NeHe教程：OpenGL进阶指南

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NeHeTutorials是一套由Andreas Lagotzki编译自英文原版的OpenGL教程，该系列教程发布于2004年12月。这些教程是将NeHe网站上的在线OpenGL教程转换成了RTF和PDF格式，适合双面打印在A4纸张上，旨在帮助学习者系统地掌握OpenGL编程。以下是部分内容概览： 1. **设置OpenGL环境**：教程首先指导读者如何在不同的操作系统上配置OpenGL，包括MacOS、Solaris以及MacOS X上使用GLUT库进行窗口设置。 2. **基本操作**：从"Your First Polygon"开始，介绍了如何绘制二维和三维图形的基本元素，如创建第一个多边形，并逐步添加颜色和变换功能。 3. **高级特性**：随后章节涉及更复杂的技术，如纹理映射，通过纹理过滤、光照效果和键盘控制实现三维物体的动态表现。接着探讨了混合模式（blending）、3D空间中的位图移动以及3D世界导航。 4. **特殊效果**：如“Flag Effect”（动态波浪纹理）展示了高级渲染技术，而“Display Lists”则讲解了列表化绘制以提高性能。此外，还涵盖了字体处理，如位图字体、轮廓字体和纹理映射轮廓字体。 5. **视觉增强**：包括了酷炫的雾效果，以及2D纹理字体和四元体（quadrics）的应用，为渲染增添了更多维度。 6. **粒子系统与动画**：“Particle Engine Using Triangle Strips”展示了如何利用三角形链表实现粒子系统的动画效果。 7. **遮罩与增强功能**：学习者可以在这里了解到线条渲染、抗锯齿、计时、透视视图和简单的音频应用，以及多纹理贴图和扩展功能。 8. **高级技术**：包括球面映射、多纹理及硬件扩展，如介绍如何加载对象文件和使用剪裁测试与TGA加载。 9. **变形与交互**："Morphing & Loading Objects From A File"教导如何实现形状的变形，以及从文件中加载对象以增强用户交互。 10. **复杂场景处理**：最后部分涵盖了剪辑与反射技术，以及如何结合tokens、扩展和Scissor Testing等技术，为更复杂的3D场景提供深度处理。 NeHeTutorials是一套详尽且实用的OpenGL教程，从基础入门到高级技术，覆盖了丰富的实践案例和理论知识，对学习OpenGL编程具有很高的参考价值。无论是对初学者还是进阶开发者，这套教程都是宝贵的学习资源。

16 Setting Up An OpenGL Window NeHe's OpenGL Tutorials

using fullscreen? How do I change the Window's title? How do I change the resolution or pixel format of the

Window? The following code does all of that! Therefore it's better learning material and will make writing

OpenGL programs of your own a lot easier!

As you can see the procedure returns BOOL (TRUE or FALSE), it also takes 5 parameters: title of the

Window, width of the Window, height of the Window, bits (16/24/32), and finally fullscreenflag TRUE for

fullscreen or FALSE for windowed. We return a boolean value that will tell us if the Window was created

successfully.

BOOL CreateGLWindow(char* title, int width, int height, int bits, bool fullscreenflag)

{

When we ask Windows to find us a pixel format that matches the one we want, the number of the mode that

Windows ends up finding for us will be stored in the variable PixelFormat.

GLuint PixelFormat; // Holds The Results After Searching For A Match

wc will be used to hold our Window Class structure. The Window Class structure holds information about

our window. By changing different fields in the Class we can change how the window looks and behaves.

Every window belongs to a Window Class. Before you create a window, you MUST register a Class for the

window.

WNDCLASS wc; // Windows Class Structure

dwExStyle and dwStyle will store the Extended and normal Window Style Information. I use variables to

store the styles so that I can change the styles depending on what type of window I need to create (A popup

window for fullscreen or a window with a border for windowed mode)

DWORD dwExStyle; // Window Extended Style

DWORD dwStyle; // Window Style

The following 5 lines of code grab the upper left, and lower right values of a rectangle. We'll use these

values to adjust our window so that the area we draw on is the exact resolution we want. Normally if we

create a 640x480 window, the borders of the window take up some of our resolution.

