Initiate the rendering of a cubic environment map.
HRESULT BeginCube( LPDIRECT3DCUBETEXTURE9 pCubeTex );
If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be D3DERR_INVALIDCALL.
See ID3DXRenderToEnvMap::Face to draw each of the 6 faces.
Header: Declared in D3dx9core.h.