Overlapping UVs in Substance are functional, yet not compatible with post-unwrap triangulation
TL;DR (How can Substance tell whether or not I unwrapped in Blender again after triangulating an overlapping UV? Overlapping UVs are fine. Overlapping triangulated UVs are fine. Changing UV triangulation is fine.
Only on overlapping UVs, changing UV triangulation after the unwrap in Blender is NOT fine.)
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After a lot of testing I have deduced the following:
Substance works fine with an overlapping quad-based UV as well as a triangular one. There is a lot of conflicting advice online regarding this matter, but I have had no issue with this mesh before attempting to fix a triangulation error.
Triangulating a quad UV (or triangulating any quad on the UV) without again unwrapping (destroying the UV map) will result in errors when imported into Substance.
Circled area is the only part of the UVs overlapping on the mesh. Error was not present before triangulating.
If the mesh is not again unwrapped after any quad on overlapping islands is triangulated, this error will occur. This does not occur when UVs are not overlapping or if the mesh is unaltered.
So here's a real example of this issue: I've got a huge dent in my mesh.
But I have already spent much time carefully placing the UVs and texturing in substance. I cannot unwrap this mesh in Blender again. However, correcting this dent by defining how these quads will be triangulated results, again, in this error.
Ruining a carefully placed UV map just to fix a triangulation error is not practical.
What I'm not understanding is how Substance can even tell whether or not I unwrapped in Blender again after triangulating.
The UV could be configured the exact same way in both cases, but only one would work. Do I really have to waste texture space by NEVER overlapping UVs? SURELY there must be some way to convince Substance that I performed the unwrapping ritual without destroying everything.
Replies
https://drive.google.com/file/d/1TMoBroPlt2KbGN9sp4hYfky_M7qvJ_v4/view?usp=sharing Here's a chunk of the mesh demonstrating the issue if you upload it into Substance.
If anyone can find a way to correct this thing that does not involve re-unwrapping it, I'd be very thankful.
Add a seam, and move your UVs off one entire UV set.
Wow man. I think this is what everyone meant by "offset by 1".. ugh. I feel so dumb.
I thought they meant offset by 1 pixel. This was tremendously helpful and I was able to fix the dent right up in an instant. Just fantastic. Thank you so much.