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Comment by p1necone | Hacker News Reader

This runs pretty smoothly on my middling laptop CPU while looking like a typical raytracing demo. I assume there's some smoke and mirrors involved?

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No, it's using the newish SSGI and TRAA webgpu nodes. The three team has been making great progress with SSGI and webgpu in general and i'd recommend checking it out if you're interested.

There's also a denoise node in three (not used in this example), but SSGI still looks kinda blurry.

Work though is still going on: https://github.com/mrdoob/three.js/issues/31892

Jesus Christ, trying to figure out what TRAA is (presumably an anti-aliasing algorithm) and how it works and it's entirely impossible to google.

Temporal reprojection anti aliasing :)

https://www.threejs-blocks.com/docs/traaHD

The only thing even remotely related to graphics I found was references to "TrAA" in forum posts from 2006 (yeah) where I believe they referred to NVIDIA "Transparency AA" or something like that. "TRAA", "TRAA meaning", "TRAA graphics", "TRAA 3D" all gave fully irrelevant results :D

If you make the assumption that "AA" is some form of antialiasing, it's not too bad: first scholar[1] hit expands the acronym to Temporal Reprojection Anti-Aliasing

    [1]: https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=traa+anti+aliasing&btnG=

Yeah, should've tried with "antialiasing". Still, astonishingly obscure given that it's not even a new thing anymore and apparently implemented in UE4 and others.

TRAA basically works by using a history buffer, for example using the last couple of frames, all jittered a little bit to compute the pixel. There's still ghosting and smearing that can happen though because of this technique, so you have methods to counteract like subpixel correction where u increase temporal alpha when velocity is subpixel, but that can introduce some artifacts as well.

There's also SMAA T2x which the pmndrs team is planning on integrating into their postprocessing package[0]. This cryengine3 slideshow gives a nice overview of antialiasing methods if you're interested: http://iryoku.com/aacourse/downloads/13-Anti-Aliasing-Method...

[0] https://github.com/pmndrs/postprocessing

This paper also provides a decent overview of TRAA: https://fileadmin.cs.lth.se/cs/Education/EDAN35/projects/17C...

The free Google AI mode got it for me on the first try by just pasting in the comment and asking what TRAA was in that context.

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