RECT WindowRect; // Grabs Rectangle Upper Left / Lower Right Values

WindowRect.left=(long)0; // Set Left Value To 0

WindowRect.right=(long)width; // Set Right Value To Requested Width

WindowRect.top=(long)0; // Set Top Value To 0

WindowRect.bottom=(long)height; // Set Bottom Value To Requested Height

In the next line of code we make the global variable fullscreen equal fullscreenflag.

fullscreen=fullscreenflag; // Set The Global Fullscreen Flag

In the next section of code, we grab an instance for our Window, then we declare the Window Class.

The style CS_HREDRAW and CS_VREDRAW force the Window to redraw whenever it is resized.

CS_OWNDC creates a private DC for the Window. Meaning the DC is not shared across applications.

WndProc is the procedure that watches for messages in our program. No extra Window data is used so we

zero the two fields. Then we set the instance. Next we set hIcon to NULL meaning we don't want an ICON

in the Window, and for a mouse pointer we use the standard arrow. The background color doesn't matter

(we set that in GL). We don't want a menu in this Window so we set it to NULL, and the class name can be

any name you want. I'll use "OpenGL" for simplicity.

// Grab An Instance For Our Window

hInstance = GetModuleHandle(NULL);

// Redraw On Move, And Own DC For Window

wc.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;

wc.lpfnWndProc = (WNDPROC) WndProc; // WndProc Handles Messages

NeHe's OpenGL Tutorials Setting Up An OpenGL Window 17

wc.cbClsExtra = 0; // No Extra Window Data

wc.cbWndExtra = 0; // No Extra Window Data

wc.hInstance = hInstance; // Set The Instance

wc.hIcon = LoadIcon(NULL, IDI_WINLOGO); // Load The Default Icon

wc.hCursor = LoadCursor(NULL, IDC_ARROW); // Load The Arrow Pointer

wc.hbrBackground = NULL; // No Background Required For GL

wc.lpszMenuName = NULL; // We Don't Want A Menu

wc.lpszClassName = "OpenGL"; // Set The Class Name

Now we register the Class. If anything goes wrong, an error message will pop up. Clicking on OK in the

error box will exit the program.

if (!RegisterClass(&wc)) // Attempt To Register The Window Class

{

MessageBox(NULL,"Failed To Register The Window Class.","ERROR",

MB_OK|MB_ICONEXCLAMATION);

return FALSE; // Exit And Return FALSE

}

Now we check to see if the program should run in fullscreen mode or windowed mode. If it should be

fullscreen mode, we'll attempt to set fullscreen mode.

if (fullscreen) // Attempt Fullscreen Mode?

{

The next section of code is something people seem to have a lot of problems with... switching to fullscreen

mode. There are a few very important things you should keep in mind when switching to full screen mode.

Make sure the width and height that you use in fullscreen mode is the same as the width and height you

plan to use for your window, and most importantly, set fullscreen mode BEFORE you create your window. In

this code, you don't have to worry about the width and height, the fullscreen and the window size are both

set to be the size requested.

DEVMODE dmScreenSettings; // Device Mode

// Makes Sure Memory's Cleared

memset(&dmScreenSettings,0,sizeof(dmScreenSettings));

// Size Of The Devmode Structure

dmScreenSettings.dmSize=sizeof(dmScreenSettings);

dmScreenSettings.dmPelsWidth = width; // Selected Screen Width

dmScreenSettings.dmPelsHeight = height; // Selected Screen Height

dmScreenSettings.dmBitsPerPel = bits; // Selected Bits Per Pixel

dmScreenSettings.dmFields=DM_BITSPERPEL|DM_PELSWIDTH|DM_PELSHEIGHT;

In the code above we clear room to store our video settings. We set the width, height and bits that we want

the screen to switch to. In the code below we try to set the requested full screen mode. We stored all the

information about the width, height and bits in dmScreenSettings. In the line below ChangeDisplaySettings

tries to switch to a mode that matches what we stored in dmScreenSettings. I use the parameter

CDS_FULLSCREEN when switching modes, because it's supposed to remove the start bar at the bottom of

the screen, plus it doesn't move or resize the windows on your desktop when you switch to fullscreen mode

and back.

// Try To Set Selected Mode And Get Results.

// NOTE: CDS_FULLSCREEN Gets Rid Of Start Bar.

if ( ChangeDisplaySettings( &dmScreenSettings,CDS_FULLSCREEN)

!= DISP_CHANGE_SUCCESSFUL)

{

If the mode couldn't be set the code below will run. If a matching fullscreen mode doesn't exist, a message

box will pop up offering two options: The option to run in a window or the option to quit.

