Please redirect me if this is not the right place to ask.
I was unable to find a straightforward answer to this question. What I am wondering is, if I am playing a 1080p game on a 1440p display, what values will be actually displayed on the screen?
A very simplistic solution would be some form of interpolation, like bicubic. Seems reasonable enough, but is it actually what they do? What if I am playing a 1080p game on a 2160p screen (factor of 2)? Is there any significant difference between integer and non-integer scaling factors?
What if I am forcing the game to render more pixels than the display can show, which some games allow (run the game at 1440p but connect a 1080p display). You can set the render scale to 133%. If you do something like this, the rendered image will have more pixels and more fidelity, but almost none of them will have a 1:1 correspondence to the display. You could still interpolate the 1080p pixel values based on a 1440p rendered image, but intuitively, this seems like a huge disadvantage, but when you do this in practice, the image indeed looks better than when you have 100% render scale where every displayed pixel has a 1:1 correspondence to the rendered image.
If I rendered 2160p and displayed this on a 1080p screen, you could average every 2x2 pixels and display it on a single pixel, this seems simple enough, but is it actually what is done or is it indeed optimal?
Essentially I am asking if there is any genius trick to upresing and downresing images
Another heuristic question: Which would look better? A native 1080p 27" screen displaying a 1080p game, or a 1440p 27" screen displaying a 1080p game? Surely the native 1080p screen must look better? But by how much?