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Corners Don't Look Like That: Regarding Screenspace Ambient Occlusion (2012)
(nothings.org)
188
91
by firephox
by firephox
https://nothings.org/gamedev/ssao/IMG_0064.JPG
You can see a sharp shadow near the door frame. So yeah, ambient occlusion is not going to simulate that, but it was never supposed to?
It's supposed to make 3D shapes look good without the need to place lights or do more complex ray tracing. It roughly approximates what you could perhaps see inside a photographic lightbox. Light is coming from every direction and every surface is matte.
The reason it's used in computer games is not that it's photorealistic under all lighting conditions. It's that it makes geometries look better than before with less computational overhead than the alternatives. Harsh lights often look nasty and diffuse lighting is expensive.
The main issue it solved was normal lighting at odds with the world, it was for fast general approximation of global illumination.
i wonder if this is on purpose to avoid this illusion where i cant tell if im looking at a convex or concave just from three lines
I still can’t help but read most of this article as a story of a guy trying to prove his theory that corners aren’t actually dark, taking photos and plotting luminance graphs of corners, repeatedly getting these strong vee-shaped graphs that indicate that the surface darkens linearly towards the corner, and just gathering more and more pictures until eventually he finds some which show flat luminance lines, at which point he declares victory because he’s proven that corners don’t darken.
It's a common pattern that newly possible (usually due to hardware) effects are overdone for the wow / up-to-date look effect.
Examples?
Thank you for these photographs! It would be awesome to have a CG benchmark like this (geometry + light properties) that we could compare to. I'm sure this exists already but. Very neat!
Is it realistic?
No. But it looks more realistic. Because as our eyes track across real room, they adjust to the brightness.
So the darker region would look much darker near a light region – not on camera, but to human eye. And we replicate that effect in drawing, to trick the nerve behind the eye into believing that our pupil adjusted.
That's it, I think. We are not cameras, and our realism doesn't look like a photo.
Given that accuracy isn’t the goal anyway I’ve often wondered if it wouldn’t be better in many cases to apply a sort of pre-calculated AO that uses a relatively small atlas of shading textures rendered on flat surfaces as decals (disclaimer: I am not a graphics programmer). It’d apply only to angular surfaces (so for example human faces wouldn’t be included) but I’d say that 80-90% of the benefit of AO lies in things like corners of rooms anyway — it’s really just manmade objects that look bad without AO, organic shapes don’t suffer nearly as badly.
Many time in my traditional media classes I will use the term ambient occlusion (AO) and describe it in exactly the same way as I would to my 3D class. Specifically, I ask them to imagine being surrounded by a sphere of even light. In such a case, where would the shadows be? I follow this by discussing contact shadow (e.g. the dark line between your hands as they are placed together) and core shadow (e.g. the darkness of your nostrils). In 3D rendering, both these classes of shadows are served by the AO pass.
Certainly, I would say that AO is a natural phenomenon, but it is also an effect that can be used to sweeten the naturally flat effect of a raster engine like Eevee.
Also, looking just at inner corners of the room is too specific, SSAO affects creases everywhere, not just at the inner corners of the box.
Literally nothing real looks like CG. Shadows and lighting don't look like that. Optical effects don't look like that. People don't move like they do in games and CG animations. Physics IRL doesn't work like it does in games. Real world doesn't look like filtered JPEGs stretched over wireframes with LODs.
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I'm far from a neatfreak but if those are there can you imagine what the inside of bro's computer looks like? Poor thing is probably so hot
I'm reminded of a lecture I saw yesterday (on YouTube) by an artist with an optimistic view of AI. (I'm not about to talk about AI, it was the rest of the lecture that was more interesting.) He pointed out that the first movies were just recorded theater plays, but didn't attract big audiences because the experience of seeing the play in person was better - you had sound, depth perception, and maybe audience interaction. Only when cinematographers started exploiting the medium's own advantages did it really become a thing.
There was a first person who realized that you could literally cut and paste film together to put more than one location into the same film, there was a first person who realized that you don't need continuity in the real world to make continuity in a film. He used the example of a film that showed people climbing into a cannon, then cut to a different angle, then the cannon was fired, then cut to a shot of the moon getting bigger and bigger. In reality these were three completely separate filming arrangements, probably two different cannons, but when run together consecutively they tell the impossible story of people shooting themselves to the moon with a cannon. And you can't do that in a play. Nobody realised you could do that with cinema until someone did realise. By today's standards it is obvious you can do this, but it wasn't back then!
