关于DX中三角形的构造顺序

 今天写了一个简单的程序，显示一个三角形，结果就是看不到在屏幕上，我构造的三角形如下：

1.     vertices[0].position = D3DXVECTOR3(150.0f,  50.0f, 1.0f);//三个点
2.     vertices[0].rhw      = 1.0f;
3.     vertices[0].color    = 0xffff0000;
4.     vertices[1].position = D3DXVECTOR3(50.0f, 220.0f, 1.0f);//注意这行的变化
5.     vertices[1].rhw      = 1.0f;
6.     vertices[1].color    = 0xff0000ff;
7.     vertices[2].position = D3DXVECTOR3(250.0f, 250.0f, 1.0f);//注意这行的变化
8.     vertices[2].rhw      = 1.0f;
9.     vertices[2].color    = 0xffffffff;

应当说是一个简单的程序，可为什么会显示不出来呢？我把顶点又改成下面：

1.     vertices[0].position = D3DXVECTOR3(150.0f,  50.0f, 1.0f);//三个点
2.     vertices[0].rhw      = 1.0f;
3.     vertices[0].color    = 0xffff0000;
4.     vertices[1].position = D3DXVECTOR3(250.0f, 220.0f, 1.0f);//注意这行的变化
5.     vertices[1].rhw      = 1.0f;
6.     vertices[1].color    = 0xff0000ff;
7.     vertices[2].position = D3DXVECTOR3( 50.0f, 250.0f, 1.0f);//注意这行的变化
8.     vertices[2].rhw      = 1.0f;
9.     vertices[2].color    = 0xffffffff;

结果还被我试出来了，屏幕上显示一个三角形。由于以前三角形的顶点是随便写的，后来在纸上一画，立即明白了道理：我以前那个三角形是反时针构造的，而DX中的三角形是顺时针构造的，明白了这个道理，我立即想到了背景剔除。然后我又用前面的三角形，不过我关闭背景剔除功能，结果也能显示出来了：

1.     vertices[0].position = D3DXVECTOR3(150.0f,  50.0f, 1.0f);//三个点
2.     vertices[0].rhw      = 1.0f;
3.     vertices[0].color    = 0xffff0000;
4.     vertices[1].position = D3DXVECTOR3(50.0f, 220.0f, 1.0f);
5.     vertices[1].rhw      = 1.0f;
6.     vertices[1].color    = 0xff0000ff;
7.     vertices[2].position = D3DXVECTOR3(250.0f, 250.0f, 1.0f);
8.     vertices[2].rhw      = 1.0f;
9.     vertices[2].color    = 0xffffffff;
10.     g_pD3DDev->SetRenderState(D3DRS_CULLMODE, D3DCULL_NONE);

不过这时候看到的三角形是他的反面！

 

