLuintPixelFormat;//HoldsTheResultsAfterSearchingForAMatch
WNDCLASSwc;//WindowsClassStructure
DWORDdwExStyle;//WindowExtendedStyle
DWORDdwStyle;//WindowStyle
RECTWindowRect;//GrabsRectangleUpperLeft/LowerRightValues
WindowRect.left=(long)0;//SetLeftValueTo0
WindowRect.right=(long)width;//SetRightValueToRequestedWidth
WindowRect.top=(long)0;//SetTopValueTo0
WindowRect.bottom=(long)height;//SetBottomValueToRequestedHeight

fullscreen=fullscreenflag;//SetTheGlobalFullscreenFlag

hInstance=GetModuleHandle(NULL);//GrabAnInstanceForOurWindow
wc.style=CS_HREDRAW|CS_VREDRAW|CS_OWNDC;//RedrawOnSize,AndOwnDCForWindow.
wc.lpfnWndProc=(WNDPROC)WndProc;//WndProcHandlesMessages
wc.cbClsExtra=0;//NoExtraWindowData
wc.cbWndExtra=0;//NoExtraWindowData
wc.hInstance=hInstance;//SetTheInstance
wc.hIcon=LoadIcon(NULL,IDI_WINLOGO);//LoadTheDefaultIcon
wc.hCursor=LoadCursor(NULL,IDC_ARROW);//LoadTheArrowPointer
wc.hbrBackground=NULL;//NoBackgroundRequiredForGL
wc.lpszMenuName=NULL;//WeDon'tWantAMenu
wc.lpszClassName="OpenGL";//SetTheClassName

if(!RegisterClass(&wc))//AttemptToRegisterTheWindowClass
{
MessageBox(NULL,"FailedToRegisterTheWindowClass.","ERROR",MB_OK|MB_ICONEXCLAMATION);
returnFALSE;//ReturnFALSE
}

if(fullscreen)//AttemptFullscreenMode?
{
DEVMODEdmScreenSettings;//DeviceMode
memset(&dmScreenSettings,0,sizeof(dmScreenSettings));//MakesSureMemory'sCleared
dmScreenSettings.dmSize=sizeof(dmScreenSettings);//SizeOfTheDevmodeStructure
dmScreenSettings.dmPelsWidth=width;//SelectedScreenWidth
dmScreenSettings.dmPelsHeight=height;//SelectedScreenHeight
dmScreenSettings.dmBitsPerPel=bits;//SelectedBitsPerPixel
dmScreenSettings.dmFields=DM_BITSPERPEL|DM_PELSWIDTH|DM_PELSHEIGHT;

//TryToSetSelectedModeAndGetResults.NOTE:CDS_FULLSCREENGetsRidOfStartBar.
if(ChangeDisplaySettings(&dmScreenSettings,CDS_FULLSCREEN)!=DISP_CHANGE_SUCCESSFUL)
{
//IfTheModeFails,OfferTwoOptions.QuitOrUseWindowedMode.
if(MessageBox(NULL,"TheRequestedFullscreenModeIsNotSupportedBy/nYourVideoCard.UseWindowedModeInstead?","NeHeGL",MB_YESNO|MB_ICONEXCLAMATION)==IDYES)
{
fullscreen=FALSE;//WindowedModeSelected.Fullscreen=FALSE
}
else
{
//PopUpAMessageBoxLettingUserKnowTheProgramIsClosing.
MessageBox(NULL,"ProgramWillNowClose.","ERROR",MB_OK|MB_ICONSTOP);
returnFALSE;//ReturnFALSE
}
}
}

if(fullscreen)//AreWeStillInFullscreenMode?
{
dwExStyle=WS_EX_APPWINDOW;//WindowExtendedStyle
dwStyle=WS_POPUP;//WindowsStyle
ShowCursor(FALSE);//HideMousePointer
}
else
{
dwExStyle=WS_EX_APPWINDOW|WS_EX_WINDOWEDGE;//WindowExtendedStyle
dwStyle=WS_OVERLAPPEDWINDOW;//WindowsStyle
}

AdjustWindowRectEx(&WindowRect,dwStyle,FALSE,dwExStyle);//AdjustWindowToTrueRequestedSize

//CreateTheWindow
if(!(hWnd=CreateWindowEx(dwExStyle,//ExtendedStyleForTheWindow
"OpenGL",//ClassName
title,//WindowTitle
dwStyle|//DefinedWindowStyle
WS_CLIPSIBLINGS|//RequiredWindowStyle
WS_CLIPCHILDREN,//RequiredWindowStyle
0,0,//WindowPosition
WindowRect.right-WindowRect.left,//CalculateWindowWidth
WindowRect.bottom-WindowRect.top,//CalculateWindowHeight
NULL,//NoParentWindow
NULL,//NoMenu
hInstance,//Instance
NULL)))//DontPassAnythingToWM_CREATE
{
KillGLWindow();//ResetTheDisplay
MessageBox(NULL,"WindowCreationError.","ERROR",MB_OK|MB_ICONEXCLAMATION);
returnFALSE;//ReturnFALSE
}

staticPIXELFORMATDESCRIPTORpfd=//pfdTellsWindowsHowWeWantThingsToBe
{
sizeof(PIXELFORMATDESCRIPTOR),//SizeOfThisPixelFormatDescriptor
1,//VersionNumber
PFD_DRAW_TO_WINDOW|//FormatMustSupportWindow
PFD_SUPPORT_OPENGL|//FormatMustSupportOpenGL
PFD_DOUBLEBUFFER,//MustSupportDoubleBuffering
PFD_TYPE_RGBA,//RequestAnRGBAFormat
bits,//SelectOurColorDepth
0,0,0,0,0,0,//ColorBitsIgnored
0,//NoAlphaBuffer
0,//ShiftBitIgnored
0,//NoAccumulationBuffer
0,0,0,0,//AccumulationBitsIgnored
16,//16BitZ-Buffer(DepthBuffer)
0,//NoStencilBuffer
0,//NoAuxiliaryBuffer
PFD_MAIN_PLANE,//MainDrawingLayer
0,//Reserved
0,0,0//LayerMasksIgnored
};