There was the same thing with the sound recorder. Initially people just taped bands playing and played it back as a substitute for a band. But then you eventually got bands that would play looping samples (literally tape pasted into loops) and use tape machines to speed up and slow down their sound and make weird effects you couldn't do live. And just what the heck is electronic music anyway?
The guy's point was that's going to happen with AI too, but that's not my point.
I think 3D rendering in games is at or slightly past the midpoint of the same cycle. At first the goal was to recreate reality on the screen. Humanity achieved that goal around the time of Crysis. And it's a fine state to be in - it does work well - but there is more that a computer do. Actual reality is better than perfectly simulated reality on a screen, just like a live play is better than a recording of one, so the point is to go beyond reality.
Games have traditionally not really cared about stylizing the graphics so much as stylizing the gameplay, but I can think of some games, like Antichamber, where the graphics are doing completely unrealistic things.
idk what my point is here but just do darkened corners if you think they look good in your game.
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Corners Don't Look Like That: Regarding Screenspace Ambient Occlusion (2012) - https://news.ycombinator.com/item?id=30595038 - March 2022 (43 comments)
Corners Don't Look Like That: Regarding Screenspace Ambient Occlusion (2012) - https://news.ycombinator.com/item?id=18559477 - Nov 2018 (36 comments)
Corners Don't Look Like That: Regarding Screenspace Ambient Occlusion (2012) - https://news.ycombinator.com/item?id=10105437 - Aug 2015 (19 comments)
It's common for games to have an intentional designed aesthetic which uses cultural and social and graphical "languages" to create specific emotional impacts and effects. The lower the budget the more this is leaned into for expedient reasons but that in turn creates genre expectations! Low-poly and 8-bit are fine examples of what were once a product of technical limitations becoming their own target.
Subject matters also, and the overall aesthetic of the game; triple-A games often push towards what you're describing, that the most impactful and compelling may also be the most real...
...or at least, contain elements of it. Lots of games mess with color shading and saturation etc for the impact-reasons...
I do look forward to the era of more "photorealistic" rendering as you prefer, especially for natural landscapes like those I enjoy IRL. Some of which can have very "unnatural" feeling swings in tone and all sorts of things! I was just up in the mountains this week and saw a lot more variation in lighting and its impact on a consistent landscape (mountains across a lake) than I've ever seen in a game engine so far :)
I would say the sky and a private eye's dimly lit, smoke-filled 1920s office are pretty different, actually.
Another problem with looking good is that it's a) subjective (since it has no real or objective reference point, really) and b) it quickly goes stale once something else looks "better". Just look at Doom. It looked good in 1993, everyone would agree on that. It's not realistic, never was realistic and will certainly never be realistic unless you take a particular cocktail of drugs, I guess.
This is extremely untrue. It may be true that you spend most of your time in a dull-looking office or apartment, but most of reality -- at least here on Earth -- is quite visually interesting, and games are usually placed in visually interesting environments rather than set entirely within an office or apartment.
Beyond that, I would argue that the entire point of realism is not looking good (although it can look good), but rather immersion. The intent is to transport you to another world and make you feel like you're actually inside the scene. If your goal isn't to do that, then there's no need to bother with realism at all, and you can instead opt for highly stylized graphics that are intentionally designed to maximize aesthetically pleasing appearance and gameplay readability.
As a player, I'd rather compromise realistic rendering in order to be able to see the contours of things.
I was excited when seeing things that are wonderfully realistic, but just as a sign of how far we have gone in computer graphics.
[1] https://www.scientificamerican.com/article/are-the-colors-in...
Now suppose some aliens arrived at our planet and said: "Wow, your planet is the most-boring we've ever seen, it's all just one N2-colored ball." We'd be a little offended! Clearly, the dumb aliens are looking at it wrong!
Flip that in reverse, and we have an artistic obligation to choose "good colors" for planets that maximizes their interesting features. We already did it for surface-views on Earth.
If there's an alien living outside of the superconductor it probably has eyes that can sense all four components of the electroweak force, including the combination that we call electromagnetism, which is the only one that can pass through the weak force superconductor. Such a being would see the superconductor "material" as something like a block of red jello, only allowing one "color" to pass through and would be as surprised to see us there as we would be if we saw sentient beings inside a block of YBCu superconductor alloy.
