Two UVs workflow using Trim Sheets?

the_dlearner

Found this from Alex Senechal, amazing work ArtStation - Premium Tech Industrial SCIFI Trims and Floor Set - GUMROAD but curious he mentions a two UVs workflow with Trim Sheets. Does anybody know how this works? Or if there's another post in here that speaks about it - couldn't find anything myself.

Benjammin

It means using a second UV channel that's unwrapped/scaled differently. So you might have a channel with everything packed uniquely for baking, then a second channel for doing repeating details like trims. 

the_dlearner

Benjammin said:

It means using a second UV channel that's unwrapped/scaled differently. So you might have a channel with everything packed uniquely for baking, then a second channel for doing repeating details like trims. 

oh, so that's it? thought it was to do some blending or whatever in between strips/trims lol, because, im not sure there's any other advantage aside from saving time when baking since you already have the packed channel UVs?

poopipe

It's worth mentioning that unless your engine supports a separate set of tangents per UV set (most don't) you are restricted in how you can UV the object

if you rotate shells or scale shells non-uniformly between UV sets it will result in normal map artefacts.

you can hack your way around this in unreal but it's not a perfect solution

Benjammin

the_dlearner said:

Benjammin said:

It means using a second UV channel that's unwrapped/scaled differently. So you might have a channel with everything packed uniquely for baking, then a second channel for doing repeating details like trims. 

oh, so that's it? thought it was to do some blending or whatever in between strips/trims lol, because, im not sure there's any other advantage aside from saving time when baking since you already have the packed channel UVs?

Its not about saving time, its about texture re use. If you texture something with just the trimsheets, it'll look like its been textured with trim sheets. But if you combine that with baked ambient occlusion/curvature, which maybe drive some dirt and wear effects in your shader you're starting to get somewhere. 

the_dlearner

Benjammin said:

the_dlearner said:

Benjammin said:

It means using a second UV channel that's unwrapped/scaled differently. So you might have a channel with everything packed uniquely for baking, then a second channel for doing repeating details like trims. 

oh, so that's it? thought it was to do some blending or whatever in between strips/trims lol, because, im not sure there's any other advantage aside from saving time when baking since you already have the packed channel UVs?

Its not about saving time, its about texture re use. If you texture something with just the trimsheets, it'll look like its been textured with trim sheets. But if you combine that with baked ambient occlusion/curvature, which maybe drive some dirt and wear effects in your shader you're starting to get somewhere. 

Understood, thanks a ton. So prob the second UV is set to cube projection and I define that UV to be used by the ambient occlusion/curvature/roughness/metallic maps so that if i cut a decal within my geo it doesn't look off

Eric Chadwick

Cube projection is really fast and easy, but it makes terrible cuts across anything not rectilinear.

Better to copy and repack existing UVs, making sure not to rotate nor non-uniform scale them.

the_dlearner

Eric Chadwick said:

Cube projection is really fast and easy, but it makes terrible cuts across anything not rectilinear.

Better to copy and repack existing UVs, making sure not to rotate nor non-uniform scale them.

Yeah im just repacking, works waaaay better