No problems with DX11 on a vbox virtual machine, like I said, if you enable 3D acceleration it work well... If your virtualized OS have access to a compliant GPU, then, virtualized Windows will have a working DX11, no matter of the virtualization software, only important thing is 3D acceleration.
BitMaster is true, there are not any step-to-step to do this result but it is not complicated (this part) :
- Depending of your distribution, install gnome like that : apt-get install ubuntu-gnome-desktop
- For NoMachine (I use it to take remote control on Gnome) : https://www.nomachine.com/all-documents
And this is just a first step. Next steps are a bit more complicated, you'll have to manage network access to/from the virtual machine and that depend of many things (numbers of NICs, possibility to have a secondary IP and so on.