OpenGl学习笔记 - 开卷有益

开篇有益

先提供了测试用的"开发包",用Visual Studio 2008打开,点此下载,,,

 

最近又开始学习OpenGl了,不知道能坚持多久,希望能坚持下去吧,

OpenGL是"输出"型的API,就是说,如具体的windows消息接受,窗口创建,消息循环,键盘输入,鼠标输入等功能,在OpenGl看来,它无能为力;

它只是输出内容,就这么简单,它只负责跟自己有关的内容;这保证了它的可移植性等特点,更详细的信息还是自己多在网上搜索下吧,这不是重点.

 

基础中的基础 - windows SDK开发模式简单介绍

windows SDK的"开发模式",执行顺序大概如下:

1,定义WinMain方法,这是入口函数,在WinMain函数中:

 

1. 定义窗口类
2. 注册窗口类
3. 创建窗口类实例
4. 运行该实例
5. 更新该实例

 

2,定义窗口回调函数

 

1. 在回调函数中接受窗口消息
2. 分别为不同的消息做不同的处理,如在创建消息中进行OpenGl的初始化,在退出消息中释放OpenGl的资源

 

大体上就是这个样子,在WinMain函数中的五步是"一气呵成"顺序编写就成,在窗口回调函数中进行实际的渲染工作,

到这里为止,OpenGl可以粉墨登场了,在参考代码中game->RenderWindow(); 这一行是OpenGl调用的"入口函数",

Game类是我们自定义的一个类,它负责OpenGl的初始化工作,好了,在此之前都是windows SDK的内容,

内容不多,但非常重要;

 

参考代码

#include <windows.h>    // Windows的头文件

#include <mmsystem.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <assert.h>
#include <gl\gl.h>        // OpenGL32库的头文件
#include <gl\glu.h>        // GLu32库的头文件
//#include <gl\glaux.h>    // GLaux库的头文件

#pragma comment( lib, "winmm.lib")
#pragma comment( lib, "opengl32.lib")    // OpenGL32连接库
#pragma comment( lib, "glu32.lib")        // GLu32连接库
//#pragma comment( lib, "glaux.lib")        // GLaux连接库
#define KEY_DOWN(vk_code)((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0);

 

#include <windows.h> 
#include "inc.h"
#include "game.h"

HDC        hDc;                // GDI设备句柄,将窗口连接到 GDI( 图形设备接口)
HGLRC    hRC=NULL;            // 渲染描述句柄,将OpenGL调用连接到设备描述表 
HWND    hWnd=NULL;            // 保存 Windows 分配给程序的窗口句柄
INT        gWidth = 200;
INT        gHeight = 200;
Game *game = new Game();

//声明回调函数
LRESULT CALLBACK WindowProcedure(HWND hwnd , UINT message, WPARAM wParam, LPARAM lParam);

/* Make the class name into a global variable */ 
char szClassName[ ] = "kkun"; 

int WINAPI WinMain (HINSTANCE hThisInstance,HINSTANCE hPrevInstance, LPSTR lpszArgument, int nFunsterStil) { 
    
    HWND             hwnd;                       /* This is the handle for our window */ 
    MSG              messages;                   /* Here messages to the application are saved */ 
    
    //注册窗口类
    WNDCLASSEX       wc;
    wc.hInstance =           hThisInstance; 
    wc.lpszClassName =       szClassName; 
    wc.lpfnWndProc =         WindowProcedure;    /* This function is called by windows */ 
    wc.style =               CS_DBLCLKS;         /* Catch double-clicks */ 
    wc.cbSize = sizeof (WNDCLASSEX); 
    wc.hIcon = LoadIcon (NULL, IDI_APPLICATION); 
    wc.hIconSm = LoadIcon (NULL, IDI_APPLICATION); 
    wc.hCursor = LoadCursor (NULL, IDC_ARROW); 
    wc.lpszMenuName = NULL;                          /* No menu */ 
    wc.cbClsExtra = 0;                               /* No extra bytes after the window class */ 
    wc.cbWndExtra = 0;                               /* structure or the window instance */ 
    wc.hbrBackground = (HBRUSH) COLOR_BACKGROUND; 

    if (!RegisterClassEx (&wc)) 
    return 0; 


    //创建窗口
    hwnd = CreateWindowEx ( 
                        0,                      /* Extended possibilites for variation */ 
                        szClassName,            /* Classname */ 
                        "OpenGl",          /* Title Text */ 
                        WS_OVERLAPPEDWINDOW,    /* default window */ 
                        CW_USEDEFAULT,          /* Windows decides the position */ 
                        CW_USEDEFAULT,          /* where the window ends up on the screen */ 
                        gWidth,                    /* The programs width */ 
                        gHeight,                    /* and height in pixels */ 
                        HWND_DESKTOP,           /* The window is a child-window to desktop */ 
                        NULL,                   /* No menu */ 
                        hThisInstance,          /* Program Instance handler */ 
                        NULL                    /* No Window Creation data */ ); 

                        /* Make the window visible on the screen */ 
    ShowWindow (hwnd, nFunsterStil); 
    UpdateWindow(hwnd);

    //消息循环
    MSG msg; 
    BOOL fMessage;
    PeekMessage(&msg, NULL, 0U, 0U, PM_NOREMOVE);
    while(msg.message != WM_QUIT){   
        fMessage = PeekMessage(&msg, NULL, 0U, 0U, PM_REMOVE);
        if(fMessage){ 
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }else{
            //渲染窗口
            game->RenderWindow();
        }
    }

    return msg.wParam;
}


//消息回调函数
LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) { 
    switch (message) /* handle the messages */ 
    { 
        case WM_CREATE:
            hDc = GetDC(hwnd);
            game->SetupFixelFormat(hDc);
            break;
        case WM_CLOSE:
            game->Remove();
            PostQuitMessage (0);
            break;
        case WM_SIZE:
            game->InitWindow(gWidth,gHeight);
            break;
        case WM_KEYUP:
            switch(wParam){
                case VK_ESCAPE:
                    game->Remove();
                    PostQuitMessage(0);
                    break;
            }
            break;
        case WM_DESTROY: 
            PostQuitMessage (0); /* send a WM_QUIT to the message queue */ 
            break; 
        default: /* for messages that we don't deal with */ 
        return DefWindowProc (hwnd, message, wParam, lParam); 
    }
    return 0; 
}