// If The Mode Fails, Offer Two Options. Quit Or Run In A Window.

if ( MessageBox( NULL, "The Requested Fullscreen Mode Is Not "

"Supported By\nYour Video Card. Use Windowed Mode Instead?",

18 Setting Up An OpenGL Window NeHe's OpenGL Tutorials

"NeHe GL", MB_YESNO|MB_ICONEXCLAMATION) == IDYES )

{

If the user decided to use windowed mode, the variable fullscreen becomes FALSE, and the program

continues running.

fullscreen=FALSE; // Select Windowed Mode (Fullscreen=FALSE)

}

else

{

If the user decided to quit, a message box will pop up telling the user that the program is about to close.

FALSE will be returned telling our program that the window was not created successfully. The program will

then quit.

// Pop Up A Message Box Letting User Know The Program Is Closing.

MessageBox(NULL,"Program Will Now Close.","ERROR",

MB_OK|MB_ICONSTOP);

return FALSE; // Exit And Return FALSE

}

Because the fullscreen code above may have failed and the user may have decided to run the program in a

window instead, we check once again to see if fullscreen is TRUE or FALSE before we set up the screen /

window type.

if (fullscreen) // Are We Still In Fullscreen Mode?

{

If we are still in fullscreen mode we'll set the extended style to WS_EX_APPWINDOW, which force a top

level window down to the taskbar once our window is visible. For the window style we'll create a

WS_POPUP window. This type of window has no border around it, making it perfect for fullscreen mode.

Finally, we disable the mouse pointer. If your program is not interactive, it's usually nice to disable the

mouse pointer when in fullscreen mode. It's up to you though.

dwExStyle=WS_EX_APPWINDOW; // Window Extended Style

dwStyle=WS_POPUP; // Windows Style

ShowCursor(FALSE); // Hide Mouse Pointer

}

else

{

If we're using a window instead of fullscreen mode, we'll add WS_EX_WINDOWEDGE to the extended

style. This gives the window a more 3D look. For style we'll use WS_OVERLAPPEDWINDOW instead of

WS_POPUP. WS_OVERLAPPEDWINDOW creates a window with a title bar, sizing border, window menu,

and minimize / maximize buttons.

dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE; // Window Extended Style

dwStyle=WS_OVERLAPPEDWINDOW; // Windows Style

}

The line below adjust our window depending on what style of window we are creating. The adjustment will

make our window exactly the resolution we request. Normally the borders will overlap parts of our window.

By using the AdjustWindowRectEx command none of our OpenGL scene will be covered up by the borders,

instead, the window will be made larger to account for the pixels needed to draw the window border. In

fullscreen mode, this command has no effect.

// Adjust Window To True Requested Size

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

NeHe's OpenGL Tutorials Setting Up An OpenGL Window 19

In the next section of code, we're going to create our window and check to see if it was created properly.

We pass CreateWindowEx() all the parameters it requires. The extended style we decided to use. The class

name (which has to be the same as the name you used when you registered the Window Class). The

window title. The window style. The top left position of your window (0,0 is a safe bet). The width and height

of the window. We don't want a parent window, and we don't want a menu so we set both these parameters

to NULL. We pass our window instance, and finally we NULL the last parameter.

Notice we include the styles WS_CLIPSIBLINGS and WS_CLIPCHILDREN along with the style of window

we've decided to use. WS_CLIPSIBLINGS and WS_CLIPCHILDREN are both REQUIRED for OpenGL to

work properly. These styles prevent other windows from drawing over or into our OpenGL Window.

if (!(hWnd=CreateWindowEx(

dwExStyle, // Extended Style For The Window

"OpenGL", // Class Name

title, // Window Title

WS_CLIPSIBLINGS | // Required Window Style

WS_CLIPCHILDREN | // Required Window Style

dwStyle, // Selected Window Style

0, 0, // Window Position

WindowRect.right-WindowRect.left, // Calculate Adjusted Window Width

WindowRect.bottom-WindowRect.top, // Calculate Adjusted Window Height

NULL, // No Parent Window

NULL, // No Menu

hInstance, // Instance

NULL // Don't Pass Anything To WM_CREATE

)))

Next we check to see if our window was created properly. If our window was created, hWnd will hold the

window handle. If the window wasn't created the code below will pop up an error message and the program

will quit.

