High-fps monitors: good for Doom?

I was just thinking about frame rate stuff and how a general move to higher-FPS monitors would actually end up making Doom look a little smoother.

Doom ran at 35hz, and was displayed on a monitor running at 70hz. Each frame was (obviously) supposed to be displayed for the same length of time, giving the whole thing a consistent appearance.

However, most modern computers run at 60hz, which is unfortunately not an exact multiple of 35. So frames need to be displayed for variable lengths of time in order for things to stay in sync, and this judder can sometimes be noticeable.

One thing higher-fps monitors can do (especially 144hz ones) is smooth out the frame time to be practically the same as it was back on a DOS CRT. Here's an approximation of a 35hz signal being displayed on monitors of different fps:

- 35hz (also 70hz, 105, etc)
- 60hz
- 90hz (what VR headsets are running at)
- 120hz
- 144hz

Another option, of course, is to utilize G-Sync or Freesync to drive the monitor at 70hz (or 105, or 140) in order to get perfect frame timings for Doom.

Anyways, I have nothing useful to contribute or anything, but I was just thinking about this and figured I would write it down for future reference.

That's what frame interpolation is there for. If that is properly implemented 60 Hz are not a problem.

With higher refresh rates a far more important problem is that unless you are using very simple levels, the renderer cannot keep up with the monitor.

Graf Zahl said:

That's what frame interpolation is there for. If that is properly implemented 60 Hz are not a problem.

You know perfectly well I am specifically talking about playing the game at 35hz, not with interpolation, but thanks for bringing it into this thread anyway.

I have a 120 Hz monitor and reasonably sensitive eyes (I can tell the difference between 110 and 120 Hz quite comfortably). I normally play at 120 Hz so after seeing this post I thought I'd try 70 as a multiple of 35. I was hard pressed to tell any difference between the two, certainly not to pass a double blind trial of any sort. At the very least 70 didn't seem worse than 120.

I went back and tried 60 out of interest. At least on my monitor, the difference between 120 and 60 is barely (if at all?) noticeable. Definitely not as noticeable as a difference between refresh rates with an appropriately high frame rate on my setup. I wouldn't be confident picking out 35 FPS@60 Hz versus 35FPS@120 Hz.

I don't have the sharpest eyes and my setup won't replicate everyone's experience of course. I remember with Quakeworld capping your FPS at different numbers above your refresh rate did have an effect on smoothness (and on or near an integer multiple tended to be the best) which is pretty much what's happening here: the out of step nature of two different updating systems.

What those higher FPS monitors do is causing a sort of framerate ripple, as not all frames have equal duration anymore. It's comparable to periodic wow & flutter on a warped record, or to an aural beat between two close but slightly out of phase events. I wouldn't be surprised if some people found them annoying or even nausea inducing, but to notice them you'd need very particular conditions (e.g. a static scene with only scrolling fextures, crossing a very long featureless hallway at a fixed course and speed, etc.)

Ripple is a great way of describing it, considering it is analagous to interference between two out of phase waves.

My understanding is G-Sync monitors will actually refresh as low as 30hz, after that it will switch to v-sync. The built in framerate meter on my G-Sync display seems to indicate that it is refreshing at 35hz when I cap the framerate in ZDoom, with no tearing or judder that I can perceive. Feels nice.

As such G-Sync seems like it would be beneficial for Doom even on 60hz panels (such displays that are equipped with G-Sync are often ultra wides at higher resolutions or laptops where 60hz is usually as good as it gets.)

I don't know if it has anything to do with G-sync, the monitor supporting it or not (I don't really follow this stuff, don't care about modern PC games and especially I don't really take games way too seriously anymore), but after I saw Ling commenting on that other thread about Doom having been coded to use a 70Hz rather than 60Hz video mode being actually a bad thing on grounds of causing problems in modern days when 60Hz has become a standard, I had to ask a guy I know who bought a 144Hz gaming display some time ago (the display is something from Asus, I don't remember the model) whether it's possible to use eg. Nvidia's control panel utility to add custom video modes with a 70Hz or 140Hz refresh rate and use it for Doom. He tried it and said that yeah, it's possible and works fine.

I was going to post about this into that other thread but forgot about it, heh.

High framerate monitors are all kinds of great. Used one for testing/development here, I need one for myself now (and a 4K monitor, but that's another story...)

In terms of responsiveness with Doom, it won't help with the core input routine locked to 35Hz but it'll smooth out the visuals since 35 divides in to, say, 144Hz far nicer than it divides in to 60Hz.

GooberMan said:

High framerate monitors are all kinds of great. Used one for testing/development here, I need one for myself now (and a 4K monitor, but that's another story...)

So true. Even just dragging windows around is visibly smoother. Playing fast-paced games at 120 FPS/Hz is just a pleasure.

i have an acer xb270hu, 144 hz g-sync or 120 hz ulmb. i guess ulmb is more useful for doom as a steady frame rate can be held, but it makes the screen darker. it's very responsive. the only problem with it is that red is so intense , i can't see much after getting hit. 60 hz is a thing of the past.