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UE5 Nanite in WebGPU

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Re: UE5 Nanite in WebGPU

#61

Post by jiggawatts »

Animats wrote: post #17

Oh, nice. Third party implementations of Nanite playback. Nanite is a very clever representation of graphics meshes. They're directed acyclic graphs rather than trees. Repetition is a link, not a copy. It's recursive; meshes can share submeshes, which in turn can share submeshes, all the way down. It's also set up for within-mesh level of detail support, so the submeshes drop out when they're small enough. So you can…

I read through the papers and my impression was that the biggest gains were from quantised coordinates and dynamic LOD for small patches instead of the entire mesh.

The logic behind nanite as I understood it was to keep the mesh accuracy at roughly 1 pixel precision. So for example, a low detail mesh can be used with coordinates rounded to just 10 bits (or whatever) if the resulting error is only about half a pixel when perspective projected onto the screen.

I vaguely remember the quantisation pulling double duty: not only does it reduce the data storage size it also helps the LOD generation because it snaps vertices to the same locations in space. The duplicates can then be eliminated.

Re: UE5 Nanite in WebGPU

#62

Post by sva_ »

pjmlp wrote: post #50
Twirrim wrote: post #42

Earlier quoted context omitted.

It's not working for me on Chrome under Linux, nor on Android, for what it's worth (though Firefox is what I use for practically all my browsing needs). Something really odd with their detection logic.

WebGPU is not supported on Linux, and it won't for the foreseeable future. On Android you should have at least Android 12, with good enough Vulkan drivers, not blacklisted.

> WebGPU is not supported on Linux, and it won't for the foreseeable future.

A lot of it runs fine with a flag.

Re: UE5 Nanite in WebGPU

#63

Post by gmueckl »

Animats wrote: post #53
Jasper_ wrote: post #43

Earlier quoted context omitted.

I'm not seeing what you claim to be seeing in that demo video. I see a per-triangle debug view, and a per-cluster debug view. None of that is showing repetition.

If there wasn't repetition, you'd need a really huge GPU for that scene at that level of detail.

I don't want to estimate storage space right now, but meshes can be stored very efficiently. For example, I think UE uses an optimization where vertex positions are heavily quantized to just a few bits within the meshlet's bounding box. Index buffers can be constructed to share the same vertices across LOD levels. Shading normals can be quantized quite a bit before shading artifacts become noticeable - if you even need them anymore at that triangle density.

If your triangles are at or below the size of a texel, texture values could even be looked up offline and stored in the vertex attributes directly rather than keeping the UV coordinates around, but that may not be a win.

Re: UE5 Nanite in WebGPU

#64

Post by jms55 »

Animats wrote: post #53
Jasper_ wrote: post #43

Earlier quoted context omitted.

I'm not seeing what you claim to be seeing in that demo video. I see a per-triangle debug view, and a per-cluster debug view. None of that is showing repetition.

If there wasn't repetition, you'd need a really huge GPU for that scene at that level of detail.

Not necessarily. Nanite compresses meshes (including in-memory) _very_ heavily, and _also_ streams in only the visible mesh data.

In general, I wouldn't think of Nanite as "one thing". It's a combination of many, many different techniques that add up into some really good technology.

Re: UE5 Nanite in WebGPU

#65

Post by jms55 »

pcwalton wrote: post #58
Animats wrote: post #17

Oh, nice. Third party implementations of Nanite playback. Nanite is a very clever representation of graphics meshes. They're directed acyclic graphs rather than trees. Repetition is a link, not a copy. It's recursive; meshes can share submeshes, which in turn can share submeshes, all the way down. It's also set up for within-mesh level of detail support, so the submeshes drop out when they're small enough. So you can…

> Making a nanite mesh is complicated, with a lot of internal offsets for linking, and so far only Unreal Engine's editor does it. meshoptimizer [1] is an OSS implementation of meshlet generation, which is what most people think of when they think of "Nanite's algorithm". Bevy, mentioned in a sibling reply, uses meshoptimizer as the generation tool. (Strictly speaking, "Nanite" is a brand name that encompasses a larg…

Small correction: meshoptimizer only does the grouping triangles -> meshlets part, and the mesh simplification. Actually building the DAG, grouping clusters together, etc is handled by Bevy code (I'm the author, happy to answer questions).

That said I do know zeux was interested in experimenting with Nanite-like DAGs directly in meshoptimizer, so maybe a future version of the library will have an end-to-end API.

Re: UE5 Nanite in WebGPU

#66

Post by jms55 »

It's been mentioned a couple of times in this thread, but Bevy also has an implementation of Nanite's ideas (sometimes called Virtual Geometry). I'm the author of that, happy to answer questions :)

As for this project, Scthe did a great job! I've been talking with them about several parts of the process, culminating in some improvements to Bevy's code based on their experience (https://github.com/bevyengine/bevy/pull/15023). Always happy to see more people working on this, Nanite has a ton of cool ideas.

Re: UE5 Nanite in WebGPU

#67

Post by KronisLV »

I wonder how other engines compare when it comes to LODs and similar systems.

Godot has automatic LOD which seems pretty cool for what it is: https://docs.godotengine.org/en/stable/tutorials/3d/mesh_lod...

Unity also has an LOD system, though despite how popular the engine is, you have to create LOD models manually: https://docs.unity3d.com/Manual/LevelOfDetail.html (unless you dig through the asset store and find a plugin)

I did see an interesting approach in a lesser known engine called NeoAxis: https://www.neoaxis.com/docs/html/NeoAxis_Levels.htm however that engine ran very poorly for me on my old RX580, although I haven't tried on my current A580.

As far as I can tell, Unreal is really quite far ahead of the competition when it comes to putting lots of things on the screen, except the downside of this is that artists will be tempted to include higher quality assets in their games, bloating the install sizes quite far.

Re: UE5 Nanite in WebGPU

#70

Post by astlouis44 »

Here's an actual implementation of UE5 in WebGPU, for anyone interested.

Just a disclaimer that it will only work on WebGPU-enabled browser on Windows (Chrome, Edge, etc) unfortunately Mac has issues for now. Also, there is no Nanite in this demo, but it will be possible in the future.

https://play.spacelancers.com/

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