So, you know how in some games you can bump the resolution up to 4K(3840 x 2160)? Well, if you only have a 1080 x 1920 screen resolution how does it scale the screen resolution to 4K?
You shouldn’t be able to set the resolution higher than the native resolution of your screen, it can’t actually properly display resolutions higher than that. What you can do though is something called supersampling, where it renders at a higher resolution internally but scales it down to the native resolution of your screen. This helps with anti-aliasing and it’s usually a different setting called something like screen percentage or screen scaling.
Oh okay, well that’s good to know. So, should I even bother with setting resolution to 4K when gaming?
No, most games will check the list of supported resolutions on your display and restrict the list to that. If the game is showing the option then you shouldn’t set it to that since it’ll lower performance. Same for framerate–it’s best to restrict the maximum framerate to the rate that your monitor supports (usually 60hz).
Nvidia DSR and AMD VSR will let you set a 1080p monitor to 4k and super sample everything (including the desktop) for you.
Many modern games, and UE4, have resolution scaling which allows you to put percentage for the game to render at, in relationship to your display resolution. 200% resolution scaling would be 4k on a 1080p monitor. 50% would be 540p.