实例：FreakOut
在沉溺于所讨论的有关Windows、DirectX 和3D 图形之前，应当暂停一下，先给你看一个完整的游戏——虽然简单了一点，但毫无疑问是一个完整的游戏。你会看到一个实际的游戏循环和一些图形功能调用，最后一霎那就可以通过编译。不错吧？跟我来吧！
问题是我们现在才讲到第一章。我不应该使用后面章节中的内容……这有点像作弊，对吧？因此，我决定要做的是让你习惯于使用黑黑（black box）API来进行游戏编程。基于这个要求，我要提一个问题“要制作一个类似Breakout（打砖块）的2D游戏，其最低要求是什么？”我们真正所需要的是下面的功能：
? 在任意图像模式中切换
? 在屏幕上画各种颜色的矩形
? 获取键盘输入
? 使用一些定时函数同步游戏循环
? 在屏幕上画彩色文字串
因此我建了一个名为BLACKBOX.CPP|H的库。它封装了一套DirectX函数集（限于DirectDraw），并且包含实现所需功能的支持代码。妙处是，读者根本不需要看这些代码，只需依照函数原型来使用这些函数就可以了，并与BLACKBOX.CPP|H连接来产生.EXE可执行文件。
以BLACKBOX库为基础，我编写了一个名字为FreakOut的游戏，这个游戏演示了本章中所讨论的许多概念。FreakOut 游戏包含真正游戏的全部主要组成部分，包括：游戏循环、计分、关卡，甚至还有为球而写的迷你物理模型。真是可爱。图1.9 是一幅游戏运行中的屏幕画面。显然它比不上Arkanoid（经典的打砖块类游戏），但4 个小时的工作有此成果也不赖！
图1.9 FreakOut游戏的截屏
在阅读游戏源代码之前，我希望读者能看一下工程和游戏各组成部分是如何协调一致的。参见图1.10。
图1.10 FreakOut 的结构
从图中可以看到，游戏由下面文件构成：
FREAKOUT.CPP——游戏的主要逻辑，使用BLACKBOX.CPP，创建一个最小化的Win32应用程序。
BLACKBOX.CPP——游戏库（请不要偷看：）。
BLACKBOX.H——游戏库的头文件。
DDRAW.LIB——用于生成应用程序的DirectDraw输入库。其中并不含有真正的DirectX代码。它主要是用作让用户调用的中间库，然后轮流调用进行实际工作的DDRAW.DLL动态链接库。它可以在DirectX SDK 安装目录下的LIB子目录内被找到。
DDRAW.DLL——运行时（Runtime）的DirectDraw 库，实际上含有通过DDRAW.LIB 输入库调用DirectDraw 接口函数的COM 执行程序。不必为此担心；只要确认已经安装了DirectX运行时文件即可。
为了通过编译，需要将BLACKBOX.CPP和FREAKOUT.CPP加入工程里面，连接上DDRAW.LIB库文件，并确保BLACKBOX.H在头文件搜索路径或工作目录里，以便编译器可以正确地找到它。
现在我们已大致了解了FreakOut的结构。让我们看一下BLACKOUT.H头文件，看看它包含了哪些函数。
程序清单1.2 BLACKOUT.H 头文件
// BLACKBOX.H - Header file for demo game engine library
// watch for multiple inclusions
#ifndef BLACKBOX
#define BLACKBOX
// DEFINES
// default screen size
#define SCREEN_WIDTH 640 // size of screen
#define SCREEN_HEIGHT 480
#define SCREEN_BPP 8 // bits per pixel
#define MAX_COLORS 256 // maximum colors
// MACROS /
// these read the keyboard asynchronously
#define KEY_DOWN(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0)
#define KEY_UP(vk_code) ((GetAsyncKeyState(vk_code) & 0x8000) ? 0 : 1)
// initializes a direct draw struct
#define DD_INIT_STRUCT(ddstruct) {memset(&ddstruct,0,sizeof(ddstruct));
ddstruct.dwSize=sizeof(ddstruct); }
// TYPES //
// basic unsigned types
typedef unsigned short USHORT;
typedef unsigned short WORD;
typedef unsigned char UCHAR;
typedef unsigned char BYTE;
// EXTERNALS //
extern LPDIRECTDRAW7 lpdd; // dd object
extern LPDIRECTDRAWSURFACE7 lpddsprimary; // dd primary surface
extern LPDIRECTDRAWSURFACE7 lpddsback; // dd back surface
extern LPDIRECTDRAWPALETTE lpddpal; // a pointer dd palette
extern LPDIRECTDRAWCLIPPER lpddclipper; // dd clipper
extern PALETTEENTRY palette[256]; // color palette
extern PALETTEENTRY save_palette[256]; // used to save palettes
extern DDSURFACEDESC2 ddsd; // a ddraw surface description struct
extern DDBLTFX ddbltfx; // used to fill
extern DDSCAPS2 ddscaps; // a ddraw surface capabilities struct
extern HRESULT ddrval; // result back from dd calls
extern DWORD start_clock_count; // used for timing
// these defined the general clipping rectangle
extern int min_clip_x, // clipping rectangle
max_clip_x,
min_clip_y,
max_clip_y;
// these are overwritten globally by DD_Init()
extern int screen_width, // width of screen
screen_height, // height of screen
screen_bpp; // bits per pixel
// PROTOTYPES /
// DirectDraw functions
