Second UV workflow

Nerdicon3000

I have been looking for a tutorial showing how to use a second UV channel workflow. I see new games using it. I think it's like mixing tiling textures and trim sheets without adding geometry, not 100% sure really. It just looks really powerful. Can anyone help point me in the right direction?

V!nc3r

Usually it's used for lightmaps (example on Unity, or from polycount wiki, also on Unreal [1] [2]) . Talking about Unity, note that I'm not sure about that, maybe the detail maps are using UV2? (if a Unity user can confirm)

srsface

In addition to lightmaps and detail maps, you can basically make any part of the model have exactly the UVs that you want a specific texture to have. It's useful when blending between different textures/material sets with whatever masks or vertex colors.

Least in Unity HDRP's built-in Lit shader you can make use of the different UV channels to blend between totally different looking textures and ensure the end result always looks good. For example, one way to make trees is to have a unique texture for the base of the tree and then a tiling texture for the trunk, and then blend the transition between them to hide the seam. The trunk is easy to unwrap with simple cylindrical UVs, but for the base the cylindrical UVs might introduce a lot of deformation. Instead you can assign different UVs to different channels of the mesh for these two textures, and then assign the correct UV channel for each part of the mesh in the shader.

It's a little hard to explain in words only, so for examples of the above you could take a look at the Fontainebleau photogrammetry demo assets by Unity if that's what you use.

Nerdicon3000

I was thinking more like this.
https://www.youtube.com/watch?v=6g5YKzKxX3U
I see guys using face vertex normals and medium poly workflow with just tiling textures and then using a trim shit and floating geometry to give a really nice effect of detail for cheap, but I have also seen the technique used with a multiple UV sets so that you don't have to add the extra geo and it seems more efficient. I'm just looking for a tutorial that goes into more detail and maybe creates a whole scene. It's like the star citizen workflow but with multiple UV sets.

Alex_J

Take a look at microsplat on the unity store (it's free) to get an idea of some other things you can utilize second UV channels for. Macro/micro textures, height based blending, etc.

Eric Chadwick

https://polycount.com/search?Search=trim+sheet

Also
http://wiki.polycount.com/wiki/MultiTexture#Trim_Sheets