Although we wouldn't have a way to see sentient beings inside a block of superconductor alloy, because we don't have any more long-range forces to probe it with, besides gravity. Our outside-weak alien could still see us with electromagnetism which is the one remaining long-range force we have, but that's disabled inside an electric superconductor too.
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This is in contrast to the realism of "if you were there in person". If you step outside and look towards the sun and see lens-flares, consult an eye-doctor. If you see polyhedral lens-flares or bokeh... consult a roboticist.
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And yet somehow we can understand videos and photos just fine.
Videogames have to overcompensate when they're missing lots of other important cues, but the closer they get to realism the less they have to overcompensate.
This is, I think one of the biggest differences between a skilled and amateur photographer. Amateur photo and video work looks flat because they are pointing the camera at a scene that looks fine to them in reality, but the resulting 2D image is flat and they don't know why or what to do about it.
I find a particularly stark example is forests. Walk into a random forest and you will find your sense of being surrounded and in an immersive, evocative, deep space to be very strong. Then fire off a quick photo and the result will be a chaotic uninspiring flat mess.
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https://www.youtube.com/watch?v=vBZ7NEyPUDw
https://frictionalgames.com/2014-01-tech-feature-ssao-and-te...
https://www.uni-konstanz.de/mmsp/pubsys/publishedFiles/LuCoD...
https://www.gdcvault.com/play/1012326/The-Rendering-Tools-an...
Modern real-time ambient occlusion techniques can estimate the depth far more accurately and produce correspondingly more believable results, at the cost of performance.
https://www.researchgate.net/figure/Visual-comparison-of-dif...
I thought about doing several 3d normal scales at pixel offset - and then do a animated "hair" texture on those layers..
And before games this was true of movies and before that photos and paintings. A master cinematographer can spend hours lighting a shot that will later be praised for its 'gritty realism' :-).
I think a Horizon Zero Dawn developer characterized their approach as “more realistic than reality” or something along those lines, i.e. they were aiming for the kind of perfect saturated look that you would only get in that golden hour with ideal surroundings but that we all recognize as real and at the same time don’t find too dull to stare at for hours. And I think for daytime HZD did do that quite well.
Likewise, Ansel Adams is particularly famous for popularizing manipulation of exposure, both in-camera snd during development.
By extension, this means that it is highly desirable to have a renderer capable of reproducing the real world as a baseline for highly controllable aesthetic tweaks. When you look especially at VFX specific tools, they have - almost without exception - two layers of tools: the first creates a realistic simulation (e.g. water/fire/shattering...) and the second layer allows for tweaks to control the final look.
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The lens flare isn't telling you the sun literally makes polygonal shapes. It's telling you the sun is fucking bright and it's dazzling you, and it's doing that by reference to something we've seen in films shot with cameras.
You can achieve it other ways. HL2 Lost Coast - Valve's HDR tech demo - conveys the same basic fact by delaying the tonemap change. As you walk from the dark area to the bright area, the tonemap stays set for the dark area so your whole screen is washed out in white, until it gradually shifts to normal over about half a second. This is also how your pupils work, of course.
As a purely temporal change it was neat, but I recall being distinctly annoyed with Lost Coast over how that effect made things worse (less realistic) for scene elements not under the crosshair / gun / avatar's-nose. We naturally expect contrast (and focus, see DoF rant) to improve when we direct our auto-adjusting eyeballs towards the area. In other words, realism of moving between light-environments came at the expense of realism in glancing around the room.
The straightforward fix would be gaze-tracking hardware... but now that I think about it (and with 20 years of tech improvements) I can imagine a much more mad-science approach: Track a simulated visual memory for the avatar!
Imagine a game that tracked recent virtual saccades to build up a cache of data like gaussian splats. So if that player has already seen the black notebook on the black desk in the dark room, it shows up more easily even if they walk in and out of the bright outdoors.
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It's not just games. I just saw an episode of a TV show in which two people were sitting in a car, talking to each other.
Whichever one of them was speaking was in focus. The other one was dramatically blurred. This traded back and forth rapidly, because that's how conversations work. It was incredibly bizarre.
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Any course on landscape photography will teach that landscapes should (usually) have a foreground, middle ground, and background. It seems kind of too obvious and too restrictive at the same time. But most of the time when I take a landscape photo and feel dissatisfied, it either breaks this rule or has very bad lighting.
