Is there any roadmap or idea submission about support for Geometry Shaders in Shader Graph?

[misty nimbus]

Wondering if there's any planned support since it would be nice to add geometry shader features to my terrain shader

[agile flax]

No indication of that ever happening
Afaik geometry shaders are vestigial technology which GPU manufacturers are no longer developing or actively supporting either
The same role is filled by compute shaders, and in Unity also Render Graph and VFX Graph

[misty nimbus]

Ooh, what would be the alternative to generate extra data on the shader?

Mesh shaders?

[misty nimbus]

I would like to generate triangles and vertices on the shader side so i can get dynamic/smoother data on the ground

[agile flax]

I think you'd consider compute shaders for generating procedural geometry
Or maybe tessellation shaders

[misty nimbus]

Okay, correct me if I'm wrong but isn't a tessellation shader a geometry shader?

I was thinking about that

[agile flax]

They are a wholly different rendering stage, as far as I understand

Though there's unlikely to be SG support for tessellation either because it seems to be another GPU feature that's falling out of favor
Particularly so because in most situations you can achieve the same thing using various types of LOD crossfading, in a much more batching-friendly way

[peak linden]

Those are D3D12's successor for geometry shaders, yeah.

I have never touched them myself

[misty nimbus]

Mmm, can you do LOD crossfading of an area around a player of x radius? I'm not sure how can I crossfade lods of sections of a mesh like that.

[agile flax]

No, but it's not usually an issue to have multiple meshes

Huh, I vividly recall a roadmap entry about lod crossfading that works by sliding vertices between lod levels so the geometry morphs, similar in appearance to tessellation, and unlike the typical dithered crossfade
But now I can't find any evidence of that feature ever existing
With the exception of speedtree lod crossfading which works exactly that way but apparently not for typical meshes

[misty nimbus]

Do you have any reference on that technique on how it works?

[urban magnet]

This sounds like a typical use case for tessellation.

Tessellation: add more triangles to what you already have
Mesh shaders: you control how triangles are generated and processed from scratch (in chunks)

It's true that tessellation is old and falling out of favor but your use case is a great fit for it, and making a full meshlet pipeline is way higher effort.

[misty nimbus]

But isn't tessellation made via the use of Geometry Shaders?

[urban magnet]

No, it’s done through the three tessellation stages:

https://learn.microsoft.com/en-us/windows/win32/direct3d11/direct3d-11-advanced-stages-tessellation

I don't think geometry shaders were ever widely used. Tessellation definitely was (if only for a short while). Especially CryEngine went mad with their top secret tessellated toad technology

[misty nimbus]

I see, thank you!

Do you know if there's a way to do that in URP or via the Shader Graph?

[urban magnet]

Yeah, I did it in URP ages ago. You'll have to look it up though.