第一篇笔记中的OpenGL框架其实很简单，大致有如下几个步骤：
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
#include <windows.h>#include <GL\gl.h>#include <GL\glu.h>#include <GL\glaux.h>HINSTANCE hInstance;//当前程序实例HDC hDC = NULL;//设备环境HGLRC hRC = NULL;//绘制环境HWND hWnd = NULL;//窗口句柄bool keys[256];bool active = TRUE;LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);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); // Select The Projection Matrix glLoadIdentity(); // Reset The Projection Matrix // Calculate The Aspect Ratio Of The Window 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(0.3f,0.0f, 0.5f, 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(); glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0 glBegin(GL_TRIANGLES); // Drawing Using Triangles glVertex3f( 0.0f, 1.0f, 0.0f); // Top glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right glEnd(); // Finished Drawing The Triangle glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units glBegin(GL_QUADS); // Draw A Quad glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left glEnd(); // Done Drawing The Quad// Reset The Current Modelview Matrix return TRUE; // Everything Went OK}GLvoid KillGLWindow(GLvoid) // Properly Kill The Window{ 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 }}BOOL CreateGLWindow(char* title,int width,int height,int bits){/**//* 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*/ GLuint PixelFormat; WNDCLASS wc; DWORD dwExStyle; DWORD dwStyle; RECT WindowRect; 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); return FALSE; } dwExStyle = WS_EX_APPWINDOW | WS_EX_WINDOWEDGE; dwStyle = WS_OVERLAPPEDWINDOW; AdjustWindowRectEx(&WindowRect,dwExStyle,FALSE,dwStyle); 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 { MessageBox(NULL,"创建窗口失败","ERROR",MB_OK|MB_ICONEXCLAMATION); return FALSE; } 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))) { KillGLWindow(); MessageBox(NULL,"无法创建GL设备环境.","ERROR",MB_OK|MB_ICONEXCLAMATION); return FALSE; } if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd))) // Did Windows Find A Matching Pixel Format? { KillGLWindow(); // Reset The Display MessageBox(NULL,"无法找到合适的像素格式.","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,"像素格式无法设置.","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,"无法创建一个绘制环境.","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,"无法激活绘制环境.","ERROR",MB_OK|MB_ICONEXCLAMATION); return FALSE; // Return FALSE } 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,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION); return FALSE;//返回 FALSE } return TRUE;}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,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nShowCmd){ MSG msg; // Windows Message Structure BOOL done=FALSE; // Bool Variable To Exit Loop // Create Our OpenGL Window if (!CreateGLWindow("NeHe's OpenGL Framework",640,480,16)) { 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) } } } } // Shutdown KillGLWindow(); // Kill The Window return (msg.wParam); // Exit The Program }
其中最核心的代码是：
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(); glTranslatef(-1.5f,0.0f,-6.0f); // Move Left 1.5 Units And Into The Screen 6.0 glBegin(GL_TRIANGLES); // Drawing Using Triangles glVertex3f( 0.0f, 1.0f, 0.0f); // Top glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right glEnd(); // Finished Drawing The Triangle glTranslatef(3.0f,0.0f,0.0f); // Move Right 3 Units glBegin(GL_QUADS); // Draw A Quad glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left glVertex3f( 1.0f, 1.0f, 0.0f); // Top Right glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left glEnd(); // Done Drawing The Quad// Reset The Current Modelview Matrix return TRUE; // Everything Went OK}
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0.0f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(0.0f)，最后移入屏幕6.0f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(-1.5f,0.0f,-6.0f); // 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(3.0f,0.0f,0.0f); // 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。
