分辨率（2048x2048）
// 如果編程使用D3D渲染，請打開下面的設(shè)置，不然各個貼圖接縫處有毛邊。
// Clamp texture, don't wrap (otherwise edges can get filtered)
pd3dDevice->SetSamplerState(0, D3DSAMP_ADDRESSU, D3DTADDRESS_CLAMP);
pd3dDevice->SetSamplerState(0, D3DSAMP_ADDRESSV, D3DTADDRESS_CLAMP);
make skybox yourself:
Just set the FOV to 90, and rotate 90 deg in all directions and that's it.
FOV has to be 90 deg for the camera or it won't work right with a cube.
