Proper practice for lightmapping and UVs?

In the past when making assets, I’ve frequently layered UVs on top of eachother to save space if the objects in question should be symmetrical–such as bolts on the side of a bucket that would all look the same, or mirrored halves of a symmetrical object. When my team started incorporating lightmapping into our work, I figured out pretty quick how that messed with lightmaps. It was easy enough to fix just by generating new, un-overlapping UVs for objects and having the lightmap pull from that instead of the old UVs the texture and other maps use, but is this good practice? Am I still okay to have UV pieces layered on eachother for efficiency’s sake for texturing and then make a different UV map for lightmapping, or should I only have one non-overlapping UV layout that gets used for everything?

This is fine, Unity generates a second UV channel for lightmapping anyway (based on the 1st UV if you don’t supply a second, otherwise it’s based on the 2nd), so you’re ending up with 2 uv channels regardless of whether you supply one or two.

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Good to know, thank you. So does this mean that, of the four UV channels an object can have, one of them is always reserved for lightmapping?

I am not 100% sure if anything is different for HDRP, or if there is a recent change I’m unaware of, but I think so, yes.

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