int DD_Init(int width, int height, int bpp);
int DD_Shutdown(void);
LPDIRECTDRAWCLIPPER DD_Attach_Clipper(LPDIRECTDRAWSURFACE7 lpdds,
int num_rects, LPRECT clip_list);
int DD_Flip(void);
int DD_Fill_Surface(LPDIRECTDRAWSURFACE7 lpdds,int color);
// general utility functions
DWORD Start_Clock(void);
DWORD Get_Clock(void);
DWORD Wait_Clock(DWORD count);
// graphics functions
int Draw_Rectangle(int x1, int y1, int x2, int y2,
int color,LPDIRECTDRAWSURFACE7 lpdds=lpddsback);
// gdi functions
int Draw_Text_GDI(char *text, int x,int y,COLORREF color,
LPDIRECTDRAWSURFACE7 lpdds=lpddsback);
int Draw_Text_GDI(char *text, int x,int y,int color,
LPDIRECTDRAWSURFACE7 lpdds=lpddsback);
#endif
现在，不要花费太多时间绞尽脑汁研究这里的程序代码，搞清楚那些神秘的全局变量究竟表示什么并不重要。让我们来看一看这些函数。如你所想，这里有实现我们的简单图形界面所需的全部函数。基于这个图形界面和最小化的Win32 应用程序（我们要做的Windows 编程工作越少越好）的基础上，我创建了游戏FREAKOUT.CPP，如清单1.3 所示。请认真地看一看，尤其是游戏主循环和对游戏处理功能的调用。
程序清单1.3 FREAKOUT.CPP 源文件
// INCLUDES ///
#define WIN32_LEAN_AND_MEAN // include all macros
#define INITGUID // include all GUIDs
#include // include important windows stuff
#include
#include
#include // include important C/C++ stuff
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include // directX includes
#include "blackbox.h" // game library includes
// DEFINES
// defines for windows
#define WINDOW_CLASS_NAME "WIN3DCLASS" // class name
#define WINDOW_WIDTH 640 // size of window
#define WINDOW_HEIGHT 480
// states for game loop
#define GAME_STATE_INIT 0
#define GAME_STATE_START_LEVEL 1
#define GAME_STATE_RUN 2
#define GAME_STATE_SHUTDOWN 3
#define GAME_STATE_EXIT 4
// block defines
#define NUM_BLOCK_ROWS 6
#define NUM_BLOCK_COLUMNS 8
#define BLOCK_WIDTH 64
#define BLOCK_HEIGHT 16
#define BLOCK_ORIGIN_X 8
#define BLOCK_ORIGIN_Y 8
#define BLOCK_X_GAP 80
#define BLOCK_Y_GAP 32
// paddle defines
#define PADDLE_START_X (SCREEN_WIDTH/2 - 16)
#define PADDLE_START_Y (SCREEN_HEIGHT - 32);
#define PADDLE_WIDTH 32
#define PADDLE_HEIGHT 8
#define PADDLE_COLOR 191
// ball defines
#define BALL_START_Y (SCREEN_HEIGHT/2)
#define BALL_SIZE 4
// PROTOTYPES /
// game console
int Game_Init(void *parms=NULL);
int Game_Shutdown(void *parms=NULL);
int Game_Main(void *parms=NULL);
// GLOBALS
HWND main_window_handle = NULL; // save the window handle
HINSTANCE main_instance = NULL; // save the instance
int game_state = GAME_STATE_INIT; // starting state
int paddle_x = 0, paddle_y = 0; // tracks position of paddle
int ball_x = 0, ball_y = 0; // tracks position of ball
int ball_dx = 0, ball_dy = 0; // velocity of ball
int score = 0; // the score
int level = 1; // the current level
int blocks_hit = 0; // tracks number of blocks hit
// this contains the game grid data
UCHAR blocks[NUM_BLOCK_ROWS][NUM_BLOCK_COLUMNS];
// FUNCTIONS //
LRESULT CALLBACK WindowProc(HWND hwnd,
UINT msg,
WPARAM wparam,
LPARAM lparam)
{
// this is the main message handler of the system
PAINTSTRUCT ps; // used in WM_PAINT
HDC hdc; // handle to a device context
// what is the message
switch(msg)
{
case WM_CREATE:
{
// do initialization stuff here
return(0);
} break;
case WM_PAINT:
{
// start painting
hdc = BeginPaint(hwnd,&ps);
