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Comment by skippyfish | Hacker News Reader

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.

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one, the article is 14 years old. two, the point of ambient occlusion was not about making geometry look good, it was about making lighting look good.

The main issue it solved was normal lighting at odds with the world, it was for fast general approximation of global illumination.

Another point of context: at the time, several popular games had used a very exaggerated and/or poorly implemented ambient occlusion feature. I personally would frequently turn it off entirely because it was generally expensive (even if not as expensive as full global illumination) and looked bad.

I think the prime example of SSAO being helpful was Fallout 3. FO3 has very simplistic lighting even for its time, kind of looking like "fullbright"/non-shaded mode in Source engine. SSAO, when it was added as a graphics driver feature, suddenly gave interiors depth that they were severely lacking, and while it didn't always look "realistic", it almost always looked much better than without.

When I look around me at my actual room it feels like if I saw it accurately depicted in a video game I'd call it lacking depth. The walls are flat colors, and there's barely anything delineating the wall from the ceiling - only a slight change in the light intensity. I know it's there and I have binocular vision, but by raw pixels, there isn't much to tell them apart. It may be that such things have to be exaggerated to get across through the medium of a game, like how cartoon characters always have to squish and stretch when they jump to make it obvious that they are jumping.

Crysis was the first, if you remember it. It changed FPS’ forever, introduced some new open world mechanics, as well as being the first game to utilize SSAO.

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