开始使用 OpenGL
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本文介绍如何开始使用 OpenGL。
引言
本文介绍如何开始使用 OpenGL。
入门
- 启动 Visual Studio 并选择一个新的 Win32 应用程序项目，选择空项目，点击完成。
- 向您的项目添加一个名为 Main.cpp 的新文件。
- 转到 项目/设置/链接 选项卡，并在对象/库模块中输入 opengl32.lib 和 glu32.lib。
包含
#include <windows.h> #include <GL/gl.h> #include <GL/glu.h> LONG WINAPI WndProc(HWND,UINT,WPARAM,LPARAM);//Window procedure HGLRC SetUpOpenGL(HWND hwnd);//Initialize OpenGL void DrawOpenGLScene(void);//Actual Drawing code
您的 WinMain() 应该如下所示
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,
LPSTR lpCmdLine,int nCmdShow)
{
static char szAppName[] = "OpenGL";
static char szTitle[]="Getting Started With OpenGL";
WNDCLASS wc; // windows class sruct
MSG msg; // message struct
HWND hWnd; // Main window handle.
// Fill in window class structure with parameters that
// describe the main window.
wc.style =
CS_HREDRAW | CS_VREDRAW;// Class style(s).
wc.lpfnWndProc =
(WNDPROC)WndProc; // Window Procedure
wc.cbClsExtra = 0; // No per-class extra data.
wc.cbWndExtra = 0; // No per-window extra data.
wc.hInstance =
hInstance; // Owner of this class
wc.hIcon = NULL; // Icon name
wc.hCursor =
LoadCursor(NULL, IDC_ARROW);// Cursor
wc.hbrBackground =
(HBRUSH)(COLOR_WINDOW+1);// Default color
wc.lpszMenuName = NULL; // Menu from .RC
wc.lpszClassName =
szAppName; // Name to register as
// Register the window class
RegisterClass( &wc );
// Create a main window for this application instance.
hWnd = CreateWindow(
szAppName, // app name
szTitle, // Text for window title bar
WS_OVERLAPPEDWINDOW// Window style
// NEED THESE for OpenGL calls to work!
| WS_CLIPCHILDREN | WS_CLIPSIBLINGS,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0,
NULL, // no parent window
NULL, // Use the window class menu.
hInstance,// This instance owns this window
NULL // We don't use any extra data
);
// If window could not be created, return zero
if ( !hWnd )
{
return( 0 );
}
// Make the window visible & update its client area
ShowWindow( hWnd, 1 );// Show the window
UpdateWindow( hWnd ); // Sends WM_PAINT message
// Enter the Windows message loop
// Get and dispatch messages until WM_QUIT
while (GetMessage(&msg, // message structure
NULL, // handle of window receiving
// the message
0, // lowest message id to examine
0)) // highest message id to examine
{
TranslateMessage( &msg ); // Translates messages
DispatchMessage( &msg ); // then dispatches
}
return( msg.wParam );
}
您的窗口过程如下所示
LONG WINAPI WndProc( HWND hWnd, UINT msg,
WPARAM wParam, LPARAM lParam )
{
HDC hDC;
static HGLRC hRC; // Note this is STATIC!
PAINTSTRUCT ps;
GLdouble gldAspect;
GLsizei glnWidth, glnHeight;
switch(msg)
{
case WM_CREATE:
// Select a pixel format and then
// create a rendering context from it.
hRC = SetUpOpenGL(hWnd);
return 0;
case WM_SIZE:
// Redefine the viewing volume and viewport
// when the window size changes.