// the window is now validated
// end painting
EndPaint(hwnd,&ps);
return(0);
} break;
case WM_DESTROY:
{
// kill the application
PostQuitMessage(0);
return(0);
} break;
default:break;
} // end switch
// process any messages that we didn't take care of
return (DefWindowProc(hwnd, msg, wparam, lparam));
} // end WinProc
// WINMAIN
int WINAPI WinMain(HINSTANCE hinstance,
HINSTANCE hprevinstance,
LPSTR lpcmdline,
int ncmdshow)
{
// this is the winmain function
WNDCLASS winclass; // this will hold the class we create
HWND hwnd; // generic window handle
MSG msg; // generic message
HDC hdc; // generic dc
PAINTSTRUCT ps; // generic paintstruct
// first fill in the window class structure
winclass.style = CS_DBLCLKS | CS_OWNDC |
CS_HREDRAW | CS_VREDRAW;
winclass.lpfnWndProc = WindowProc;
winclass.cbClsExtra = 0;
winclass.cbWndExtra = 0;
winclass.hInstance = hinstance;
winclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
winclass.hCursor = LoadCursor(NULL, IDC_ARROW);
winclass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
winclass.lpszMenuName = NULL;
winclass.lpszClassName = WINDOW_CLASS_NAME;
// register the window class
if (!RegisterClass(&winclass))
return(0);
// create the window, note the use of WS_POPUP
if (!(hwnd = CreateWindow(WINDOW_CLASS_NAME, // class
"WIN3D Game Console", // title
WS_POPUP | WS_VISIBLE,
0,0, // initial x,y
GetSystemMetrics(SM_CXSCREEN), // initial width
GetSystemMetrics(SM_CYSCREEN), // initial height
NULL, // handle to parent
NULL, // handle to menu
hinstance, // instance
NULL))) // creation parms
return(0);
// hide mouse
ShowCursor(FALSE);
// save the window handle and instance in a global
main_window_handle = hwnd;
main_instance = hinstance;
// perform all game console specific initialization
Game_Init();
// enter main event loop
while(1)
{
if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))
{
// test if this is a quit
if (msg.message == WM_QUIT)
break;
// translate any accelerator keys
TranslateMessage(&msg);
// send the message to the window proc
DispatchMessage(&msg);
} // end if
// main game processing goes here
Game_Main();
} // end while
// shutdown game and release all resources
Game_Shutdown();
// show mouse
ShowCursor(TRUE);
// return to Windows like this
return(msg.wParam);
} // end WinMain
// T3DX GAME PROGRAMMING CONSOLE FUNCTIONS
int Game_Init(void *parms)
{
// this function is where you do all the initialization
// for your game
// return success
return(1);
} // end Game_Init
///
int Game_Shutdown(void *parms)
{
// this function is where you shutdown your game and
// release all resources that you allocated
// return success
return(1);
} // end Game_Shutdown
///
void Init_Blocks(void)
{
// initialize the block field
for (int row=0; row < NUM_BLOCK_ROWS; row++)
for (int col=0; col < NUM_BLOCK_COLUMNS; col++)
blocks[row][col] = row*16+col*3+16;
} // end Init_Blocks
///
void Draw_Blocks(void)
{
// this function draws all the blocks in row major form
int x1 = BLOCK_ORIGIN_X, // used to track current position
y1 = BLOCK_ORIGIN_Y;
// draw all the blocks
for (int row=0; row < NUM_BLOCK_ROWS; row++)
{
// reset column position
