What I was getting at is that it appears to me as if Phong/smooth shading may not be implemented as well in Firefly as it is in the P4 renderer and isn't very compatible with bump mapping, thus the poly lines (which is probably so obvious to you that it isn't worth mentioning).

Does this happen with every combination of lighting?  I've noticed that I sometimes get poly lines REGARDLESS of material, and it may be that it's just more obvious in your example here.

Quote - I can also demonstrate that the problem exists even WITHOUT bump. It's just much more subtle but its there all the time. It becomes especially obvious after running a cloth simulation.

^^ or that.

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