{

KillGLWindow(); // Reset The Display

MessageBox(NULL,"Window Creation Error.","ERROR", MB_OK|MB_ICONEXCLAMATION);

return FALSE; // Return FALSE

}

The next section of code describes a Pixel Format. We choose a format that supports OpenGL and double

buffering, along with RGBA (red, green, blue, alpha channel). We try to find a pixel format that matches the

bits we decided on (16bit,24bit,32bit). Finally we set up a 16bit Z-Buffer. The remaining parameters are

either not used or are not important (aside from the stencil buffer and the (slow) accumulation buffer).

// pfd Tells Windows How We Want Things To Be

static PIXELFORMATDESCRIPTOR pfd =

{

sizeof(PIXELFORMATDESCRIPTOR), // Size Of This Pixel Format Descriptor

1, // Version Number

PFD_DRAW_TO_WINDOW | // Format Must Support Window

PFD_SUPPORT_OPENGL | // Format Must Support OpenGL

PFD_DOUBLEBUFFER, // Must Support Double Buffering

PFD_TYPE_RGBA, // Request An RGBA Format

bits, // Select Our Color Depth

0, 0, 0, 0, 0, 0, // Color Bits Ignored

0, // No Alpha Buffer

0, // Shift Bit Ignored

0, // No Accumulation Buffer

0, 0, 0, 0, // Accumulation Bits Ignored

16, // 16Bit Z-Buffer (Depth Buffer)

0, // No Stencil Buffer

0, // No Auxiliary Buffer

PFD_MAIN_PLANE, // Main Drawing Layer

0, // Reserved

0, 0, 0 // Layer Masks Ignored

};

20 Setting Up An OpenGL Window NeHe's OpenGL Tutorials

If there were no errors while creating the window, we'll attempt to get an OpenGL Device Context. If we

can't get a DC an error message will pop onto the screen, and the program will quit (return FALSE).

if (!(hDC=GetDC(hWnd))) // Did We Get A Device Context?

{

KillGLWindow(); // Reset The Display

MessageBox(NULL,"Can't Create A GL Device Context.","ERROR",

MB_OK|MB_ICONEXCLAMATION);

return FALSE; // Return FALSE

}

If we managed to get a Device Context for our OpenGL window we'll try to find a pixel format that matches

the one we described above. If Windows can't find a matching pixel format, an error message will pop onto

the screen and the program will quit (return FALSE).

// Did Windows Find A Matching Pixel Format?

if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd)))

{

KillGLWindow(); // Reset The Display

MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",

MB_OK|MB_ICONEXCLAMATION);

return FALSE; // Return FALSE

}

If windows found a matching pixel format we'll try setting the pixel format. If the pixel format cannot be set,

an error message will pop up on the screen and the program will quit (return FALSE).

// Are We Able To Set The Pixel Format?

if(!SetPixelFormat(hDC,PixelFormat,&pfd))

{

KillGLWindow(); // Reset The Display

MessageBox(NULL,"Can't Set The PixelFormat.","ERROR",

MB_OK|MB_ICONEXCLAMATION);

return FALSE; // Return FALSE

}

If the pixel format was set properly we'll try to get a Rendering Context. If we can't get a Rendering Context

an error message will be displayed on the screen and the program will quit (return FALSE).

// Are We Able To Get A Rendering Context?

if (!(hRC=wglCreateContext(hDC)))

{

KillGLWindow(); // Reset The Display

MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",

MB_OK|MB_ICONEXCLAMATION);

return FALSE; // Return FALSE

}

If there have been no errors so far, and we've managed to create both a Device Context and a Rendering

Context all we have to do now is make the Rendering Context active. If we can't make the Rendering

Context active an error message will pop up on the screen and the program will quit (return FALSE).

if(!wglMakeCurrent(hDC,hRC)) // Try To Activate The Rendering Context

{

KillGLWindow(); // Reset The Display

MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",

MB_OK|MB_ICONEXCLAMATION);

return FALSE; // Return FALSE

}

If everything went smoothly, and our OpenGL window was created we'll show the window, set it to be the

foreground window (giving it more priority) and then set the focus to that window. Then we'll call

ReSizeGLScene passing the screen width and height to set up our perspective OpenGL screen.

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