OPENGL4_变换

几种变换的几何意义说明

http://blog.csdn.net/onafioo/article/details/22094247

变换的执行顺序问题

正常顺序

1 视图（观察）变换

2 模型变换

3 投影变换

4 视口变换

变换相关OpenGL函数说明

glViewport(GLint x,GLint y,GLsizei width,GLsizei height)

设置视口

glMatrixMode (GLenum mode)

指定哪一个矩阵堆栈是下一个矩阵操作的目标

可选值

GL_MODELVIEW,对模型视景矩阵堆栈应用随后的矩阵操作.

GL_PROJECTION,对投影矩阵应用随后的矩阵操作.

GL_TEXTURE,对纹理矩阵堆栈应用随后的矩阵操作.

glLoadIdentity();

清空glMatrixMode 指定的类型的矩阵(变成单位矩阵)，相当于复位

gluPerspective(GLdouble fovy,GLdouble aspect,GLdouble zNear,GLdouble zFar)

设置视景体，在glMatrixMode(GL_PROJECTION)下使用

fovy：视角

aspect：屏幕纵宽比

zNear：近裁剪面z值

zFar：远裁剪面z值

gluLookAt(GLdoble eyex,GLdouble eyey,GLdouble eyez,GLdouble centerx,GLdouble centery,GLdouble centerz,GLdouble upx,GLdouble upy,GLdouble upz);

设置摄像机朝向

9个参数分别代表，摄像机位置xyz，摄像机看向的目标位置xyz，摄像机朝向xyz（摄像机和这个向量的关系类似人眼和人站立的方向），一般设置为（0，1，0），代表人正常站立，眼睛朝前看

glTranslatef (GLfloat x, GLfloat y, GLfloat z);

平移

glScalef (GLfloat x, GLfloat y, GLfloat z);

缩放

glRotatef (GLfloat angle, GLfloat x, GLfloat y, GLfloat z)

angle：旋转角度

xyz：旋转轴

代码中几种变换出现的顺序

//视口变换

glViewport(0,0,width,height);

//投影变换

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

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

//模型视图变换

glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

//摄像机位置，观察点，摄像机方位

gluLookAt();

后面跟模型变换的平移，旋转，缩放

原因

Opengl让矩阵和顶点做左乘操作

例如C*B*A*v，实际是先乘A矩阵，然后B，然后C，所以变换顺序上，代码出现的顺序是反序。

所以下面代码意思为，先缩放，在旋转，然后再移动（下面代码在执行前已经）

glLoadIdentity();//清空模型观察矩阵（之前已经执行了glMatrixMode(GL_MODELVIEW)切换到了模型观察矩阵，并且已经对矩阵做过平移旋转等操作，所以要清空）

glTranslatef(8.0f,0.0f,-18.9f);//移动
glRotatef(rotateAngle,0.0f,1.0f,0.0f);//旋转
glScalef(1.5f,1.5f,1.5f);//缩放

glBegin(GL_TRIANGLES);
glColor3f(1.0f,0.0f,1.0f);// 设置当前色为紫色
glVertex3f( 0.0f, 1.0f, 0.0f);//对象绕自身的轴旋转，必须让对象的中心坐标总是(0.0f,0,0f,0,0f)
glVertex3f(-1.0f,-1.0f, 0.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
rotateAngle+=0.1;
glEnd();

完整代码及效果

#include "stdafx.h"
#include "Nehe_Base.h"

#include "GL.H"				// Header File For The OpenGL32 Library
#include "GLU.H"			// Header File For The GLu32 Library
#include "GLAUX.H"			// Header File For The Glaux Library

HDC			hDC=NULL;		// Private GDI Device Context
HGLRC		hRC=NULL;		// Permanent Rendering Context
HWND		hWnd=NULL;		// Holds Our Window Handle
HINSTANCE	hInstance;		// Holds The Instance Of The Application

bool	keys[256];			// Array Used For The Keyboard Routine
bool	active=TRUE;		// Window Active Flag Set To TRUE By Default
bool	fullscreen=TRUE;	// Fullscreen Flag Set To Fullscreen Mode By Default

GLfloat rotateAngle;

LRESULT	CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);	// Declaration For WndProc

