VRay VFB Viewport Loader
This will load grab your current viewport and put it as a background for your VRay. Really useful for when you want to do a region render in the VFB but don't know where to draw your region. It's clever enough to crop to your safe-frames, and resize to your render size, upscaling to large resolutions won't give you the best quality but should hopefully help!
Run the mcr file, as you would a script file, then go to
Customize -> Customize User Interface, choose to assign it to a hotkey or menu or toolbar and find the tool under 'DW Tools'
Updated to work with VRayRT properly