c++ - Direct X 9 - 三角形没有出现

Question

目前，在开始编写程序之前，我正在用 DirectX 做一些测试用例。而现在，我已经弄乱了下面的代码一天左右。我在互联网上查看类似问题时修改了代码。但最终，它也没有按照我想要的方式工作。有人能告诉我我到底做错了什么吗？也许其他人可以解决这个问题。

// TetrisClone.cpp : Defines the entry point for the application.
//

#include "stdafx.h"
#include "TetrisClone.h"
#include <d3d9.h>
#include <d3dx9.h>


#define MAX_LOADSTRING 100
#define SCREEN_WIDTH 800
#define SCREEN_HEIGHT 600

#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZ|D3DFVF_DIFFUSE)

//for testing purposes
struct CUSTOMVERTEX
{
    FLOAT x, y, z; //position
    DWORD color; //Color
};

// global declarations for Direct3d
LPDIRECT3D9 d3d;    // the pointer to our Direct3D interface
LPDIRECT3DDEVICE9 d3ddev;    // the pointer to the device class
LPDIRECT3DVERTEXBUFFER9 g_pVB = NULL;

// function prototypes
void initD3D(HWND hWnd);    // sets up and initializes Direct3D
void render_frame(void);    // renders a single frame
void cleanD3D(void);    // closes Direct3D and releases memory
void init_graphics(void);    // 3D declarations

// Global Variables:
HINSTANCE hInst;                                // current instance
TCHAR szTitle[MAX_LOADSTRING];                  // The title bar text
TCHAR szWindowClass[MAX_LOADSTRING];            // the main window class name

// Forward declarations of functions included in this code module:
ATOM                MyRegisterClass(HINSTANCE hInstance);
BOOL                InitInstance(HINSTANCE, int);
LRESULT CALLBACK    WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK    About(HWND, UINT, WPARAM, LPARAM);

int APIENTRY _tWinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPTSTR    lpCmdLine,
                     int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    // TODO: Place code here.
    MSG msg;
    HACCEL hAccelTable;

    // Initialize global strings
    LoadString(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
    LoadString(hInstance, IDC_TETRISCLONE, szWindowClass, MAX_LOADSTRING);
    MyRegisterClass(hInstance);

    // Perform application initialization:
    if (!InitInstance (hInstance, nCmdShow))
    {
        return FALSE;
    }

    hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_TETRISCLONE));

    // Main message loop:
    while(TRUE)
    {
        // Check to see if any messages are waiting in the queue
        while(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
        {
            // Translate the message and dispatch it to WindowProc()
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }

        // If the message is WM_QUIT, exit the while loop
        if(msg.message == WM_QUIT)
            break;

        render_frame();
    }

    cleanD3D();
    return (int) msg.wParam;
}



//
//  FUNCTION: MyRegisterClass()
//
//  PURPOSE: Registers the window class.
//
//  COMMENTS:
//
//    This function and its usage are only necessary if you want this code
//    to be compatible with Win32 systems prior to the 'RegisterClassEx'
//    function that was added to Windows 95. It is important to call this function
//    so that the application will get 'well formed' small icons associated
//    with it.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
    WNDCLASSEX wcex;

    wcex.cbSize = sizeof(WNDCLASSEX);

    wcex.style          = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc    = WndProc;
    wcex.cbClsExtra     = 0;
    wcex.cbWndExtra     = 0;
    wcex.hInstance      = hInstance;
    wcex.hIcon          = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_TETRISCLONE));
    wcex.hCursor        = LoadCursor(NULL, IDC_ARROW);
    wcex.hbrBackground  = (HBRUSH)(COLOR_GRAYTEXT);
    wcex.lpszMenuName   = MAKEINTRESOURCE(IDC_TETRISCLONE);
    wcex.lpszClassName  = szWindowClass;
    wcex.hIconSm        = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));

    return RegisterClassEx(&wcex);
}

//
//   FUNCTION: InitInstance(HINSTANCE, int)
//
//   PURPOSE: Saves instance handle and creates main window
//
//   COMMENTS:
//
//        In this function, we save the instance handle in a global variable and
//        create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
   HWND hWnd;

   hInst = hInstance; // Store instance handle in our global variable

   hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, CW_USEDEFAULT, SCREEN_WIDTH, SCREEN_HEIGHT, NULL, NULL, hInstance, NULL);

   if (!hWnd)
   {
      return FALSE;
   }

   ShowWindow(hWnd, nCmdShow);

   // set up and initialize Direct3D
   initD3D(hWnd);

   UpdateWindow(hWnd);

   return TRUE;
}

//
//  FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
//  PURPOSE:  Processes messages for the main window.
//
//  WM_COMMAND  - process the application menu
//  WM_PAINT    - Paint the main window
//  WM_DESTROY  - post a quit message and return
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    int wmId, wmEvent;
    PAINTSTRUCT ps;
    HDC hdc;

    switch (message)
    {
    case WM_COMMAND:
        wmId    = LOWORD(wParam);
        wmEvent = HIWORD(wParam);
        // Parse the menu selections:
        switch (wmId)
        {
        case IDM_ABOUT:
            DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
            break;
        case IDM_EXIT:
            DestroyWindow(hWnd);
            break;
        default:
            return DefWindowProc(hWnd, message, wParam, lParam);
        }
        break;
    case WM_PAINT:
        hdc = BeginPaint(hWnd, &ps);
        // TODO: Add any drawing code here...
        EndPaint(hWnd, &ps);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