GLvoid ReSizeGLScene(GLsizei width, GLsizei height)		// Resize And Initialize The GL Window
{
	if (height==0)										// Prevent A Divide By Zero By
	{
		height=1;										// Making Height Equal One
	}

	glViewport(0,0,width,height);						// Reset The Current Viewport

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

	glMatrixMode(GL_MODELVIEW);							// Select The Modelview Matrix
	glLoadIdentity();									// Reset The Modelview Matrix

}

int InitGL(GLvoid)										// All Setup For OpenGL Goes Here
{
	glShadeModel(GL_SMOOTH);							// Enable Smooth Shading
	glClearColor(0.0f, 0.0f, 0.0f, 0.5f);				// Black Background
	glClearDepth(1.0f);									// Depth Buffer Setup
	glEnable(GL_DEPTH_TEST);							// Enables Depth Testing
	glDepthFunc(GL_LEQUAL);								// The Type Of Depth Testing To Do
	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);	// Really Nice Perspective Calculations
	return TRUE;										// Initialization Went OK
}

int DrawGLScene(GLvoid)									// Here's Where We Do All The Drawing
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	// Clear Screen And Depth Buffer
	glLoadIdentity();									// Reset The Current Modelview Matrix

	gluLookAt(0.0f,0.0f,10.0f,0.0f,0.0f,0.0f,0.0f,1.0f,0.0f);
	//移动是相对当前位置移动（第一次移动相对与屏幕中心0，0，0下一次再移动时相对的就是本次移动后的位置了）
	//向屏幕内移动18.9个单位，这样1个单位（1米）对应480/(2*tan(22.5)*(18.9+0.1)= 30像素
	glTranslatef(0.0f,0.0f,-18.9f);

	// 绘制不连续线段，把屏幕分成9部分
	glBegin(GL_LINES);
	glColor3f(1.0f,1.0f,1.0f);// 设置当前色为红色
	// 横线
	glVertex3f( -21.0f, 3.0f, 0.0f);
	glVertex3f(21.0f, 3.0f, 0.0f);
	glVertex3f( -21.0f, -3.0f, 0.0f);
	glVertex3f( 21.0f, -3.0f, 0.0f);
	// 竖线
	glVertex3f( -3.0f, 8.0f, 0.0f);
	glVertex3f(-3.0f, -8.0f, 0.0f);
	glVertex3f( 3.0f, 8.0f, 0.0f);
	glVertex3f( 3.0f, -8.0f, 0.0f);
	glEnd();

	// 绘制点
	glBegin(GL_POINTS);
	glColor3f(1.0f,0.0f,0.0f);// 设置当前色为红色
	glVertex3f( -8.0f, 5.5f, 0.0f);
	glVertex3f( -7.5f, 5.5f, 0.0f);
	glVertex3f( -7.0f, 5.5f, 0.0f);
	glEnd();

	// 绘制不闭合折线
	glBegin(GL_LINE_STRIP);
	glColor3f(1.0f,1.0f,0.0f);// 设置当前色为黄色
	glVertex3f( -2.0f, 5.5f, 0.0f);
	glVertex3f( 2.0f, 5.5f, 0.0f);
	glVertex3f( -2.0f, 4.0f, 0.0f);
	glVertex3f( 2.0f, 4.0f, 0.0f);
	glEnd();

	// 绘制闭合折线
	glBegin(GL_LINE_LOOP);
	glColor3f(0.0f,0.0f,1.0f);// 设置当前色为蓝色
	glVertex3f( 6.0f, 6.0f, 0.0f);
	glVertex3f( 4.0f, 4.0f, 0.0f);
	glVertex3f( 8.0f, 4.0f, 0.0f);
	glEnd();

	// 绘制多组独立填充三角形（以下绘制2个三角形）
	glBegin(GL_TRIANGLES);
	glColor3f(1.0f,0.0f,0.0f);// 设置当前色为红色
	glVertex3f( -9.0f, 1.0f, 0.0f);
	glVertex3f(-8.0f,-1.0f, 0.0f);
	glVertex3f( -10.0f,-1.0f, 0.0f);

	glVertex3f( -6.0f, 1.0f, 0.0f);
	glVertex3f(-5.0f,-1.0f, 0.0f);
	glVertex3f( -7.0f,-1.0f, 0.0f);
	glEnd();

