OpenGL和D3D

作為一個3D程式員, 我用了OpenGL兩年多, 最近在搞一個項目, 從OpenGL轉到D3D, 雖然工程外在的架構都封裝得不錯, 但想完全地從OpenGL轉換到D3D, 看起來還是有難度的, 花了我兩個星期的時間, 我終於轉換過來了。
D3D與OpenGL的幾點比較明顯不同的地方:
(一)、正交投影時：OpenGL以螢幕左上方為(0,0), 而D3D卻以螢幕中心為(0,0)
(二)、OpenGL使用右手座標系， 而D3D使用左手座標系
(三)、OpenGL使用旋轉操作等轉入的角度參數是 角度, 而D3D是 弧度，所以注意要PI * Angle / 180

下面我把具體地API對照關係列出來(不是很全，以後添加中.......)

1. 座標變換
pos = D3DXVECTOR3(0,2,-1.5);
at = D3DXVECTOR3(0,0,0);
up = D3DXVECTOR3(0,1,0);
D3DXMatrixLookAtLH(&view,&pos,&at,&up);
pd3dDevice->SetTransform(D3DTS_VIEW,&view);

2. 繪製
pd3dDevice->SetRenderState(D3DRS_FILLMODE,D3DFILL_WIREFRAME);

    DrawPrimitive()
DrawIndexedPrimitive()

DrawPrimitiveUP()
DrawIndexedPrimitiveUP()
3. 顏色

4. 片段測試

(1) 深度測試
g_pDevice->SetRenderState(D3DRS_ZENABLE, TRUE);            //glEnable(GL_DEPTH_TEST);  
g_pDevice->SetRenderState(D3DRS_ZFUNC, D3DCMP_LESSEQUAL);     //glDepthFunc(GL_LEQUAL);
//--------------------------------------------------------------------------------------------------------
g_pDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_CCW);       //glEnable(GL_CULL_FACE);

(2) Alpha測試
//--------------------------------------------------------------------------------------------------------
g_pDevice->SetRenderState(D3DRS_ALPHATESTENABLE, TRUE);                //glEnable(GL_ALPHA_TEST);
g_pDevice->SetRenderState(D3DRS_ALPHAFUNC, D3DCMP_GREATER);     //glAlphaFunc(GL_GREATER, 0.1f);
g_pDevice->SetRenderState(D3DRS_ALPHAREF, 0.1 * 255); //取值範圍 0 ~ 255

(3) 剪裁測試 (平面剪下)
//--------------------------------------------------------------------------------------------------------
// Enable clip plane for reflection map
CMatrix44f pWorldViewProjIT=m_pWorldViewProj;
//pWorldViewProjIT.Transpose();
pWorldViewProjIT.Invert();   

// Transform plane to clip-space
float pClipSpacePlane[4];
float pClipPlane[]= { 0, 0, 1, 0};   

// Check if camera is below water surface, if so invert clip plane
CVector3f pEye=(CVector3f)m_pCamera.GetPosition();
if(-pEye.m_fZ<0.0)
{
   pClipPlane[2]=-pClipPlane[2];
}

MatrixTransformPlane(pClipSpacePlane, pClipPlane, pWorldViewProjIT);

// enable clip plane now
g_pDevice->SetClipPlane(0, pClipSpacePlane);  
g_pDevice->SetRenderState(D3DRS_CLIPPLANEENABLE, 1);

(4) 模板測試
//--------------------------------------------------------------------------------------------------------
g_pDevice->SetRenderState(D3DRS_STENCILENABLE, TRUE);
    g_pDevice->SetRenderState(D3DRS_STENCILFUNC, 3DCMP_ALWAYS);
    g_pDevice->SetRenderState(D3DRS_STENCILREF, 0x1); //取值範圍 0 ~ 255
   
    Device->SetRenderState(D3DRS_STENCILPASS, D3DSTENCILOP_KEEP);

5. 紋理操作

g_pDevice->SetSamplerState( 0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
g_pDevice->SetSamplerState( 0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);
g_pDevice->SetSamplerState( 0, D3DSAMP_MIPFILTER, D3DTEXF_LINEAR);

g_pDevice->SetSamplerState( 0, D3DSAMP_ADDRESSU, D3DTADDRESS_CLAMP);
   g_pDevice->SetSamplerState( 0, D3DSAMP_ADDRESSV, D3DTADDRESS_CLAMP);

