This allows you to set the user interface to native resolution, and then pick a percentage value of chosen resolution for rendering the 3D image.
The game currently does not support downsampling. If you want to render at a higher resolution than your screens native, you'll need to change your Windows desktop resolution. This is an undesired workaround, and doesn't work very well.
My monitor is 1080p. If I set my desktop resolution to 2160p, then in-game the only option inbetween is 1440p. And this still renders the entire game, UI and all, at that resolution.
If we could set a render-scale with 10% stops up to 200%, and down to 50%, everyone would be able to optimise their game far better.
The game already clearly support arbitrary resolutions, as you can manipulate the windowed-mode and always get a pixel-perfect image. And this feature is becoming standard in many AAA games, like Overwatch, and Gears of War 4, a fellow Xbox Play Anywhere title.
Got a powerful computer? You can improve image clarity by increasing it until your framerate drops.
Got a lower spec PC? You can render at a lower resolution but still have clean and crisp menus and UI.