// Make the RC current since we're going to
// make an OpenGL call here...
hDC = GetDC(hWnd);
wglMakeCurrent(hDC,hRC);
// get the new size of the client window
// note that we size according to the height,
// not the smaller of the height or width.
glnWidth = (GLsizei) LOWORD (lParam);
glnHeight = (GLsizei) HIWORD (lParam);
gldAspect =
(GLdouble)glnWidth/(GLdouble)glnHeight;
// set up a projection matrix to fill the
// client window
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
// a perspective-view matrix...
gluPerspective(
30.0, // Field-of-view angle
gldAspect, // Aspect ratio of view volume
1.0, // Distance to near clipping plane
10.0 ); // Distance to far clipping plane
glViewport( 0, 0, glnWidth, glnHeight );
wglMakeCurrent( NULL, NULL );
ReleaseDC( hWnd, hDC );
return 0;
case WM_PAINT:
// Draw the scene.
// Get a DC, then make the RC current and
// associate with this DC
hDC = BeginPaint( hWnd, &ps );
wglMakeCurrent( hDC, hRC );
DrawOpenGLScene();
// we're done with the RC, so
// deselect it
// (note: This technique is not recommended!)
wglMakeCurrent( NULL, NULL );
EndPaint( hWnd, &ps );
return 0;
case WM_DESTROY:
// Clean up and terminate.
wglDeleteContext( hRC );
PostQuitMessage( 0 );
return 0;
}
// This function handles any messages that we didn't.
// (Which is most messages) It belongs to the OS.
return DefWindowProc( hWnd, msg, wParam, lParam );
}
OpenGL 初始化代码位于 SetUpOpenGL() 中。
HGLRC SetUpOpenGL( HWND hWnd )
{
static PIXELFORMATDESCRIPTOR pfd = {
sizeof (PIXELFORMATDESCRIPTOR), // strcut size
1, // Version number
PFD_DRAW_TO_WINDOW | // Flags, draw to a window,
PFD_SUPPORT_OPENGL, // use OpenGL
PFD_TYPE_RGBA, // RGBA pixel values
24, // 24-bit color
0, 0, 0, // RGB bits & shift sizes.
0, 0, 0, // Don't care about them
0, 0, // No alpha buffer info
0, 0, 0, 0, 0, // No accumulation buffer
32, // 32-bit depth buffer
0, // No stencil buffer
0, // No auxiliary buffers
PFD_MAIN_PLANE, // Layer type
0, // Reserved (must be 0)
0, // No layer mask
0, // No visible mask
0 // No damage mask
};
int nMyPixelFormatID;
HDC hDC;
HGLRC hRC;
hDC = GetDC( hWnd );
nMyPixelFormatID = ChoosePixelFormat( hDC, &pfd );
// catch errors here.
// If nMyPixelFormat is zero, then there's
// something wrong... most likely the window's
// style bits are incorrect (in CreateWindow() )
// or OpenGl isn't installed on this machine
SetPixelFormat( hDC, nMyPixelFormatID, &pfd );
hRC = wglCreateContext( hDC );
ReleaseDC( hWnd, hDC );
return hRC;
}
绘制代码由 DrawOpenGLScene() 函数表示。
void DrawOpenGLScene( )
{
//glEnable( GL_DEPTH_TEST );
//
// Define the modelview transformation.
//
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
// move the viewpoint out to where we can see everything
glTranslatef( 0.0f, 0.0f, -5.0f );
glBegin(GL_TRIANGLES);
glColor3f(1.0,0.0,0.0);//red color for the triangle
glVertex3f(0.0,0.0,0);
glVertex3f(0.0,1.0,0);
glVertex3f(1.0,0.0,0);
glColor3f(0.0,1.0,0.0);//Green color for the triangle
glVertex3f(0.0,0.0,0);
glVertex3f(0.0,1.0,0);
glVertex3f(-1.0,0.0,0);
glColor3f(0.0,0.0,1.0);//Blue color for the triangle
glVertex3f(1.0,0.0,0);
glVertex3f(0.0,-1.0,0);
glVertex3f(-1.0,0.0,0);
glEnd();
glFlush();
}
就是这样
这就是开始使用 OpenGL 的全部内容。
参考文献
- OpenGL 编程指南 - 红皮书。
- OpenGL 参考手册 - 蓝皮书。