stackoverflow找到的方法：http://stackoverflow.com/questions/11714298/d3dxvec3project-requiring-half-the-object-position/11762956#11762956
昨天试了好几种方法，都无效，也许是我笨吧。。。
简单的来说，根据世界坐标系中点的位置利用D3DXVec3Project函数，找到屏幕中该点的投影位置，然后在该位置绘制字体。
1 D3DXVECTOR3 CMFC_D3DView::ToScreenSpace(D3DXVECTOR3 position) 2 { 3 D3DXVECTOR3 out; 4 D3DVIEWPORT9 view; 5 D3DXMATRIX matView; 6 D3DXMATRIX matWorld; 7 D3DXMATRIX matProj; 8 D3DXMATRIX worldPos; 9 D3DXMATRIX worldRotX; 10 D3DXMATRIX worldRotY; 11 D3DXMATRIX worldRotZ; 12 D3DXMATRIX worldScl; 13 14 _device->GetViewport(&view); //view in debug is showing all the correct values. 15 _device->GetTransform(D3DTS_VIEW, &matView); //view is set each frame from the camera 16 _device->GetTransform(D3DTS_PROJECTION, &matProj); //this is set once in the scene manager 17 D3DXMatrixIdentity(&matWorld); 18 //D3DXMatrixTranslation(&matWorld, position.x, position.y, position.z); //uses the given position for the world matrix 19 20 D3DXVec3Project(&out, &position, &view, &matProj, &matView, &matWorld); 21 22 return out; 23 }
stacoverflow中题主出现的问题是显示字体的位置和预想中的不一样，原因就是他改变了世界矩阵matWorld，因为D3DVec3Project函数第二个参数就已经指定点的位置了，所以输入的世界坐标矩阵应该为单位矩阵才不会出现error，所以我就将matWorld单位化了一下，然后在画点的循环中添加
1 D3DXVECTOR3 pOut; 2 D3DXVECTOR3 pIn = D3DXVECTOR3(m_pointList[i].x,m_pointList[i].y,m_pointList[i].z); 3 pOut = ToScreenSpace(pIn); 4 SetRect( &rc, pOut.x,pOut.y, pOut.x+150,pOut.y+100 ); 5 m_pFont->DrawTextA(0, "Hello World", -1, &rc, 0, WHITE);
完整的代码是这样的
1 void CMFC_D3DView::DrawPointUsingSphere() 2 { 3 4 _device->BeginScene(); 5 for (int i = 0;i<m_pointList.size();i++) 6 { 7 _device->SetMaterial(&RED_MTRL); 8 _device->SetTransform(D3DTS_WORLD,&m_MatrixOfPoint[i]); 9 m_ObjectOfPoint[i]->DrawSubset(0);//画球（我是用球代替的点） 10 11 12 D3DXVECTOR3 pOut; 13 D3DXVECTOR3 pIn = D3DXVECTOR3(m_pointList[i].x,m_pointList[i].y,m_pointList[i].z); 14 pOut = ToScreenSpace(pIn); 15 SetRect( &rc, pOut.x,pOut.y, pOut.x+150,pOut.y+100 ); 16 m_pFont->DrawTextA(0, "Hello World", -1, &rc, 0, WHITE);//显示文本 17 18 19 20 21 } 22 _device->EndScene(); 23 24 25 }