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Comment by MillenialMan | Hacker News Reader

Those rivets probably aren't modelled, they'll be reconstructed from volume information in the texture. Which is still impressive and a great way of dealing with that type of geometric detail, but it has limitations, and the engine isn't processing actual models at that level of detail.

You can still do stuff like that in UE4. Have a look at what's possible with Quixel Mixer, you can create detail like that surprisingly quickly. I'd tentatively argue that modelling tools are the real MVP when it comes to increased geometric LOD in modern engines. They allow you to add that kind of detail quickly enough that it becomes economical to actually detail rivets.

Either way, it's very cool. The crowd simulation stuff is going to be useful, current tooling there absolutely sucks outside of a few very expensive dedicated products.

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If this UE5 demo is using Nanite, then it really may well just be modeled geometry.

Nanite really blurs the line between geometry and texture - in a sense it’s a shader that uses triangle mesh data as if it were a texture source.

This siggraph session will expand your mind: https://m.youtube.com/watch?v=eviSykqSUUw

I stand corrected! Thanks for the link, that's very cool.

Yes. Nanite is very clever. A mesh representation that can be shown at a huge range of levels of detail is what makes it go. Much of the work is moved to asset preprocessing. The actual rendering is simplified. There are about as many triangles being drawn as there are pixels, regardless of scene complexity. If a triangle is bigger than a pixel, it's time to zoom in to a higher LOD for that part of the mesh. If a triangle is much smaller than a pixel, a higher LOD can be used. This is a reduction from O(N) to O(1). So draw time is constant regardless of scene complexity.

Watch the SIGGRAPH video to get the feelings of: that's impossible - oh, I kind of see how that works - one pixel triangles? - how do they get that mesh representation set up right? - oh, graph theory - that data format has to be a pain to generate with all those constraints - they're rendering mostly in the CPU? - that's all that needs to be done at render time? - GPUs need to be redesigned to be a better match to this - how to stream this stuff? - that compression scheme is clever.

It's very cool. I bet Digital Foundry takes an in-depth look - can't wait.

After reading your comment I went back in to the demo to have another look at the rivets up close. In the options menu, you can switch the viewport so that it shows you the triangles that make up object geometry under the "Nanite" system. Would be interested to hear from anyone with access to the demo and the right background what they make of this.

Edit: I took a couple of screenshots of default view vs Nanite triangles view but not sure what the convention is on HN for where to host them. Happy to put them up if someone can clue me in.

Edit: I've just put the screenshots up [here](https://imgur.com/a/2FMpLJa) and a ~30 sec vid [here](https://youtu.be/s1PUCadh1TU), showing cycling through the viewport modes.

Host them where ever you like, but hopefully something resilient to a hug of death.

I hear tweet threads are really appreciated /s

Replying to myself to add: Digital Foundry [analysis](https://www.eurogamer.net/articles/digitalfoundry-2021-insid...) is now up. They're impressed.

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