	// 绘制三角形带
	glBegin(GL_TRIANGLE_STRIP);//(以下绘制3个连续三角形)
	//第一个三角形由点123逆时针构成
	//第二个三角形由点324逆时针构成
	//第三个三角形由点345逆时针构成
	glColor3f(1.0f,0.0f,0.0f);// 设置当前色为红色
	glVertex3f( -2.0f,-1.0f, 0.0f);//点1
	glVertex3f(0.0f,-1.0f, 0.0f);//点2
	glVertex3f( -1.0f, 1.0f, 0.0f);//点3
	glColor3f(0.0f,1.0f,0.0f);// 设置当前色为绿色
	glVertex3f( 1.0f,1.0f, 0.0f);//点4
	glColor3f(0.0f,0.0f,1.0f);// 设置当前色为蓝色
	glVertex3f(2.5f,2.5f, 0.0f);//点5
	glEnd();

	//旋转
	//glLoadIdentity();
	glTranslatef(0.0f,0.0f,18.9f);
	glTranslatef(8.0f,0.0f,-18.9f);
	glRotatef(rotateAngle,0.0f,1.0f,0.0f);
	//glScalef(1.5f,1.5f,1.5f);
	glBegin(GL_TRIANGLES);
	glColor3f(1.0f,0.0f,1.0f);// 设置当前色为紫色
	glVertex3f( 0.0f, 1.0f, 0.0f);
	glVertex3f(-1.0f,-1.0f, 0.0f);
	glVertex3f( 1.0f,-1.0f, 0.0f);
	rotateAngle+=0.1;
	glEnd();

	return TRUE;										// Everything Went OK
}

GLvoid KillGLWindow(GLvoid)								// Properly Kill The Window
{
	if (fullscreen)										// Are We In Fullscreen Mode?
	{
		ChangeDisplaySettings(NULL,0);					// If So Switch Back To The Desktop
		ShowCursor(TRUE);								// Show Mouse Pointer
	}

	if (hRC)											// Do We Have A Rendering Context?
	{
		if (!wglMakeCurrent(NULL,NULL))					// Are We Able To Release The DC And RC Contexts?
		{
			MessageBox(NULL,"Release Of DC And RC Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
		}

		if (!wglDeleteContext(hRC))						// Are We Able To Delete The RC?
		{
			MessageBox(NULL,"Release Rendering Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
		}
		hRC=NULL;										// Set RC To NULL
	}

	if (hDC && !ReleaseDC(hWnd,hDC))					// Are We Able To Release The DC
	{
		MessageBox(NULL,"Release Device Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
		hDC=NULL;										// Set DC To NULL
	}

	if (hWnd && !DestroyWindow(hWnd))					// Are We Able To Destroy The Window?
	{
		MessageBox(NULL,"Could Not Release hWnd.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
		hWnd=NULL;										// Set hWnd To NULL
	}

	if (!UnregisterClass("OpenGL",hInstance))			// Are We Able To Unregister Class
	{
		MessageBox(NULL,"Could Not Unregister Class.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
		hInstance=NULL;									// Set hInstance To NULL
	}
}

/*	This Code Creates Our OpenGL Window.  Parameters Are:					*
 *	title			- Title To Appear At The Top Of The Window				*
 *	width			- Width Of The GL Window Or Fullscreen Mode				*
 *	height			- Height Of The GL Window Or Fullscreen Mode			*
 *	bits			- Number Of Bits To Use For Color (8/16/24/32)			*
 *	fullscreenflag	- Use Fullscreen Mode (TRUE) Or Windowed Mode (FALSE)	*/

BOOL CreateGLWindow(char* title, int width, int height, int bits, bool fullscreenflag)
{
	//当我们要求Windows为我们寻找相匹配的象素格式时，Windows寻找结束后将模式值保存在变量PixelFormat中。
	GLuint		PixelFormat;			// Holds The Results After Searching For A Match