顺便赋些代码：

1. /******************************************************
2. FileName: CTDUIMessage.h   - TDOnline/UISystem
3. Author: lsm   Version:        Date: 08/11/4
4. Description: 索引缓冲区的使用
5. History:
6. <author>  <time>  <version>  <note>
8. ******************************************************/
10. /*-------------Head------------*/
11. #include "assert.h"
12. #include "d3dx9.h"
13. #pragma warning(disable : 4996)
14. #include "strsafe.h"
15. #pragma warning(disable : 4996)
17. LPDIRECT3D9                g_pD3DObj   = NULL; //D3D 对象
18. LPDIRECT3DDEVICE9          g_pD3DDev   = NULL; //D3D 设备
19. LPDIRECT3DVERTEXBUFFER9    g_pVerBuf   = NULL; //顶点缓冲区
20. LPDIRECT3DINDEXBUFFER9     g_pInBuf    = NULL; //索引缓冲区
22. TCHAR g_AppName[] = TEXT("D3D");//类名
24. #define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZRHW | D3DFVF_DIFFUSE)//灵活顶点格式
26. struct CUSTOMVERTEX 
27. {
28.     D3DXVECTOR3 position;
29.     float       rhw;
30.     D3DCOLOR    color;
31. };
32. /*---------------End------------*/
35. /*==========================================
36. Function name: InitD3D
37. Description: 初始化D3D对象
38. ==========================================*/
39. HRESULT InitD3D(HWND hWnd)
40. {
41.     if((g_pD3DObj = Direct3DCreate9(D3D_SDK_VERSION)) == NULL)//创建3D对象
42.     {
43.         assert(false);
44.         return E_FAIL;
45.     }
47.     D3DDISPLAYMODE devMode;
48.     if (FAILED(g_pD3DObj->GetAdapterDisplayMode(D3DADAPTER_DEFAULT, &devMode)))//获得显卡信息
49.     {
50.         assert(false);
51.         return E_FAIL;
52.     }
54.     D3DPRESENT_PARAMETERS d3dpp;
55.     ZeroMemory(&d3dpp, sizeof(d3dpp));
56.     d3dpp.Windowed               = true;
57.     d3dpp.SwapEffect             = D3DSWAPEFFECT_DISCARD;
58.     d3dpp.BackBufferFormat       = D3DFMT_UNKNOWN;
60.     if(FAILED(g_pD3DObj->CreateDevice(
61.                                       D3DADAPTER_DEFAULT,
62.                                       D3DDEVTYPE_HAL,
63.                                       hWnd,
64.                                       D3DCREATE_SOFTWARE_VERTEXPROCESSING,
65.                                       &d3dpp,
66.                                       &g_pD3DDev
67.                                       )))
68.     {
69.         assert(false);
70.         return E_FAIL;
71.     }
73.     return S_OK;
74. }
76. /*==========================================
77. Function name: InitVBuf
78. Description: 填充顶点缓冲区
79. ==========================================*/
80. HRESULT InitVBuf()
81. {
82.     if (FAILED(g_pD3DDev->CreateVertexBuffer(
83.                                              3*sizeof(CUSTOMVERTEX),
84.                                              0,
85.                                              D3DFVF_CUSTOMVERTEX,
86.                                              D3DPOOL_DEFAULT,
87.                                              &g_pVerBuf,
88.                                              NULL
89.                                              )))
90.     {
91.         return E_FAIL;
92.     }
94.     CUSTOMVERTEX *vertices;
96.     if (FAILED(g_pVerBuf->Lock(0, 0, (void**)&vertices, 0)))//锁住内存
97.     {
98.         return E_FAIL;
99.     }
101.     vertices[0].position = D3DXVECTOR3(150.0f,  50.0f, 1.0f);//四个点
102.     vertices[0].rhw      = 1.0f;
103.     vertices[0].color    = 0xffff0000;
104.     vertices[1].position = D3DXVECTOR3(50.0f, 220.0f, 1.0f);
105.     vertices[1].rhw      = 1.0f;
106.     vertices[1].color    = 0xff0000ff;
107.     vertices[2].position = D3DXVECTOR3(250.0f, 250.0f, 1.0f);
108.     vertices[2].rhw      = 1.0f;
109.     vertices[2].color    = 0xffffffff;
110.     g_pD3DDev->SetRenderState(D3DRS_CULLMODE, D3DCULL_NONE);
111.     //vertices[3].position = D3DXVECTOR3(250.0f, 250.0f, 0.0f);
112.     //vertices[3].rhw      = 1.0f;
113.     //vertices[3].color    = 0xff000fff;
115.     g_pVerBuf->Unlock();
118.     //WORD indexBuf[] = {0, 1, 2, 0, 2, 3};
119.     //void *pIndex;
120.     //g_pD3DDev->CreateIndexBuffer(sizeof(indexBuf), 0, D3DFMT_INDEX16, D3DPOOL_DEFAULT,&g_pInBuf, NULL);
