How can it not be about Corona when you see MR images above where this faceting artifact doesn't exist and there are smooth environment reflections all the way across the mesh with no changes to geometry or smoothing groups?
Looking at your file, you changed it to editable poly and broke it into separate objects. These game assets can't be either of those and the question at the beginning was can I get better results than this faceting WITHOUT changing anything about the model because if I did have to make changes, it would defeat the purpose, which was can I do nice renders of a bunch of game assets without doing surgery to each of them.
I can think of several ways to fix this problem if I'm willing to make changes to the geometry. Also, clearly it's an issue that's only going to be noticeable on a low-poly editable mesh, which makes it an edge case to begin with.
As I said, I'm mostly just curious to see if there's a way around that problem with no changes to the model just because I'm curious at this point and it's a good excuse to poke at Corona, trying to solve a problem is a good and quick way to play with everything and see how it works.
Anyway, Romullus and Maru, unless you're also curious about it, I don't think there's enough value to keep pursuing it - very few people are ever going to run into this issue. Corona is a high quality rendering engine for high quality models, not insanely low poly editable meshes designed for very old game engines.