// Message handler for about box.
INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
    UNREFERENCED_PARAMETER(lParam);
    switch (message)
    {
    case WM_INITDIALOG:
        return (INT_PTR)TRUE;

    case WM_COMMAND:
        if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
        {
            EndDialog(hDlg, LOWORD(wParam));
            return (INT_PTR)TRUE;
        }
        break;
    }
    return (INT_PTR)FALSE;
}

/***
    Direct3d functions

***/

// this function initializes and prepares Direct3D for use
void initD3D(HWND hWnd)
{
    d3d = Direct3DCreate9(D3D_SDK_VERSION);    // create the Direct3D interface

    D3DPRESENT_PARAMETERS d3dpp;    // create a struct to hold various device information

    ZeroMemory(&d3dpp, sizeof(d3dpp));    // clear out the struct for use
    d3dpp.Windowed = TRUE;    // program windowed, not fullscreen
    d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;    // discard old frames
    d3dpp.hDeviceWindow = hWnd;    // set the window to be used by Direct3D

    // create a device class using this information and information from the d3dpp stuct
    d3d->CreateDevice(D3DADAPTER_DEFAULT,
                      D3DDEVTYPE_HAL,
                      hWnd,
                      D3DCREATE_SOFTWARE_VERTEXPROCESSING,
                      &d3dpp,
                      &d3ddev);

    init_graphics();
}

// this is the function used to render a single frame
void render_frame(void)
{

    // clear the window to a deep blue
    d3ddev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 40, 100), 1.0f, 0);

    d3ddev->BeginScene();    // begins the 3D scene

        //set FVF
    d3ddev->SetFVF(D3DFVF_CUSTOMVERTEX);

    //setting stream source
    d3ddev->SetStreamSource(0, g_pVB, 0, sizeof(CUSTOMVERTEX));

    // do 3D rendering on the back buffer here

    //drawing triangle
    d3ddev->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 1);

    d3ddev->EndScene();    // ends the 3D scene

    d3ddev->Present(NULL, NULL, NULL, NULL);    // displays the created frame
}

// this is the function that puts the 3D models into video RAM
void init_graphics(void)
{
    // create the vertices using the CUSTOMVERTEX struct
    CUSTOMVERTEX vertices[] =
    {
        { 400.0f, 62.5f, 0.0f, D3DCOLOR_XRGB(0, 0, 255), },
        { 650.0f, 500.0f, 0.0f, D3DCOLOR_XRGB(0, 255, 0), },
        { 150.0f, 500.0f, 0.0f, D3DCOLOR_XRGB(255, 0, 0), },
    };

    // create a vertex buffer interface called v_buffer
    d3ddev->CreateVertexBuffer(3*sizeof(CUSTOMVERTEX),
                               0,
                               D3DFVF_CUSTOMVERTEX,
                               D3DPOOL_MANAGED,
                               &g_pVB,
                               NULL);

    VOID* pVoid;    // a void pointer

    // lock v_buffer and load the vertices into it
    g_pVB->Lock(0, 0, (void**)&pVoid, 0);
    memcpy(pVoid, vertices, sizeof(vertices));
    g_pVB->Unlock();
}

// this is the function that cleans up Direct3D and COM
void cleanD3D(void)
{
    g_pVB->Release();
    d3ddev->Release();    // close and release the 3D device
    d3d->Release();    // close and release Direct3D
}

Answer 1

由于您没有设置相机并且没有对您的顶点进行任何变换，因此，您应该将您的顶点设置在长方体的范围内(透视投影变换后)，即

-1 << 1 << 1
-1 << y << 1
 0 << z << 1

以下更改将使您的三角形可见。

  CUSTOMVERTEX vertices[] =
    {
        { 0.0f, 0.0, 0.0f, D3DCOLOR_XRGB(0, 0, 255), },
        { 0.0f, 1.0f, 0.0f, D3DCOLOR_XRGB(0, 255, 0), },
        { 1.0f, 0.0f, 0.0f, D3DCOLOR_XRGB(255, 0, 0), },
    };

有很多原因会导致 Direct3D 程序中的几何体/模型不可见，我在下面列出了一些。

禁用/启用照明

通常，我们需要在渲染过程中启用照明，但是如果您使用 LT(Lit and Transformed) 顶点格式，这意味着您定义了顶点的颜色并为其使用屏幕坐标，这告诉 Direct3D 引擎:“嘿，做不光照和变换我的顶点，我会做的!”，在你的代码中你没有使用 LT 格式，这意味着你应该变换和光照你的顶点，但你没有任何光照设置，所以你会得到一个黑色三角形，事实上，你什么也没得到，因为顶点坐标不在视野范围内。

顶点坐标

我们通常在物体空间指定顶点坐标，然后将它们变换到世界空间-> View 空间->投影空间->屏幕空间，在你上面的代码中，你没有做任何传递，但是你的顶点坐标太大了，透视变换后超出长方体范围，范围为-1 << x << 1, -1 << y << 1, 0 << z << 1。

背面剔除模式

这也是一个非常重要的考虑因素，默认情况下，Direct3D 使用将剔除所有逆时针定义的面，请参阅此线程 Odd behaviour when trying to create triangle using TriangleStrip Topologu详情。

相机设置

首先，确保您的相机面向您正在绘制的内容，然后设置正确的距离。您为顶点使用大坐标，因此，您应该将相机设置为远离您正在渲染的几何体，否则您将什么也看不到。

你什么都没画

这个项目看起来有点搞笑，但确实发生了，当我们要测试渲染是否有效时，我们总是在渲染函数中注释掉一些代码并绘制其他东西，我们也可以测试程序是否在没有任何绘图的情况下工作代码，然后我们忘记了取消注释绘图代码，这导致屏幕上没有任何显示。刚开始学习D3D的时候就遇到过这个问题。