爲場景增添光照效果

 基於上一篇文章的框架，寫了個增加光照效果的程序。

先貼一下代碼:

1. //////////////////////////////////////////////////////////////////////////////////////////////////
2. //
3. // File: light.cpp
4. // by tianzhihen 
5. // 2008.10.13
6. // MSVC++ 8.0
7. //////////////////////////////////////////////////////////////////////////////////////////////////
10. #include "d3dUtility.h"
13. //
14. //  全局變量
15. //
17. IDirect3DDevice9* Device = 0;
19. const int Width  = 640;
20. const int Height = 480;
22. // 金字塔頂點緩存 
23. IDirect3DVertexBuffer9* Pyramid = 0;
25. //
26. // 類和結構體
27. //
29. struct Vertex 
30. {
31.     Vertex(){}
32.     Vertex(float x,float y,float z,float nx,float ny,float nz)
33.     {
34.         _x = x; _y = y; _z = z;
35.         _nx = nx; _ny = ny; _nz = nz;
36.     }
37.     float _x,_y,_z;
38.     float _nx,_ny,_nz;  //頂點法向量
39.     static const DWORD FVF;
40. };
42. const DWORD Vertex::FVF = D3DFVF_XYZ | D3DFVF_NORMAL;
45. //
46. // 框架函數
47. //
49. bool Setup()
50. {
51.     //
52.     // 打開光照開關
53.     //
54.     Device->SetRenderState(D3DRS_LIGHTING,true);
56.     //
57.     // 創建頂點/索引緩存
58.     //  
60.     Device->CreateVertexBuffer(
61.         12*sizeof(Vertex),  //注意是12個頂點
62.         D3DUSAGE_WRITEONLY, // 只寫
63.         Vertex::FVF,
64.         D3DPOOL_MANAGED,
65.         &Pyramid,
66.         0);
68.     //
69.     // 用金字塔頂點數據填充緩存
70.     //
72.     Vertex* v;
73.     Pyramid->Lock(0,0,(void**)&v,0);
74.         
75.     // front face
76.     v[0] = Vertex(-1.0f, 0.0f, -1.0f, 0.0f, 0.707f, -0.707f);
77.     v[1] = Vertex( 0.0f, 1.0f,  0.0f, 0.0f, 0.707f, -0.707f);
78.     v[2] = Vertex( 1.0f, 0.0f, -1.0f, 0.0f, 0.707f, -0.707f);
80.     // left face
81.     v[3] = Vertex(-1.0f, 0.0f,  1.0f, -0.707f, 0.707f, 0.0f);
82.     v[4] = Vertex( 0.0f, 1.0f,  0.0f, -0.707f, 0.707f, 0.0f);
83.     v[5] = Vertex(-1.0f, 0.0f, -1.0f, -0.707f, 0.707f, 0.0f);
85.     // right face
86.     v[6] = Vertex( 1.0f, 0.0f, -1.0f, 0.707f, 0.707f, 0.0f);
87.     v[7] = Vertex( 0.0f, 1.0f,  0.0f, 0.707f, 0.707f, 0.0f);
88.     v[8] = Vertex( 1.0f, 0.0f,  1.0f, 0.707f, 0.707f, 0.0f);
90.     // back face
91.     v[9]  = Vertex( 1.0f, 0.0f,  1.0f, 0.0f, 0.707f, 0.707f);
92.     v[10] = Vertex( 0.0f, 1.0f,  0.0f, 0.0f, 0.707f, 0.707f);
93.     v[11] = Vertex(-1.0f, 0.0f,  1.0f, 0.0f, 0.707f, 0.707f);
95.     Pyramid->Unlock();
97.     //
98.     // 創建/設置 材質 
99.     //
101.     D3DMATERIAL9 mtrl = d3d::InitMtrl(d3d::WHITE,d3d::WHITE,d3d::WHITE,d3d::BLACK,5.0f);
102.     Device->SetMaterial(&mtrl);
104.     //
105.     // 創建方向光
106.     //
108.     D3DXCOLOR lc = d3d::WHITE;
109.     D3DLIGHT9 dir = d3d::InitDirectionalLight(&D3DXVECTOR3(1.0f,0.0f,0.0f),&lc);
111.     Device->SetLight(0,&dir);
112.     Device->LightEnable(0,true);
114.     //
115.     // 啓用鏡面高光,並規範化法向量
116.     //
118.     Device->SetRenderState(D3DRS_NORMALIZENORMALS,true);
119.     Device->SetRenderState(D3DRS_SPECULARENABLE,true);
121.     //
122.     // 創建取景變換矩陣
123.     //
125.     D3DXVECTOR3 position(0.0f,0.0f,-3.0f);
126.     D3DXVECTOR3 target(0.0f,0.0f,0.0f);
127.     D3DXVECTOR3 up(0.0f,1.0f,0.0f);
128.     D3DXMATRIX V;
129.     D3DXMatrixLookAtLH(&V,&position,&target,&up);
131.     Device->SetTransform(D3DTS_VIEW,&V);
133.     //
134.     // 設置投影矩陣
135.     //
137.     D3DXMATRIX proj;
138.     D3DXMatrixPerspectiveFovLH(
139.                 &proj,
140.                 D3DX_PI*0.5f,
141.                 (float)Width/(float)Height,
142.                 1.0f,
143.                 1000.0f);
144.     Device->SetTransform(D3DTS_PROJECTION,&proj);
146.     return true;
147. }
150. void Cleanup()
151. {
152.     d3d::Release<IDirect3DVertexBuffer9*>(Pyramid);
153. }
156. bool Display(float timeDelta)
157. {
158.     if (Device)
159.     {
160.         //
161.         // 旋轉矩陣
162.         //
164.         D3DXMATRIX yRot;
166.         // 繞 y 方向每幀遞增角度
167.         static float y = 0.0f;
168.         D3DXMatrixRotationY(&yRot,y);
169.         y += timeDelta;
171.         // 角度達到360度後歸零
172.         if (y>=6.28f)
173.         {
174.             y = 0.0f;
175.         }
177.         Device->SetTransform(D3DTS_WORLD,&yRot);
179.         //
180.         // 繪製場景
181.         //
183.         Device->Clear(0,0,D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER , 0xffffffff,1.0f,0);
184.         Device->BeginScene();
186.         Device->SetStreamSource(0,Pyramid,0,sizeof(Vertex));
187.         Device->SetFVF(Vertex::FVF);
189.         // 繪製4個三角形圖元
190.         Device->DrawPrimitive(D3DPT_TRIANGLELIST,0,4);
192.         Device->EndScene();
194.         Device->Present(0,0,0,0);
195.     }
197.     return true;
198. }
200. //
201. // WndProc
202. //
204. LRESULT CALLBACK d3d::WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam )
205. {
206.     switch(msg)
207.     {
208.     case WM_DESTROY:
209.         ::PostQuitMessage(0);
210.         break;
212.     case WM_KEYDOWN:
213.         if(wParam == VK_ESCAPE)
214.             ::DestroyWindow(hwnd);
215.         break;
216.     }
218.     return ::DefWindowProc(hwnd,msg,wParam,lParam);
220. }
222. //
223. //  WinMain
224. //
226. int WINAPI WinMain(HINSTANCE hInstance,
227.                    HINSTANCE hPrevInstance, 
228.                    LPSTR lpCmdLine,
229.                    int nShowCmd )
230. {
231.     //程序入口地址
233.     //初始化D3D
234.     if (!d3d::InitD3D(hInstance,640,480,true,D3DDEVTYPE_HAL,&Device))
235.     {
236.         ::MessageBox(0, "InitD3D() - FAILED", 0, 0);
237.         return 0;
238.     }
240.     //分配資源
241.     if (!Setup())
242.     {
243.         ::MessageBox(0, "Setup() - FAILED", 0, 0);
244.         return 0;
245.     }
247.     //進入消息循環
248.     d3d::EnterMsgLoop(Display);
250.     //清理資源
251.     Cleanup();
253.     Device->Release();
255.     return 0;
256. }