	WNDCLASS	wc;						// Windows Class Structure
	DWORD		dwExStyle;				// Window Extended Style
	DWORD		dwStyle;				// Window Style
	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

	fullscreen=fullscreenflag;			// Set The Global Fullscreen Flag

	hInstance			= GetModuleHandle(NULL);				// Grab An Instance For Our Window
	wc.style			= CS_HREDRAW | CS_VREDRAW | CS_OWNDC;	// Redraw On Size, And Own DC For Window.
	wc.lpfnWndProc		= (WNDPROC) WndProc;					// WndProc Handles Messages
	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

	if (!RegisterClass(&wc))									// Attempt To Register The Window Class
	{
		MessageBox(NULL,"Failed To Register The Window Class.","ERROR",MB_OK|MB_ICONEXCLAMATION);
		return FALSE;											// Return FALSE
	}

	if (fullscreen)												// Attempt Fullscreen Mode?
	{
		DEVMODE dmScreenSettings;								// Device Mode
		memset(&dmScreenSettings,0,sizeof(dmScreenSettings));	// Makes Sure Memory's Cleared
		dmScreenSettings.dmSize=sizeof(dmScreenSettings);		// Size Of The Devmode Structure
		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;

		// 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 Fails, Offer Two Options.  Quit Or Use Windowed Mode.
			if (MessageBox(NULL,"The Requested Fullscreen Mode Is Not Supported By\nYour Video Card. Use Windowed Mode Instead?","NeHe GL",MB_YESNO|MB_ICONEXCLAMATION)==IDYES)
			{
				fullscreen=FALSE;		// Windowed Mode Selected.  Fullscreen = FALSE
			}
			else
			{
				// 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;									// Return FALSE
			}
		}
	}

	if (fullscreen)												// Are We Still In Fullscreen Mode?
	{
		dwExStyle=WS_EX_APPWINDOW;								// Window Extended Style
		dwStyle=WS_POPUP;										// Windows Style
		ShowCursor(FALSE);										// Hide Mouse Pointer
	}
	else
	{
		dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;			// Window Extended Style
		dwStyle=WS_OVERLAPPEDWINDOW;							// Windows Style
	}

	AdjustWindowRectEx(&WindowRect, dwStyle, FALSE, dwExStyle);		// Adjust Window To True Requested Size

	// Create The Window
	if (!(hWnd=CreateWindowEx(	dwExStyle,							// Extended Style For The Window
								"OpenGL",							// Class Name
								title,								// Window Title
								dwStyle |							// Defined Window Style
								WS_CLIPSIBLINGS |					// Required Window Style
								WS_CLIPCHILDREN,					// Required Window Style
								0, 0,								// Window Position
								WindowRect.right-WindowRect.left,	// Calculate Window Width
								WindowRect.bottom-WindowRect.top,	// Calculate Window Height
								NULL,								// No Parent Window
								NULL,								// No Menu
								hInstance,							// Instance
								NULL)))								// Dont Pass Anything To WM_CREATE
	{
		KillGLWindow();								// Reset The Display
		MessageBox(NULL,"Window Creation Error.","ERROR",MB_OK|MB_ICONEXCLAMATION);
		return FALSE;								// Return FALSE
	}

	//像素格式明确了OpenGL绘制平面的特性，如象素缓冲区是单缓冲还是双缓冲，数据是 RGBA方式还是Color Index方式等。
	//每个OpenGL显示设备一般用名为PIXELFORMATDESCRIPTOR的结构来表示某个的像素格式
	static	PIXELFORMATDESCRIPTOR pfd=				// pfd Tells Windows How We Want Things To Be
	{
		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
	};

	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 (!(PixelFormat=ChoosePixelFormat(hDC,&pfd)))	// Did Windows Find A Matching Pixel Format?
	{
		KillGLWindow();								// Reset The Display
		MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
		return FALSE;								// Return FALSE
	}

	if(!SetPixelFormat(hDC,PixelFormat,&pfd))		// Are We Able To Set The Pixel Format?
	{
		KillGLWindow();								// Reset The Display
		MessageBox(NULL,"Can't Set The PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
		return FALSE;								// Return FALSE
	}

	if (!(hRC=wglCreateContext(hDC)))				// Are We Able To Get A Rendering Context?
	{
		KillGLWindow();								// Reset The Display
		MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
		return FALSE;								// 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
	}

