Hi Guys,
I am facing problem with normal map which i have exported from zbrush and applied it to maya base mesh, while rendring in maya black line comes on edges as seen in the images. I put the snapshot of zbrush normal map setting and maya setting while rendring.
Please help me out with this problem…
Thank you,
Just saying… ZBrush 4R4 P2 is a free upgrade. 
If I had to guess, I’d say you used a primitive box (instead of exporting the base mesh from ZBrush) and chamfered its edges, which effectively messed up its UVs.
So either use the base mesh (SubDiv 1) from ZBrush, or don’t chamfer the edges.
Are you using Mental Rays approximation editor to smooth? Also I would turn on adaptive in Zbrush… You can also try adding a displacement map for the first couple of levels for capturing the shape then use a normal map to capture the details in the upper levels.
Bake the map in Maya; a synced tangent basis can do wonders sometime.