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Hacker News
As an artist, I was taught that when dark area meets a lighter one, I should add a slight gradient, deepening the dark near light.
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.
by lesostep
I find this very interesting. I have implemented AO myself and understood that its physically inaccurate (it should really be radiosity presence, not ambient occlusion), but have believed the results to look realistic. Or rather; better than flatly lit, which makes geometry hard to understand.
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!
by logdahl
SSAO is cheap, doesn't work that well and looks terrible if overdone, as many games did 10-15 years ago. The simple workaround is to dial down the SSAO so that it's maybe weaker than ambient occlusion in reality, but also not noticeably wrong or overdone. Fortunately, the settings often allow that. Problem mostly solved!
It's a common pattern that newly possible (usually due to hardware) effects are overdone for the wow / up-to-date look effect.
by ahartmetz
Discussed previously here in 2022: https://news.ycombinator.com/item?id=30595038
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.
by jameshart
SSAO really is awful but it’s the best performing AO we could get for a long time afaik. It’s such a hallmark of 00s and 10s rendering that I laugh every time I see it in a modern release. There are some new solutions hitting the space, I believe RTGI/PT inherently handles AO, and there is even a new method called ‘FidelityFX CACAO’ which does look considerably more realistic. Things are improving… slowly.
by mfro
> https://nothings.org/gamedev/ssao/IMG_0059.JPG
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 agree with his overall point, but I would point out: realism is not usually the point, the point is to look good. The problem with realism is once you get past "wow the computer can do that now", it's not very interesting -- most of reality is pretty dull looking!
by overgard
I don't think the author makes a persuasive argument. Most of the photos they're analyzing are obviously lit by various point light sources, e.g.:
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.
by skippyfish
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- Hacker News
- As an artist, I was taught that when dark area meets a lighter one, I should add a slight gradient, deepening the dark near light.
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.
by lesostep - I find this very interesting. I have implemented AO myself and understood that its physically inaccurate (it should really be radiosity presence, not ambient occlusion), but have believed the results to look realistic. Or rather; better than flatly lit, which makes geometry hard to understand.
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!
by logdahl - SSAO is cheap, doesn't work that well and looks terrible if overdone, as many games did 10-15 years ago. The simple workaround is to dial down the SSAO so that it's maybe weaker than ambient occlusion in reality, but also not noticeably wrong or overdone. Fortunately, the settings often allow that. Problem mostly solved!
It's a common pattern that newly possible (usually due to hardware) effects are overdone for the wow / up-to-date look effect.
by ahartmetz - Discussed previously here in 2022: https://news.ycombinator.com/item?id=30595038
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.
by jameshart - SSAO really is awful but it’s the best performing AO we could get for a long time afaik. It’s such a hallmark of 00s and 10s rendering that I laugh every time I see it in a modern release. There are some new solutions hitting the space, I believe RTGI/PT inherently handles AO, and there is even a new method called ‘FidelityFX CACAO’ which does look considerably more realistic. Things are improving… slowly.by mfro
- > https://nothings.org/gamedev/ssao/IMG_0059.JPG
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 agree with his overall point, but I would point out: realism is not usually the point, the point is to look good. The problem with realism is once you get past "wow the computer can do that now", it's not very interesting -- most of reality is pretty dull looking!by overgard
- I don't think the author makes a persuasive argument. Most of the photos they're analyzing are obviously lit by various point light sources, e.g.:
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.
by skippyfish