I am sure that by now (after many hours of reading the unreal engine documentation), we all can agree that we would usually need 2 UV channels for our game assets:
1[SUP]st[/SUP] UV channel is usually for our standard baked textures to be mapped from, you can overlap UVs (only if necessary) and can go beyond the 0-1 space
2[SUP]nd[/SUP] UV channel is for the lightmap, and the UV cannot be overlapping and must be within the 0-1 space.
My question is, if for example I have a sofa, the main portion of it which requires a standard fabric material, is a lot/huge, whereas the fabric texture is small, therefore I have to enlarge the polygon in the UV mapping, so that the size of the fabric texture fits the sofa. But then it will mean that I have to go beyond the 0-1 space. If I were to keep it all within the 0-1 space, texture quality will suffer and going to a higher res map is not really a good thing to do.However, it works fine, as there is a 2[SUP]nd[/SUP] UV channel for the lightmap. I think this tutorial explaining texture density pretty much covers what I’m to say.
But what if I want to texture that way (outside 0-1 space and overlapping UVs), so that I can reuse my seamless fabric material in UE4, but I want to add an AO map and normal map for my sofa? How will I proceed in the material creation for my sofa? Can I, for example, assign my AO and normal map using the 2[SUP]nd[/SUP] UV channel since it is not overlapping and all within 0-1 space, and also because the 1[SUP]st[/SUP] UV channel will not work for AO and normal map? Or do I have to, no matter what, all maps be used through the first UV channel? Or is there another way around to tackle this problem? Thank you in advance.