An argument for Tuned Bicubic and not FSR for scaling

[Vornir]

Im going to preface this with the fact that im not doing this using lossless scaling but with Magpie though i still think this is a relevant thing to talk about. FSR tends to be a go to in gamescope/lossless scaling/magpie for many because its familiar and they have been told "is the best option" (ignoring LS1 for the moment)

Im here to argue that as not being exactly true with an example. FSR is a great scalar and does a fantastic job of using a lanczos like algorithm without having much ringing (it still has some). My problem stems from some of the artifacts that come from using it, namely corner rounding/shape preservation which is something i find extremely annoying. These are likely mitigated by using it in engine but as a scalar for the entire window we have to deal with these.

Take a look here, this is a slightly exaggerated example just to make it obvious. Both bicubic and fsr are using the exact same sharpening pass with the same settings.

Bicubic is setup with values of B = 0.5 and C = 0.25, i picked these after a bunch of A/B compares to minimize ringing absolutely as much as possible on Bicubic while sacrificing some sharpness which we recover some in the sharpen pass. Using a Catmull-Rom bicubic is straight up worse that FSR just for the record, it has far more artifacts.


Here is FSR
https://ibb.co/L066KNP

Tuned Bicubic
https://ibb.co/M27jvZp


You will notice that the bicubic is not as sharp as the FSR, this is both a strength and a weakness IMO but that is going to depend on your sharpness preference. The Bicubic does 2 things much better here, shape preservation and i cannot see any noticeable ringing artifacts in the image. FSR not only rounds the corners on the numbers and distorts the + shape but it has more ringing that the bicubic if you look at the / symbol for instance or on the edges of the battery and the number 2. Thats on top of being slower than the bicubic scaling also.


TLDR: Dont just use any scalar blindly, if you want good quality you need to consider what artifacts you prefer, speed you need, and how much you are scaling. FSR isnt always good and Bicubic is much better than people tend to think it is.