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Why The Fuck Does Perspective Distortion Happen In 3D Graphics?

Anonymous Sat 19 Dec 21:02:16 2020 No.12485097 View Reply Original Report

Quoted By: >>12485109 >>12485116 >>12485195 >>12485257 >>12490548 >>12490567 >>12491391 >>12491401 >>12491434

I don't fucking get it. I cannot wrap my head around this bullshit and it's pissing me off. None of the "explanations" online give any explanation at all, they all just repeat the same "high field of view distorts the image" - I fucking get that, I want to know WHY.

WHY the fuck can't 3D graphics be rendered without perspective distortion? Why the fuck are objects at the edge of the FOV zoomed in while things in the middle aren't? Why the fuck can't that be corrected while rendering? It's not a real system, it's not a real lens, physical imperfections don't apply and the rules don't matter, so why the god damn fuck does perspective distortion happen?

Anonymous

Anonymous Sat 19 Dec 2020 21:04:08 No.12485109 Report

Quoted By:

>>12485097
I dont know either but now i really want to know

Anonymous

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Anonymous Sat 19 Dec 2020 21:05:38 No.12485116 Report

Quoted By: >>12485129 >>12485257 >>12485588 >>12487548

>>12485097
Here's an even more obvious example from Minecraft, which is a great model for what I'm talking about because everything is made up of cubes.

Why the fuck are the pillars on the sides stretched to hell and back, while the ones in the middle look fucking fine? If I were standing in front of 4 pillars exactly like this, they would fucking looking straight and the correct size throughout my entire field of vision. Why the FUCK do they not do that in a fucking game where the 3D rendering engine can be literally anything you want because physics don't apply in a god damn computer program? WHY?

Anonymous

Anonymous Sat 19 Dec 2020 21:08:10 No.12485129 Report

Quoted By: >>12485134

>>12485116
Physics doesn’t, geometry does

Anonymous

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Anonymous Sat 19 Dec 2020 21:09:26 No.12485134 Report

Quoted By: >>12485150 >>12485176 >>12485575 >>12490098 >>12490550 >>12490796

>>12485129
WHAT ABOUT GEOMETRY MAKES IT NOT WORK

WHY DO MY FUCKING EYES WORK AND THIS SHIT DOESN'T

Anonymous

Anonymous Sat 19 Dec 2020 21:11:29 No.12485150 Report

Quoted By:

>>12485134
pathetic brainlet btfo by geometry, the most basic kind of math

Anonymous

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Anonymous Sat 19 Dec 2020 21:14:45 No.12485163 Report

Quoted By:

geometry absolutely mogging this poor anon

i dont have an answer either btw

Anonymous

Anonymous Sat 19 Dec 2020 21:17:48 No.12485176 Report

Quoted By:

>>12485134
>WHY DO MY FUCKING EYES WORK AND THIS SHIT DOESN'T
It's because large fields of vision distort the image at the edges. You'd know this if you googled it even once.

Anonymous

Anonymous Sat 19 Dec 2020 21:22:25 No.12485195 Report

Quoted By: >>12491404

>>12485097
Because you're projecting a 3D sphere onto a plane. The same reason why world maps look distorted as well. You could project it in a way that is distorted differently, but it will always be distorted in some way.

Anonymous

Anonymous Sat 19 Dec 2020 21:32:01 No.12485257 Report

Quoted By:

>>12485116
The essence of the problem here is that you want to see a wider piece of the world than can really fit on a 16:9 screen.

Human eyes can see much more horizontal width than vertical height. Partly because of the structure of your eyes, and partly because your eyes are horizontally next to each other but vertically on the same level, your field of view is maybe four times as wide as it is tall. This ratio is much greater than the 16:9 ratio of a typical monitor.

This means that a game played on a 16:9 monitor has to choose between two shitty options. It can accurately show a true 16:9 viewport, but then you will have terrible tunnel vision, and you will not be able to see many things that a human could easily see from the corner of his eyes in real life, because they would fall off the side of the screen.

Or you could squish the graphics horizontally a bit, so that you can see more of what's around you, at the cost of distorting the image, particularly noticeable in perspective things. That's what the high-FOV setting does, and what's going on in >>12485116. There is a careful tradeoff here between how much distortion is acceptable, versus how much tunnel vision you are willing to tolerate. Of course, the real solution is to get an ultrawide monitor.

>>12485097
This, on the other hand, is super fucked and has nothing to do with field of view or perspective. No clue what's going on there, though the filename gives some hints.

Anonymous

Anonymous Sat 19 Dec 2020 22:48:20 No.12485575 Report

Quoted By:

>>12485134
to get it perfect you'd need to measure the angle between your eye and the sides of your screen to know what FOV to set it to

Anonymous

Anonymous Sat 19 Dec 2020 22:51:00 No.12485588 Report

Quoted By:

>>12485116
>Why are the pillars on the sides stretched to hell and back, while the ones in the middle look fucking fine?
It's because the image is projected onto a plane. Any planar image will appear distorted when viewed from the incorrect angle, or from too close or far away.
This is a very wide-angle view so the edges appear stretched.
In theory, if your eye were the proper distance from the plane, there would be no apparent distortion.

Anonymous

Anonymous Sun 20 Dec 2020 12:38:45 No.12487548 Report

Quoted By:

>>12485116
Since those shapes are consistent I'm pretty sure you could calculate the exact distance your eye needs to be from the image for the perspective to look right.

Anonymous

Anonymous Mon 21 Dec 2020 01:59:13 No.12490098 Report

Quoted By:

>>12485134
Irl your eyes have a horizontal fov of around 200 degrees. The screen only takes up about 20 degrees of vision depending on size of and distance to the screen, but games run at around 90 degrees fov. So it is literally stretching 90 degrees of fov into 20 degrees which is why it appears stretched.

Anonymous

Anonymous Mon 21 Dec 2020 05:02:31 No.12490548 Report

Quoted By: >>12491391

>>12485097
Because you're too far away from the screen. If you were projecting it onto a gigantic cinemascope screen so that the edges were way off to the side, it would look perfect.

Anonymous

Anonymous Mon 21 Dec 2020 05:03:22 No.12490550 Report

Quoted By:

>>12485134
>WHY DO MY FUCKING EYES WORK
Because your eyes have a spherical retina, matching the lens, whereas the computer graphics are "projected" onto a virtual flat plane.

Anonymous

Anonymous Mon 21 Dec 2020 05:08:54 No.12490567 Report

Quoted By:

>>12485097
coz it's not a Euclidean plane.

Anonymous

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Anonymous Mon 21 Dec 2020 06:42:09 No.12490796 Report

Quoted By: >>12491391

>>12485134
maybe it is because your eyes have a curved retina but cameras(real or virtual) have flat 2D surface that records the picture.

So your eyes don't 'see' the effect because it is cancelled out by the shape of the retina.

You might need to code a virtual camera that takes this into account.

Anonymous

Anonymous Mon 21 Dec 2020 11:32:01 No.12491391 Report

Quoted By: >>12491420 >>12491423

>>12490548
In the case of OP's image, which has a projection angle that's looks like it's about 180 degrees wide, or 90 degrees from center, putting an eye about 5" from a 50" monitor almost does the trick.
>>12485097
And though no one sits 5' away from a 50' theater screen, it is always possible to adjust the projection parameters in 3D CGI to perfectly map to a 2D screen surface if the angle is a match to viewing arrangements--which at a desktop is usually about a 20 to 30 degree sweep from one edge of the screen to the other from the viewer's perspective, as high as 90 if you're being a bit silly with screen sizes and distances from them. For instance I use oversize monitors to allow comfy reclining in long sessions, but go to ridiculous projection angles once in a while to render something that looks right when sitting up and leaning into one of them for extra sensations of yesteryear's immersive fun at Omnimax theaters. Of course designing camera optics that are free of both noticeable geometric distortion and chromatic aberation at wide fields-of-view is a whole lot more difficult and complicated than CGI projection is, but in neither case does it directly pertain to the geometry of the eye in the way that this >>12490796 possible troll suggests.

Anonymous

Anonymous Mon 21 Dec 2020 11:38:31 No.12491401 Report

Quoted By:

>>12485097
almost anything being projected from 3D to 2D will have loss. if you don't believe me, try it, and if you find out a way, you might win a Nobel Prize

Virtual Reality headsets don't suffer as much from this problem because they're not projecting into 2D space.

It's the whole example where you try to cut an orange peel and make it flat to learn about map projections.

Anonymous

Anonymous Mon 21 Dec 2020 11:40:46 No.12491404 Report

Quoted By:

>>12485195
this is the simplest answer

Anonymous

Anonymous Mon 21 Dec 2020 11:48:25 No.12491420 Report

Quoted By:

>>12491391
>about 5" from a 50" monitor almost does the trick.
You're not kidding, it really does. Just tried it.

Anonymous

Anonymous Mon 21 Dec 2020 11:50:01 No.12491423 Report

Quoted By:

>>12491391
Yeah exactly. From a normal position, the actual field of view from one edge of your screen to the other is probably about 45 degrees, so any more than that in-game will look distorted.

Anonymous

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Anonymous Mon 21 Dec 2020 11:54:00 No.12491434 Report

Quoted By:

>>12485097
>WHY the fuck can't 3D graphics be rendered without perspective distortion?
Anom what are you mean by this?

Anonymous

Anonymous Mon 21 Dec 2020 12:00:40 No.12491444 Report

Quoted By:

Field of view. The "square" thing you look through, the monitor, does not really provide you with the ability to see much. Without the distortion effect you will look through a pinhole.
Older games, from the era before you were born, offered hacks and other illegal modifications that luckily are widely banned today such as hitting the ~ key and typing
>fov 60

Real men played at around 110 before things got wonky.

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