Normal map noise problem

Grimmolds

I am trying to create a Borderlands game-ready character, and I decided to use normal maps to preserve details from my high-poly model. It worked good, except for one thing: these strange curved lines. I Don't know the cause of them. 
I made them with Zbrush...you can see those lines in the red rectangle in the second image. 
They appear with every shader I use, so it's not AiToon fault. 

Eric Chadwick

See this
Sticky Of Bit Depths, Banding and Normal Maps

Grimmolds

Well thank you very much for you fast response. Interesting, it seems exactly the banding problem described there. The problem is that Zbrush can't bake over 8 bit normals, so...well it wasn't totally my fault. Thank you very much again. 

musashidan

Last piece of advice for the night...... don't EVER bake normals  in Zbrush. Poor quality, crazy tangent basis, way too many superior alternatives these days.