x1 = BLOCK_ORIGIN_X;
// draw this row of blocks
for (int col=0; col < NUM_BLOCK_COLUMNS; col++)
{
// draw next block (if there is one)
if (blocks[row][col]!=0)
{
// draw block
Draw_Rectangle(x1-4,y1+4,
x1+BLOCK_WIDTH-4,y1+BLOCK_HEIGHT+4,0);
Draw_Rectangle(x1,y1,x1+BLOCK_WIDTH,
y1+BLOCK_HEIGHT,blocks[row][col]);
} // end if
// advance column position
x1+=BLOCK_X_GAP;
} // end for col
// advance to next row position
y1+=BLOCK_Y_GAP;
} // end for row
} // end Draw_Blocks
///
void Process_Ball(void)
{
// this function tests if the ball has hit a block or the paddle
// if so, the ball is bounced and the block is removed from
// the playfield note: very cheesy collision algorithm :)
// first test for ball block collisions
// the algorithm basically tests the ball against each
// block's bounding box this is inefficient, but easy to
// implement, later we'll see a better way
int x1 = BLOCK_ORIGIN_X, // current rendering position
y1 = BLOCK_ORIGIN_Y;
int ball_cx = ball_x+(BALL_SIZE/2), // computer center of ball
ball_cy = ball_y+(BALL_SIZE/2);
// test of the ball has hit the paddle
if (ball_y > (SCREEN_HEIGHT/2) && ball_dy > 0)
{
// extract leading edge of ball
int x = ball_x+(BALL_SIZE/2);
int y = ball_y+(BALL_SIZE/2);
// test for collision with paddle
if ((x >= paddle_x && x <= paddle_x+PADDLE_WIDTH) &&
(y >= paddle_y && y <= paddle_y+PADDLE_HEIGHT))
{
// reflect ball
ball_dy=-ball_dy;
// push ball out of paddle since it made contact
ball_y+=ball_dy;
// add a little english to ball based on motion of paddle
if (KEY_DOWN(VK_RIGHT))
ball_dx-=(rand()%3);
else
if (KEY_DOWN(VK_LEFT))
ball_dx+=(rand()%3);
else
ball_dx+=(-1+rand()%3);
// test if there are no blocks, if so send a message
// to game loop to start another level
if (blocks_hit >= (NUM_BLOCK_ROWS*NUM_BLOCK_COLUMNS))
{
game_state = GAME_STATE_START_LEVEL;
level++;
} // end if
// make a little noise
MessageBeep(MB_OK);
// return
return;
} // end if
} // end if
// now scan thru all the blocks and see if ball hit blocks
for (int row=0; row < NUM_BLOCK_ROWS; row++)
{
// reset column position
x1 = BLOCK_ORIGIN_X;
// scan this row of blocks
for (int col=0; col < NUM_BLOCK_COLUMNS; col++)
{
// if there is a block here then test it against ball
if (blocks[row][col]!=0)
{
// test ball against bounding box of block
if ((ball_cx > x1) && (ball_cx < x1+BLOCK_WIDTH) &&
(ball_cy > y1) && (ball_cy < y1+BLOCK_HEIGHT))
{
// remove the block
blocks[row][col] = 0;
// increment global block counter, so we know
// when to start another level up
blocks_hit++;
// bounce the ball
ball_dy=-ball_dy;
// add a little english
ball_dx+=(-1+rand()%3);
// make a little noise
MessageBeep(MB_OK);
// add some points
score+=5*(level+(abs(ball_dx)));
// that's it -- no more block
return;
} // end if
} // end if
// advance column position
x1+=BLOCK_X_GAP;
} // end for col
// advance to next row position
y1+=BLOCK_Y_GAP;
} // end for row
} // end Process_Ball
///
int Game_Main(void *parms)
{
// this is the workhorse of your game it will be called
// continuously in real-time this is like main() in C
// all the calls for your game go here!
