I've been running into quite a few performance issues with my game lately, especially on integrated GPU's, and most of them are solved by heavily reducing resolution of the game (i.e. changing fullscreen scaling to low quality, then scaling the canvas down while keeping the window the same size). This leads me to assume that GPU fillrate is the primary issue.
For those unfamiliar, AFAIK fillrate is simply the amount of pixels the GPU has to draw - at higher window sizes this increases exponentially and can be very straining if you have a lot of layers of content, as I do in my game.
A great solution to this issue would be being able to render objects/layers at a smaller resolution, then having the engine do a cheap scale-up. Many layers, e.g. backgrounds, and many objects, e.g. full-screen overlays, do not need to be drawn at full scale resolution all the time. Currently there's no way to do even a simple fade-to-black effect without a complete screen of pixel fill. Over 50% of my layers could easily get away with a significant resolution reduction and the performance implications (especially when you consider shaders) would be huge.
I believe that this could also possibly help performance on mobile devices, something I'm not personally concerned with but I know many are.
Is this something that's technically impossible to do in the engine?
Does anyone else agree that this is an important feature to have?