Why can't 16:9 displays render ultrawide aspect ratios with no black bars?

[TwistedMetalGear]

This may be dumb question, but say you want to run a game at 32:9 on a 16:9 monitor. I'm pretty sure you can set up custom resolutions to do that, but you'd have black bars.

So how come the black bar area can't be unlocked to render more of the game? For instance, in this screenshot, I overlaid a 32:9 image onto a 16:9 background. I'm imagining that the rendering area of the game expand vertically such that there's no more black bars. The end result being something better than ultrawide. Same horizontal FOV as ultrawide but with more vertical FOV.

Am I just describing the FOV option found in most games? I'm pretty sure that option doesn't allow you to achieve results like this.

 

[sharknice]

Yes, it would just be the same thing as increasing the FOV. Essentially doubling the vertical FOV.
Most games don't let you increase it that much, if they even let you adjust it at all.

 

[NattyKathy]

Yah this is just expanded FOV. Aspect ratio and FOV are different things, though wider aspect ratio does usually inherently mean wider FOV.
Cyberpunk 2077 shown in the screenshot can have unlocked FOV with configfile edit- look for FOV mods on Nexusmods dot com.

 

[Okatis]

Ultrawide in this described scenario is only useful if the game lacks native FoV sliders that widen to this degree (IIRC Overwatch for example lacks a dedicated FoV slider but does widen the FoV for ultra wide resolutions). So yeah, what everyone else has mentioned.

I will add though: it can also be useful for performance if the ultrawide aspect ratio matches the same native resolution width of the monitor (ie: only trimmed top/bottom), rather than downsampled from a higher resolution. I was able to squeeze better perf out of Cyberpunk 2077 in this way (and incidentally the DLSS had less smearing for some reason).

 

[XoR_]

What you describe is just increasing FOV. You can test it by making screenshot in ultra-wide at default FOV and then making screenshots in 16:9 with FOV where you see about the same things on sides of the screen and comparing/overlaying ultra-wide screenshot on top of 16:9 image. Some games like Quake 1/2/3 allow you to set FOV to even 179 degrees so you can use these for test if you have three ultra-wide monitors in eyefinity

In the past when I used 4:3 monitors I often set FOV too high - more like it is at 16:9. This gives the same result in the middle as if I use 16:9 resolution but also there is this vertical area... and it looks totally broken with weird way things render in especially corners of the screen.
It is because of this strange way image looks when you increase FOV without adjusting aspect ratio why it is not recommended to just increase aspect ratio without making screen wider.

BTW. This effect happens because we use 3 point perspective to render games.

If we had more correct and comparable to how we actually see in reality 5 point perspective and out of resulting "perception sphere" cut down rectangle to display the image would maybe look strange but would also make much more sense. The 3 point perspective works as an approximation - central area of image drawn using 5 point perspective is very similar to 3 point perspective - the closer to the center the less error there is.

Still of course even if we rendered 3d graphics correctly we would still be compelled to use the same exact FOV setting and it being dependent on aspect ratio. The resulting distortion on top and bottom of the screen if you used wider FOV for 16:9 screen would just make more sense visually.

Of course we don't do 5 point perspective to save on computational resources needed to draw 3D graphics.
Back when 3D was new it was hard enough to pull off 3 point perspective and then 3D acceleration hardware was solely optimized to handle it.
You could however design your game engine to pull off 5 point perspective.
I guess such things like correct perspective will be more popular once we move to path-tracing as with ray tracing using different cameras is fairly easy and comes for pretty much no additional computational costs.

p.s. Bonus fact - VR headsets really need 5 point perspective and use trick to correct normal 3 point perspective image . There are some small errors and distortions because it isn't native rendering using 5 point perspective and just hack. If you displayed 3 point render directly in VR without this correction I guess that bad things might happen These errors are worse if headset FOV is very wide - the wider the more it is important to draw image correctly versus just use cheap tricks to correct image drawn using 3d point perspective.


EDIT://
We use 3 point perspective because it is good enough approximation for the purpose of conveying illusion of 3d world.

In theory to make 5 point perspective all we need to do is to calculate locations of polygons differently. In practice bigger triangle if drawn as it is drawn currently by GPUs would show perspective error. To avoid it just don't use bigger triangles and/or tesselate them e.g. based on distance and/or position on screen. Yeah but that adds lots of complexity and the whole 5 point perspective would be much computationally expensive even without such tircks. And this doesn't even include shaders which these days can get quite complex and render 3D by itself.

Of course for 3D games all we need is approximations and not perfection - small errors here and there would still be better than everything having perspective error.

That is until you realize that correct as it would be we got quite used for straight lines to always be straight and not bent at sides. In fact more correct perspective might even be jarring. At least I would expect some people being like ecstatic, most wouldn't care and some would be bothered by bent lines.

I anticipate I would be like claiming its the biggest revolution in 3D gaming since moving from 2 point perspective of Doom to 3 point perspective of Quake.
Maybe if Carmack was still at Id and Id was independent we would see Quake 5 with 5 point perspective and then source code released shortly after