I'm currently evaluating to buy a 4K computer screen to use in 2160p natively while coding or working with Windows but I plan to play my games in 1080p because 4K rendering is of course a very heavy job to do for any CPU&GPU. Currently I'm very happy with 1080p gaming and it would be great for me to have one single screen in those two modes.
However, I know that the upscaling algorithms are not just "1px in 1080p equals 2x2px in 2160p – so everything would be fine …" as it is told in many forums. That's just wrong because normally the screen image gets blurred depending on the upscaling algorithms the GPU and/or the screen are applying.
Now, I stumbled upon nvidia's Dynamic Super Resolution technology and I wondered (but I could not really find out) whether it (or any other tech) can be used to tell the GPU to render a 2160p image exactly by bloating up a 1080p image to the doubled size per side . So that there's no need to interpolate any pixels and the 2160p-image would just look as crisp as the 1080p on a 1080p-screen (of course with the same non-4K-amount of detail).
Please have a look at the attached image I have stolen from http://linustechtips.com/ and extended with my comments:
EDIT: I know that DSR is supposed to perform downsampling high-res images to a lower-res screen. So it is the opposite of what I wanted to have. But maybe the nvidia driver can do the other way round as well (maybe it's not called DSR then but I don't know).
Best Answer
The DSR article is about a 1080 display benefitting from 4K rendering, which is the opposite of your use case.
The image is a fair idea, except that 1080 is 1920x1080 and 4k is 4096x2160. 4096/2 is NOT 1920.
For gaming, you're just going to want to use the monitor's native resolution so that the monitor doesn't tamper with the image.
Certain displays are able to do the pixel doubling.
That's the feature you're looking for: "pixel doubling". Stay away from bilinear or bicubic scaling.