值得注意的是頂點法向量的計算。這裏金字塔的各頂點的法向量爲此頂點所在三角形面的面法向量。由於同一頂點當處於不同三角形面時的法向量不同，所以這裏創建了12個頂點緩存。

1.     Device->CreateVertexBuffer(
2.         12*sizeof(Vertex),  //注意是12個頂點
3.         D3DUSAGE_WRITEONLY, // 只寫
4.         Vertex::FVF,
5.         D3DPOOL_MANAGED,
6.         &Pyramid,
7.         0);

那麼頂點法向量是如何求得的呢？ 設有3個頂點p0 p1 p2，則 p1 - p0 = u   p2 - p0 = v  則面法線爲 n = u x v (叉乘) 由於各頂點的法向量與面法線相同，所以 n0 = n1 = n2 = n

例如對於front面

 // front face
 v[0] = Vertex(-1.0f, 0.0f, -1.0f, 0.0f, 0.707f, -0.707f); //設爲p0
 v[1] = Vertex( 0.0f, 1.0f,  0.0f, 0.0f, 0.707f, -0.707f); //設爲p1
 v[2] = Vertex( 1.0f, 0.0f, -1.0f, 0.0f, 0.707f, -0.707f); //設爲p2

p1 - p0 = u =(1,1,1)   p2 - p0 = v =(2,0,0)    n = u x v =(1,1,1) x (2,0,0) =(0,2,-2) (ps:這個不用我說了吧,不知道的google去) 單位化之則面法線爲 n = ( 0.0f, 0.707f, -0.707f)  同理可得其他。

 

附圖: