KSP has unrealistic/distorted 3D rendering

[cantab]

Playing around with the field of view option in KSP, which is Alt/RShift/Command and scroll wheel, I observe that KSP shows pure perspective distortion, and no barrel distortion. That means that straight lines, such as the edge of the VAB, remain straight but that right-angles no longer appear as right angles. Real camera lenses often exhibit barrel distortion, and all fish-eye lenses do, which would make the straight edges of the VAB appear to curve.

It is impossible to give a distortion-free image unless the angular size of the image as viewed matches the angular size as it was taken. This is easiest explained in pictures:

 

So a "wide angle" view in KSP has to be distorted. There's no way around that, it's the laws of physics. (Specifically, geometric optics.) Now the current approach, of KSP producing only perspective distortion, has the major advantage that it means that if you match the in-game field of view to your own view of the screen, the distortion will be nulled out. You could be sitting relatively close to a huge screen and the view would look correct. If KSP were, as an artistic choice, to introduce barrel distortion (a "fisheye" effect) to its view at wide angles, then you would never be able to get an undistorted view over such a wide angle whatever the size and position of your display.

https://en.wikipedia.org/wiki/Distortion_(optics)

https://en.wikipedia.org/wiki/Perspective_distortion_(photography)

 

[AlamoVampire]

@thereaverofdarkness2 with regards to your opening post of this thread, your pictures look to be fisheye lenses which heavily distort things, which has been covered by folks posting ahead of me. But, I like to restate the obvious. As far as things looking "very very wrong" in game as far as 3d modeling goes, I really do not see what you are seeing. To me, when I have a kerbal on the ground in EVA at the KSC things look as I would expect them to in real life as far as curvature of the horizon goes or how the horizon line is off in the distance. I think things look fine the way they are, after all kerbals are tiny little guys and the game is from their perspective so to speak. Just my thoughts of course. Results will inevitably vary.

[thereaverofdarkness2]

1 hour ago, AlamoVampire said:

@thereaverofdarkness2 with regards to your opening post of this thread, your pictures look to be fisheye lenses which heavily distort things, [snip] To me, when I have a kerbal on the ground in EVA at the KSC things look as I would expect them to in real life

What you're referring to as a "fisheye" lens is a wide angle view, and there is no way to avoid what you call distortion. Every flat rendition of a 3D image is distorted and the "fisheye" wide angle lens is a close representation of what we actually see when looking around. Our brains interpret this flat image differently from how they interpret the distortion we see in our peripheral vision.

You may feel like the scenery in KSP matches real life, but it does not, and this is easily seen by trying to compare it with real life. If you try to compare it by memory, it seems right (to you guys, apparently). But make a direct comparison and you will see that it is way off.

4 hours ago, klgraham1013 said:

So ever video game has unrealistic/distorted 3D rendering?  I must not be understanding something.

There's no way to truly match the screen graphics to what we see with our eyes, but I've never seen any other 3D game with the rendering style used in KSP. Perhaps it is this lack of barrel distortion as cantab said it. Our brains gloss over barrel distortion in our periphery, so at first it may seem right to eliminate it from the game. But putting barrel distortion into the game produces a more accurate image, it matches what real-world cameras will show, and you can get used to it over time. Most importantly, virtually every true 3D rendering game ever has some sort of barrel distortion...I'll name a handful of examples: Minecraft, EVE: Online, the Quake series, everything built with the Unreal engine, Half Life 1/2 and Portal 1/2, the list goes on and on and on. But examples of games without this distortion are rare and seem to be relegated to false 3D renders such as Wolfenstein 3D, the original Doom, or Duke Nukem 3D. KSP is the only true 3D game I can think of that renders this way.

[MalfunctionM1Ke]

The Thread Title should be "CHEAP CAMERAS HAVE UNREALISTIC LENSING EFFECTS"

Dont confuse curvature of the earth with Fish-eye lensing effects.

Actually it is pretty hard nowadays to find a camera that doesnt give recordings a fisheye-effect.
What I mean by this are effects like this:

It has nothing to do with what the horizon actually looks like but it extorts everything that is too far off the center of the picture.

Edited June 26, 2016 by MalfunctionM1Ke

[thereaverofdarkness2]

It has to do with the view angle. The edge is always distorted relative to the center, it's just that with a low enough view angle you can't see it anymore.

KSP rendering is not escaping this problem--because that's impossible--rather it is circumventing it in a way that drives me up the wall and apparently most people feel just fine with.

Edited June 26, 2016 by thereaverofdarkness2

[MalfunctionM1Ke]

7 minutes ago, thereaverofdarkness2 said:

The edge is always distorted relative to the center, it's just that with a low enough view angle you can't see it anymore.

No it is not.

Does the horizon bend when you look down in the top of your field of view? I would give the human eye ~120-160° of view.

[thereaverofdarkness2]

1 minute ago, MalfunctionM1Ke said:

Does the horizon bend when you look down in the top of your field of view? I would give the human eye ~120-160° of view.

Yes, it does. As I explained more than once already, our brains pretend it doesn't happen. Don't just assume it didn't happen because you didn't notice it. If you actually watch your peripheral view, you can see the "distortion".

But it happens less in our eyes because our retina is curved, unlike our flat computer screens. The only way to present a wide field view with no apparent distortion is on a dome over the player's head.

[MalfunctionM1Ke]

6 minutes ago, thereaverofdarkness2 said:

Yes, it does. As I explained more than once already, our brains pretend it doesn't happen. Don't just assume it didn't happen because you didn't notice it. If you actually watch your peripheral view, you can see the "distortion".

But it happens less in our eyes because our retina is curved, unlike our flat computer screens. The only way to present a wide field view with no apparent distortion is on a dome over the player's head.

Okay, that makes sense. But I dont think a fisheyed-view would be very realistic for KSP.

[pandaman]

As I said earlier in the thread, I noticed that the image is distorted towards the edges, and yes, it looks a bit odd, particularly when planets don't look spherical, but I don't have a big issue with it,   It would 'look nicer' IMO if it didnt do it, but that's all.  I first spotted it on screen shots and thought it was possibly distortion caused by that process somehow, but then noticed it in game too. 

I understand that it's down to how the game 'view camera' works,  and for the most part I don't notice it much, depending on the scene.

Edited June 26, 2016 by pandaman

[The Aziz]

Seriously, I 'd like to see what my brain tries to tell me what I see, rather than artificial picture made by camera lens. 

 

There goes whole "earth is flat" society. 

Also, some of these pics..

12 hours ago, thereaverofdarkness2 said:

 

Earth is few kilometers in radius.

12 hours ago, thereaverofdarkness2 said:

 

Earth is a donut.

 

Also, I tried. At 1920x1080 shot, FOV not tweaked, not much more that two meters ASL, there is two pixels difference between center of image and edges. Ocean, of course.

About 200 meters higher it's 10 pixels.

Edited June 26, 2016 by The Aziz

[Majorjim!]

Except this has an unwanted effect on things. Zoom in on a Kerbal in 1.1.3 and you will see it cut off the render far too early, taking slices out of the picture. This ruins a lot of possible shots for cinematics in KSP.

[moogoob]

10 hours ago, thereaverofdarkness2 said:

 Most importantly, virtually every true 3D rendering game ever has some sort of barrel distortion...I'll name a handful of examples: Minecraft, EVE: Online, the Quake series, everything built with the Unreal engine, Half Life 1/2 and Portal 1/2, the list goes on and on and on. But examples of games without this distortion are rare and seem to be relegated to false 3D renders such as Wolfenstein 3D, the original Doom, or Duke Nukem 3D. KSP is the only true 3D game I can think of that renders this way.

I... no they don't. No game has this, especially not Minecraft or Quake. They distort the exact same way as KSP. Only games developed for VR - Oculus, Vive, etc have it in order to project into the fisheye lenses that project into the eyes. You must be talking about something else.

EDIT: The default projection is basically (glossing over a lot of details) what those of us that have taken high school art class know as "3-point perspective drawings". They let you draw a 3d space using nothing but flat lines - perfect for a computer to try and tackle in real time! Guess what - a 3-pt persp. drawing has the same distortion effects when you get the the edges of a drawing as 3d rendering has at the edges of an image.  Curved lines are very, very computationally intense, so are avoided unless absolutely needed - IE, projecting into a head-mounted display.

Edited June 26, 2016 by moogoob

[Tw1]

10 hours ago, thereaverofdarkness2 said:

 The only way to present a wide field view with no apparent distortion is on a dome over the player's head.

I've been in a dome theatre! So cool, one at my university, and one in the USA somewhere. near grand canyon maybe? 

But yeah. Those photos are not consistent with that world outside I look at pretty often. So...

[thereaverofdarkness2]

10 hours ago, MalfunctionM1Ke said:

Okay, that makes sense. But I dont think a fisheyed-view would be very realistic for KSP.

It wouldn't look fish-eyed at a normal view angle. I was showing an extreme to point out the difference. Please read the post before you try to discredit it, people!

1 hour ago, moogoob said:

I... no they don't. No game has this, especially not Minecraft or Quake. They distort the exact same way as KSP.

Not even close, and if you turn up the view angle (something you can do in the settings in Minecraft and Quake), you will see something completely different from when the view angle is turned up in KSP.

But don't take my word for it. I want you to go try it yourself so you can really see what I mean. When you turn up the view angle in KSP, nothing seems to change. Maybe this makes it look "correct" to the untrained eye, but it also more or less eliminates the potential benefit of having the view angle increased in the first place. Why even have the option to do it? It doesn't really work in KSP.

4 hours ago, Majorjim said:

Except this has an unwanted effect on things. Zoom in on a Kerbal in 1.1.3 and you will see it cut off the render far too early, taking slices out of the picture. This ruins a lot of possible shots for cinematics in KSP.

This is one of many unwanted effects from the way KSP renders, and these bugs only happen in KSP.

Edited June 26, 2016 by thereaverofdarkness2

[moogoob]

18 minutes ago, thereaverofdarkness2 said:

Not even close, and if you turn up the view angle (something you can do in the settings in Minecraft and Quake), you will see something completely different from when the view angle is turned up in KSP.

But don't take my word for it. I want you to go try it yourself so you can really see what I mean. When you turn up the view angle in KSP, nothing seems to change. Maybe this makes it look "correct" to the untrained eye, but it also more or less eliminates the potential benefit of having the view angle increased in the first place. Why even have the option to do it? It doesn't really work in KSP.

Those games don't have barrel distortion, period, so that's clearly not what you are talking about. Are you talking about them having a particular field-of-view and that the default FoV in KSP is different or handled differently?

Either way, horizontal lines will still not curve when at the edges of the view area. Can you take a screenshot of one of those games you mentioned that demonstrates your point? Cause right now I'm a bit confused as to what it is, exactly.

[thereaverofdarkness2]

12 minutes ago, moogoob said:

Those games don't have barrel distortion, period, so that's clearly not what you are talking about.

I don't actually know what barrel distortion is, it just sounded like it might be what I was referring to.

12 minutes ago, moogoob said:

Are you talking about them having a particular field-of-view and that the default FoV in KSP is different or handled differently?

Either way, horizontal lines will still not curve when at the edges of the view area. Can you take a screenshot of one of those games you mentioned that demonstrates your point? Cause right now I'm a bit confused as to what it is, exactly.

They have what I like to call "British Flag" distortion. It seems to stretch outward at the diagonals and pull inward (or just stretch less outward) at the orthogonals. This rendering style keeps everything in straight lines, as you explained above. KSP does not do this. I don't know what it is doing, but I know it's doing it differently. KSP has straight lines, too, but with a different rendering method.

Edited June 26, 2016 by thereaverofdarkness2

[rkman]

17 minutes ago, thereaverofdarkness2 said:

I don't actually know what barrel distortion is, it just sounded like it might be what I was referring to.

 

They have what I like to call "British Flag" distortion. It seems to stretch outward at the diagonals and pull inward (or just stretch less outward) at the orthogonals. This rendering style keeps everything in straight lines, as you explained above.

KSP does not do this.

Yes it does:

straight lines remain straight, and everything stretched out toward the edges of the screen

Edited June 26, 2016 by rkman

[OHara]

^That [ed: the thereavdark post] is a large angular field-of-view.   Straight lines remain straight, so usually in optics we would call that zero rectilinear distortion.

Try alt-+ with the number keypad +, or (left)alt with whatever you would use to zoom, to see larger angular field-of-view in KSP

Edited June 26, 2016 by OHara

[thereaverofdarkness2]

1 minute ago, OHara said:

Try alt-+ with the number keypad +, or (left)alt with whatever you would use to zoom, to see larger angular field-of-view in KSP

I already did that. That's how this post got started.

3 minutes ago, rkman said:

Yes it does:

I'm starting to think you might be right. When I compare KSP to Minecraft, they do seem to render the same way.

Why, then, did it never bother me in other games? Maybe it's because they don't send you off into space, or because they have a horizon that's actually flat.

[thereaverofdarkness2]

But KSP really does look strikingly different from Minecraft or Quake at high FoV angle. I can turn KSP's view angle up to 120º and without studying the edge of the screen while rotating the camera, I can't even tell that the FoV is turned up. But in Minecraft the distortion is readily apparent even at 90º. And there is a huge difference between 90º and 120º. I turned it up to the max in KSP which by my rough estimation is somewhere near 150º and it looks about as distorted as Minecraft at "Quake Pro" 110º. More importantly, it doesn't produce the "British Flag" effect as I turn the camera. It has a different effect, something I'll call the "Space Odyssey" effect. It's like this image, but if you turn it on it's side:

As best as I can describe it, it seems to be distorting to a flat horizon, almost as if the game were drawn onto two flat plates and we were standing between the plates, with one above us and one beneath us, and we're looking off into their vanishing point. Minecraft doesn't do this and Quake doesn't do this. But then Quake doesn't quite do the "British Flag" distortion either, but it looks much more like Minecraft and much less like KSP.

[Fred Cop]

*Never mind, someone already mentioned 'Alt + Scrollwheel'*

Edited June 26, 2016 by Fred Cop

[Merandix]

I'm not 100% sure if I'm right, because I'm certainly no expert on the human eye, but a bit of logic and a few articles make me think this topic confuses how camera optics work and how the optics of the human eye works.

The human eye actually isn't anything like a camera, apart from the basic principles.

IF you compare the two in the strictest sense, the human eye has a focal length equivalent of about 43mm on a full-frame sensor (but many focal lengths between 35 and 50 mm are usually given). Which actually isn't wide angle at all, but from what I've always understood is more like the middle-ground. Which makes sense, wide-angle and high zoom both produce significant distortions. If you think about this, it's actually quite logical why we don't see distortions, it's not our brains, but it's the fact that the photosensitive receptors on the back-side of our eye are actually not situated on a small flat plane like on a camera chip, but they are situated on the inside of a spheroid. A spheroid which very likely has (near) the same curvature as the lens-distortion.

Why we get such a wide angle view anyway? The ENTIRE (almost the entire) back of our eye is literally plastered with photosensitive receptors, also outside our focal view. Which means that even if we directly compare the optics of a camera with the optics of our eye, the human eye will give a far wider angle, because the human eye simply works differently than a camera sensor. In the human eye, the 'sensor' sort of 'wraps around' the lens.

Lens distortion is actually the technological shortcoming of the fact that a curved lens cannot deliver a perfectly undistorted image on a  (fairly small) flat surface. It's also technological greed, because this shortcoming (tiny sensor) also means we can change focal length on the fly (zooming).

I think it comes down to taste. Point is, our peripheral vision works differently than a camera producing a wide angle shot. In fact, the camera is struggling to deliver all that light to the positively tiny flat chip. Our eye doesn't have to put all light that enters on such a small area. And in fact, we don't have a uniform resolution density in our eye. Our peripheral vision has lower resolution than the centre of our vision.

You basically have to picture KSP's vision like an eyeball floating behind the Kerbals, and we get to see a small cutout from what that eyeball sees. However, it is an eyeball with uniform resolution, because otherwise, we'd use too little of our screen real estate. Another reason is that the screen (in most home setups) only covers a small portion of our vision. Producing too much distortions (which simulate peripheral vision) actually makes games more prone to people getting 'game sickness' (of which quake and Minecraft are examplles often named by people experiencing game-sickness, which is a variant of motion sickness).

Basically, it comes down to taste, but there's nothing 'unrealisitc' about it, it's just questioning whether to fully simulate all optics in a fairly narrow field of view (talking about the monitor, not fov on screen), or not. Especially combined with the fact that not all eyes are equal.

[klgraham1013]

12 hours ago, thereaverofdarkness2 said:

Yes, it does. As I explained more than once already, our brains pretend it doesn't happen.

I'll take the view our brain creates over the view our eyes do.

 I'd rather not have a fish-eyed, upside-down,  image with a blind spot.

[thereaverofdarkness2]

5 minutes ago, Merandix said:

the human eye has a focal length equivalent of about 43mm on a full-frame sensor (but many focal lengths between 35 and 50 mm are usually given).

Focal length isn't a measure of field of view. Our eyes have a field of view close to 180º which is utterly immense for any camera. You can't do it with just a lens, you have to curve the CCD plate to get that effect AFAIK. Comparing the focal length of our eyes to that of a handheld camera is useless without other data because they have a different lens size.

[HazelPine]

I'll just leave this here:

Looks like it works to me...