I've got a little but very annoying problem with material smoothing...
material with "smooth" on

same material with "smooth" off

The object is a basic cube subdivided with subdivision modifier active. No matter how much I subdivide it, the result is the same... I even tried to use multi-resolution modifier but no change... I also tried to apply the modifier before render, recalculate normals and all I could think of but I can't seem to find a solution.
Anyone getting the same problem or is there something I missed here ?
Thank you for any solutions you can bring up, I'm pretty stuck with that and I have short deadline for the current project I'm on... :s