6. 緩衝區操作
  
(1) 顏色緩衝
//--------------------------------------------------------------------------------------------------------
g_pDevice->SetRenderState(D3DRS_COLORWRITEENABLE, D3DCOLORWRITEENABLE_ALPHA);
g_pDevice->SetRenderState(D3DRS_COLORWRITEENABLE, 0x000000F);

(2) 深度緩衝
//--------------------------------------------------------------------------------------------------------
g_pDevice->SetRenderState(D3DRS_ZENABLE, TRUE);            //glEnable(GL_DEPTH_TEST);
g_pDevice->SetRenderState(D3DRS_ZWRITEENABLE, TRUE);         //glDepthMask(GL_TRUE);

(3) 模板緩衝
//--------------------------------------------------------------------------------------------------------

(4) 渲染到紋理
//--------------------------------------------------------------------------------------------------------
// Render targets
IDirect3DSurface9 *m_plD3DBackbufferSurf,
   *m_plD3DDepthStencilSurfAA,
   *m_plD3DDepthStencilSurf;

CRenderTarget *m_pRTRefraction, *m_pRTReflection; //(自訂紋理類)

//-----------------------------------------------------------------------------------

// Get backbuffer
g_pDevice->GetRenderTarget(0, &m_plD3DBackbufferSurf);

// Get depthstencil
g_pDevice->GetDepthStencilSurface(&m_plD3DDepthStencilSurfAA);

// Restore previous states
g_pDevice->SetRenderTarget(0, m_plD3DBackbufferSurf);
g_pDevice->SetDepthStencilSurface(m_plD3DDepthStencilSurfAA);

// (1)折射圖--------------------------------------------------------------------------

//下面的語句調用了 g_pDevice->CreateRenderTarget(iWidth, iHeight, (D3DFORMAT) iFormat, (D3DMULTISAMPLE_TYPE)iAASamples, 0, 0, &m_plD3Surf, 0));
if(FAILED(m_pRTRefraction->Create(m_fWidth>>1, m_fHeight>>1, D3DFMT_A8R8G8B8)))
{
   return APP_ERR_INITFAIL;
}

// Create depthstencil withouth multisampling
g_pDevice->CreateDepthStencilSurface(m_fWidth, m_fHeight, D3DFMT_D24X8, (D3DMULTISAMPLE_TYPE)0, 0, 0, &m_plD3DDepthStencilSurf, 0);

g_pDevice->SetRenderTarget(0, m_pRTReflection->GetSurface());

g_pDevice->StretchRect(m_plD3DBackbufferSurf, 0, m_pRTRefraction->GetSurface(), 0, D3DTEXF_NONE);

// (2)反射圖-----------------------------------------------------------------------------------
m_pRTReflection=new CRenderTarget;
if(FAILED(m_pRTReflection->Create(m_fWidth>>2, m_fHeight>>2, D3DFMT_A8R8G8B8)))
{
   return APP_ERR_INITFAIL;
}

g_pDevice->SetRenderTarget(0, m_pRTReflection->GetSurface());

//-----------------------------------------------------------------------------------
g_pDevice->SetRenderTarget(0, m_pRTReflection->GetSurface());
g_pDevice->SetDepthStencilSurface(m_plD3DDepthStencilSurf);
g_pDevice->Clear(0, 0, D3DCLEAR_TARGET|D3DCLEAR_ZBUFFER, D3DCOLOR_ARGB(255, 0, 0, 128), 1.0f, 0);  
SetViewport(m_pRTReflection->GetWidth(), m_pRTReflection->GetHeight());
//-----------------------------------------------------------------------------------

D3DXSaveTextureToFile("imageTex.jpg",D3DXIFF_JPG,(IDirect3DTexture9*)m_pWavesBump->GetTexture(),NULL);

7. 混合操作
g_pDevice->SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE);     //glDisable(GL_BLEND);
g_pDevice->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);   //glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
g_pDevice->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);

8. 燈光與材質
g_pDevice->SetRenderState(D3DRS_LIGHTING, FALSE); //glDisable(GL_LIGHTING);

D3DMATERIAL9 mtrl;
mtrl.Ambient = a;
mtrl.Diffuse = d;
mtrl.Specular = s;
mtrl.Emissive = e;
mtrl.Power    = p;
Device->SetMaterial(&mtrl); //在設定紋理前設定
//設定當前使用的紋理