if(!(hDC=GetDC(hWnd)))//DidWeGetADeviceContext?
{
KillGLWindow();//ResetTheDisplay
MessageBox(NULL,"Can'tCreateAGLDeviceContext.","ERROR",MB_OK|MB_ICONEXCLAMATION);
returnFALSE;//ReturnFALSE
}

if(!(PixelFormat=ChoosePixelFormat(hDC,&pfd)))//DidWindowsFindAMatchingPixelFormat?
{
KillGLWindow();//ResetTheDisplay
MessageBox(NULL,"Can'tFindASuitablePixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
returnFALSE;//ReturnFALSE
}

if(!SetPixelFormat(hDC,PixelFormat,&pfd))//AreWeAbleToSetThePixelFormat?
{
KillGLWindow();//ResetTheDisplay
MessageBox(NULL,"Can'tSetThePixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
returnFALSE;//ReturnFALSE
}

if(!(hRC=wglCreateContext(hDC)))//AreWeAbleToGetARenderingContext?
{
KillGLWindow();//ResetTheDisplay
MessageBox(NULL,"Can'tCreateAGLRenderingContext.","ERROR",MB_OK|MB_ICONEXCLAMATION);
returnFALSE;//ReturnFALSE
}

if(!wglMakeCurrent(hDC,hRC))//TryToActivateTheRenderingContext
{
KillGLWindow();//ResetTheDisplay
MessageBox(NULL,"Can'tActivateTheGLRenderingContext.","ERROR",MB_OK|MB_ICONEXCLAMATION);
returnFALSE;//ReturnFALSE
}

ShowWindow(hWnd,SW_SHOW);//ShowTheWindow
SetForegroundWindow(hWnd);//SlightlyHigherPriority
SetFocus(hWnd);//SetsKeyboardFocusToTheWindow
ReSizeGLScene(width,height);//SetUpOurPerspectiveGLScreen

if(!InitGL())//InitializeOurNewlyCreatedGLWindow
{
KillGLWindow();//ResetTheDisplay
MessageBox(NULL,"InitializationFailed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
returnFALSE;//ReturnFALSE
}

returnTRUE;//Success
}

LRESULTCALLBACKWndProc(HWNDhWnd,//HandleForThisWindow
UINTuMsg,//MessageForThisWindow
WPARAMwParam,//AdditionalMessageInformation
LPARAMlParam)//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);//SendAQuitMessage
return0;//JumpBack
}

caseWM_KEYDOWN://IsAKeyBeingHeldDown?
{
keys[wParam]=TRUE;//IfSo,MarkItAsTRUE
return0;//JumpBack
}

caseWM_KEYUP://HasAKeyBeenReleased?
{
keys[wParam]=FALSE;//IfSo,MarkItAsFALSE
return0;//JumpBack
}

caseWM_SIZE://ResizeTheOpenGLWindow
{
ReSizeGLScene(LOWORD(lParam),HIWORD(lParam));//LoWord=Width,HiWord=Height
return0;//JumpBack
}
}

//PassAllUnhandledMessagesToDefWindowProc
returnDefWindowProc(hWnd,uMsg,wParam,lParam);
}

intWINAPIWinMain(HINSTANCEhInstance,//Instance
HINSTANCEhPrevInstance,//PreviousInstance
LPSTRlpCmdLine,//CommandLineParameters
intnCmdShow)//WindowShowState
{
MSGmsg;//WindowsMessageStructure
BOOLdone=FALSE;//BoolVariableToExitLoop

//AskTheUserWhichScreenModeTheyPrefer
if(MessageBox(NULL,"WouldYouLikeToRunInFullscreenMode?","StartFullScreen?",MB_YESNO|MB_ICONQUESTION)==IDNO)
{
fullscreen=FALSE;//WindowedMode
}

//CreateOurOpenGLWindow
if(!CreateGLWindow("NeHe'sOpenGLFramework",640,480,16,fullscreen))
{
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);//TranslateTheMessage
DispatchMessage(&msg);//DispatchTheMessage
}
}
else//IfThereAreNoMessages
{
//DrawTheScene.WatchForESCKeyAndQuitMessagesFromDrawGLScene()
if(active)//ProgramActive?
{
if(keys[VK_ESCAPE])//WasESCPressed?
{
done=TRUE;//ESCSignalledAQuit
}
else//NotTimeToQuit,UpdateScreen
{
DrawGLScene();//DrawTheScene
SwapBuffers(hDC);//SwapBuffers(DoubleBuffering)
}
}

if(keys[VK_F1])//IsF1BeingPressed?
{
keys[VK_F1]=FALSE;//IfSoMakeKeyFALSE
KillGLWindow();//KillOurCurrentWindow
fullscreen=!fullscreen;//ToggleFullscreen/WindowedMode
//RecreateOurOpenGLWindow
if(!CreateGLWindow("NeHe'sOpenGLFramework",640,480,16,fullscreen))
{
return0;//QuitIfWindowWasNotCreated
}
}
}
}

//Shutdown
KillGLWindow();//KillTheWindow
return(msg.wParam);//ExitTheProgram
}