121.     //g_pInBuf->Lock(0, sizeof(indexBuf), (void **)&pIndex, 0);
122.     //memcpy(pIndex, indexBuf, sizeof(indexBuf));
123.     //g_pInBuf->Unlock();
125.     g_pD3DDev->SetRenderState(D3DRS_CULLMODE, D3DCULL_NONE);
127.     return S_OK;
128. }
131. /*==========================================
132. Function name: Cleanup
133. Description: 释放对象
134. ==========================================*/
135. VOID Cleanup()
136. {
137.     if (g_pVerBuf != NULL)
138.     {
139.         g_pVerBuf->Release();
140.     }
142.     if (g_pD3DDev != NULL)
143.     {
144.         g_pD3DDev->Release();
145.     }
147.     if (g_pD3DObj != NULL)
148.     {
149.         g_pD3DObj->Release();
150.     }
151. }
153. /*==========================================
154. Function name: Render
155. Description: 负责渲染
156. ==========================================*/
157. VOID Render()
158. {
159.     if (g_pD3DDev == NULL)
160.     {
161.         return ;
162.     }
164.     g_pD3DDev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 0, 255), 1, 0);
166.     if (SUCCEEDED(g_pD3DDev->BeginScene()))
167.     {
168.         g_pD3DDev->SetStreamSource(0, g_pVerBuf, 0, sizeof(CUSTOMVERTEX));
169.         g_pD3DDev->SetFVF(D3DFVF_CUSTOMVERTEX);
170.         //g_pD3DDev->SetIndices(g_pInBuf);
171.         //g_pD3DDev->DrawIndexedPrimitive(D3DPT_TRIANGLELIST, 0, 0, 4, 0, 2);
172.         g_pD3DDev->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 1);
174.         g_pD3DDev->EndScene();
175.     }
177.     g_pD3DDev->Present(NULL, NULL, NULL, NULL);
178. }
179. /*==========================================
180. Function name: MsgProc
181. Description: 负责消息循环
182. ==========================================*/
183. LRESULT WINAPI MsgProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
184. {
185.     switch(msg)
186.     {
187.     case WM_DESTROY:
188.         Cleanup();
189.         PostQuitMessage(0);
190.         return 0;
191.     }
193.     return DefWindowProc(hWnd, msg, wParam, lParam);
194. }
196. /*==========================================
197. Function name: WinMain
198. Description: 程序启动函数
199. ==========================================*/
200. INT WINAPI WinMain(HINSTANCE hInst, HINSTANCE, LPSTR, INT)
201. {
202.     WNDCLASSEX wc = {
203.                    sizeof(WNDCLASSEX), 
204.                    CS_CLASSDC, 
205.                    MsgProc, 
206.                    0L, 
207.                    0L, 
208.                    GetModuleHandle(NULL),
209.                    NULL,
210.                    NULL,
211.                    NULL,
212.                    NULL,
213.                    g_AppName,
214.                    NULL
215.                    };
216.     RegisterClassEx(&wc);
218.     HWND hWnd = CreateWindow(
219.                              g_AppName, 
220.                              TEXT("D3D Tutorial 1"), 
221.                              WS_OVERLAPPEDWINDOW, 
222.                              100, 
223.                              100, 
224.                              300, 
225.                              300,
226.                              NULL, 
227.                              NULL, 
228.                              wc.hInstance, 
229.                              NULL 
230.                              );
232.     if (hWnd == NULL)
233.     {
234.         return -1;
235.     }
237.     if(SUCCEEDED(InitD3D(hWnd)))
238.     {
239.         if(SUCCEEDED(InitVBuf()))
240.         {
241.             ShowWindow(hWnd, SW_SHOWDEFAULT);
242.             UpdateWindow(hWnd);
244.             MSG msg;
245.             ZeroMemory(&msg, sizeof(msg));
246.             while (msg.message != WM_QUIT)
247.             {
248.                 if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
249.                 {
250.                     TranslateMessage(&msg);
251.                     DispatchMessage(&msg);
252.                 }
253.                 else
254.                 {
255.                     Render();
256.                 }
257.             }
258.         }
259.     }
261.     UnregisterClass(g_AppName, wc.hInstance);
262.     return 0;
263. }