	ShowWindow(hWnd,SW_SHOW);						// Show The Window
	SetForegroundWindow(hWnd);						// Slightly Higher Priority
	SetFocus(hWnd);									// Sets Keyboard Focus To The Window
	ReSizeGLScene(width, height);					// Set Up Our Perspective GL Screen

	if (!InitGL())									// Initialize Our Newly Created GL Window
	{
		KillGLWindow();								// Reset The Display
		MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
		return FALSE;								// Return FALSE
	}

	return TRUE;									// Success
}

LRESULT CALLBACK WndProc(	HWND	hWnd,			// Handle For This Window
							UINT	uMsg,			// Message For This Window
							WPARAM	wParam,			// Additional Message Information
							LPARAM	lParam)			// Additional Message Information
{
	switch (uMsg)									// Check For Windows Messages
	{
		case WM_ACTIVATE:							// Watch For Window Activate Message
		{
			if (!HIWORD(wParam))					// Check Minimization State
			{
				active=TRUE;						// Program Is Active
			}
			else
			{
				active=FALSE;						// Program Is No Longer Active
			}

			return 0;								// Return To The Message Loop
		}

		case WM_SYSCOMMAND:							// Intercept System Commands
		{
			switch (wParam)							// Check System Calls
			{
				case SC_SCREENSAVE:					// Screensaver Trying To Start?
				case SC_MONITORPOWER:				// Monitor Trying To Enter Powersave?
				return 0;							// Prevent From Happening
			}
			break;									// Exit
		}

		case WM_CLOSE:								// Did We Receive A Close Message?
		{
			PostQuitMessage(0);						// Send A Quit Message
			return 0;								// Jump Back
		}

		case WM_KEYDOWN:							// Is A Key Being Held Down?
		{
			keys[wParam] = TRUE;					// If So, Mark It As TRUE
			return 0;								// Jump Back
		}

		case WM_KEYUP:								// Has A Key Been Released?
		{
			keys[wParam] = FALSE;					// If So, Mark It As FALSE
			return 0;								// Jump Back
		}

		case WM_SIZE:								// Resize The OpenGL Window
		{
			ReSizeGLScene(LOWORD(lParam),HIWORD(lParam));  // LoWord=Width, HiWord=Height
			return 0;								// Jump Back
		}
	}

	// Pass All Unhandled Messages To DefWindowProc
	return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

int WINAPI WinMain(	HINSTANCE	hInstance,			// Instance
					HINSTANCE	hPrevInstance,		// Previous Instance
					LPSTR		lpCmdLine,			// Command Line Parameters
					int			nCmdShow)			// Window Show State
{
	MSG		msg;									// Windows Message Structure
	BOOL	done = FALSE;							// Bool Variable To Exit Loop

	// Ask The User Which Screen Mode They Prefer
	if (MessageBox(NULL,"Would You Like To Run In Fullscreen Mode?", "Start FullScreen?",MB_YESNO|MB_ICONQUESTION)==IDNO)
	{
		fullscreen = FALSE;							// Windowed Mode
	}

	// Create Our OpenGL Window
	if (!CreateGLWindow("NeHe's OpenGL Framework",640,480,16,fullscreen))
	{
		return 0;									// Quit If Window Was Not Created
	}

	while(!done)									// Loop That Runs While done=FALSE
	{
		if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))	// Is There A Message Waiting?
		{
			if (msg.message==WM_QUIT)				// Have We Received A Quit Message?
			{
				done=TRUE;							// If So done=TRUE
			}
			else									// If Not, Deal With Window Messages
			{
				TranslateMessage(&msg);				// Translate The Message
				DispatchMessage(&msg);				// Dispatch The Message
			}
		}
		else										// If There Are No Messages
		{
			// Draw The Scene.  Watch For ESC Key And Quit Messages From DrawGLScene()
			if (active)								// Program Active?
			{
				if (keys[VK_ESCAPE])				// Was ESC Pressed?
				{
					done=TRUE;						// ESC Signalled A Quit
				}
				else								// Not Time To Quit, Update Screen
				{
					DrawGLScene();					// Draw The Scene
					SwapBuffers(hDC);				// Swap Buffers (Double Buffering)
				}
			}

			if (keys[VK_F1])						// Is F1 Being Pressed?
			{
				keys[VK_F1]=FALSE;					// If So Make Key FALSE
				KillGLWindow();						// Kill Our Current Window
				fullscreen=!fullscreen;				// Toggle Fullscreen / Windowed Mode
				// Recreate Our OpenGL Window
				if (!CreateGLWindow("NeHe's OpenGL Framework",640,480,16,fullscreen))
				{
					return 0;						// Quit If Window Was Not Created
				}
			}
		}
	}

	// Shutdown
	KillGLWindow();									// Kill The Window
	return (msg.wParam);							// Exit The Program
}