char buffer[80]; // used to print text
// what state is the game in?
if (game_state == GAME_STATE_INIT)
{
// initialize everything here graphics
DD_Init(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP);
// seed the random number generator
// so game is different each play
srand(Start_Clock());
// set the paddle position here to the middle bottom
paddle_x = PADDLE_START_X;
paddle_y = PADDLE_START_Y;
// set ball position and velocity
ball_x = 8+rand()%(SCREEN_WIDTH-16);
ball_y = BALL_START_Y;
ball_dx = -4 + rand()%(8+1);
ball_dy = 6 + rand()%2;
// transition to start level state
game_state = GAME_STATE_START_LEVEL;
} // end if
else
if (game_state == GAME_STATE_START_LEVEL)
{
// get a new level ready to run
// initialize the blocks
Init_Blocks();
// reset block counter
blocks_hit = 0;
// transition to run state
game_state = GAME_STATE_RUN;
} // end if
///
else
if (game_state == GAME_STATE_RUN)
{
// start the timing clock
Start_Clock();
// clear drawing surface for the next frame of animation
Draw_Rectangle(0,0,SCREEN_WIDTH-1, SCREEN_HEIGHT-1,200);
// move the paddle
if (KEY_DOWN(VK_RIGHT))
{
// move paddle to right
paddle_x+=8;
// make sure paddle doesn't go off screen
if (paddle_x > (SCREEN_WIDTH-PADDLE_WIDTH))
paddle_x = SCREEN_WIDTH-PADDLE_WIDTH;
} // end if
else
if (KEY_DOWN(VK_LEFT))
{
// move paddle to right
paddle_x-=8;
// make sure paddle doesn't go off screen
if (paddle_x < 0)
paddle_x = 0;
} // end if
// draw blocks
Draw_Blocks();
// move the ball
ball_x+=ball_dx;
ball_y+=ball_dy;
// keep ball on screen, if the ball hits the edge of
// screen then bounce it by reflecting its velocity
if (ball_x > (SCREEN_WIDTH - BALL_SIZE) || ball_x < 0)
{
// reflect x-axis velocity
ball_dx=-ball_dx;
// update position
ball_x+=ball_dx;
} // end if
// now y-axis
if (ball_y < 0)
{
// reflect y-axis velocity
ball_dy=-ball_dy;
// update position
ball_y+=ball_dy;
} // end if
else
// penalize player for missing the ball
if (ball_y > (SCREEN_HEIGHT - BALL_SIZE))
{
// reflect y-axis velocity
ball_dy=-ball_dy;
// update position
ball_y+=ball_dy;
// minus the score
score-=100;
} // end if
// next watch out for ball velocity getting out of hand
if (ball_dx > 8) ball_dx = 8;
else
if (ball_dx < -8) ball_dx = -8;
// test if ball hit any blocks or the paddle
Process_Ball();
// draw the paddle and shadow
Draw_Rectangle(paddle_x-8, paddle_y+8,
paddle_x+PADDLE_WIDTH-8,
paddle_y+PADDLE_HEIGHT+8,0);
Draw_Rectangle(paddle_x, paddle_y,
paddle_x+PADDLE_WIDTH,
paddle_y+PADDLE_HEIGHT,PADDLE_COLOR);
// draw the ball
Draw_Rectangle(ball_x-4, ball_y+4, ball_x+BALL_SIZE-4,
ball_y+BALL_SIZE+4, 0);
Draw_Rectangle(ball_x, ball_y, ball_x+BALL_SIZE,
ball_y+BALL_SIZE, 255);
// draw the info
sprintf(buffer,"F R E A K O U T Score %d //
Level %d",score,level);
Draw_Text_GDI(buffer, 8,SCREEN_HEIGHT-16, 127);
// flip the surfaces
DD_Flip();
// sync to 33ish fps
Wait_Clock(30);
// check if user is trying to exit
if (KEY_DOWN(VK_ESCAPE))
{
// send message to windows to exit
PostMessage(main_window_handle, WM_DESTROY,0,0);
// set exit state
game_state = GAME_STATE_SHUTDOWN;
} // end if
} // end if
///
else
if (game_state == GAME_STATE_SHUTDOWN)
{
// in this state shut everything down and release resources
DD_Shutdown();
// switch to exit state
game_state = GAME_STATE_EXIT;
} // end if
// return success
return(1);
} // end Game_Main
哈哈，酷吧？这就是一个完整的Win32/DirectX游戏了，至少几乎是完整的了。BLACKOUT.CPP源文件中有好几百行代码，但是我们可以将其视为某人（我！）编写的DirectX的一部分。不管怎样说，还是让我们迅速浏览一下程序清单1.3的内容吧。
首先，Windows 需要一个事件循环。这是所有Windows程序的标准结构，因为Windows几乎完全是事件驱动的。但是游戏却不是事件驱动的，无论用户在干什么，它们都在一直运行。因此，我们至少需要支持小型事件循环以配合Windows。执行这项功能的代码位于WinMain()中。WinMain() 是所有Windows 程序的主要入口点，就好比main()是所有DOS/UNIX 程序中的入口点一样。FreakOut 的WinMain()创建一个窗口并进入事件循环。当Windows需要作某些工作时，就随它去。当所有的基本事件处理都结束时，调用Game_Main()。Game_Main是实际运行游戏程序的部分。
如果愿意的话，你可以不停地在Game_Main()中循环，而不释放回到WinMain()主事件循环体中。但这样做不是件好事，因为Windows会得不到任何信息。哎，我们该做的是让游戏在运行一帧时间的动画和逻辑之后，返回到WinMain()。这样的话，Windows可以继续响应和处理信息。如果所有这些听起来像是幻术的话，请不要担心——在下一章中情况还会更糟。
进入Game_Main()后，FreakOut的游戏逻辑开始被执行。游戏图像被渲染到一个不直接显示出来的工作缓冲区，尔后通过调用DD_FLIP()而在循环结束时在显示屏上显示出来。因此我希望你阅读一下全部的游戏状态，一行一行地过一遍一遍游戏循环的每一部分，了解工作原理。要启动游戏，只须双击FREAKOUT.EXE，游戏程序会立即启动。游戏控制方式如下：
右箭头键——向右移动挡板。
左箭头键——向左移动挡板。
Esc键——退回Windows。
还有，如果你错过一个球的话，将被罚掉100分，可要仔细盯紧啊！
如果你已经明白了游戏代码和玩法，不妨试着修改一下游戏。你可以增加不同的背景颜色（0~255 是有效的颜色）、增加更多的球、可以改变挡板的大小以及加上更多的声音效果（目前我只用到了Win32 API 中的MessageBeep()函数）
总结
这大概是我所写的最快的一章游戏编程入门教程了！我们提及了大量的基础内容，但是还只能算作是本书的缩略版本（就像印在封底的那样）。我只想让读者对本书中我们将学习和讨论的内容有一个感性认识。另外，阅读一个完整的游戏总是有益的，因为这带来许多需要读者思考的问题。
在进入第二章之前，请先确保你能够轻松编译FreakOut游戏。如果还不行的话，请立即翻开编译器的书并且RTFM（阅读那恼人的使用手册！）。我等着你们。
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