How can I smooth the top side of this ring? I want to smooth the top side of this ring:




This is how it looks like after rendering:


The mesh of the top side of the ring is very obvious in the rendered image and basically this is my problem.

I am a beginner in Blender but I have tried everything I know. First off, I have made the selection of the top side of the ring manually in edit mode because couldn't find an easier way. Then, I have tried to subdevide the selection but it won't subdevide anything except for some faces. I have tried ctrl+R to make cuts but it doesn't work.

The ring is the result of an extruded 2D vector and then sliced vertically using Knife project tool and then bent 360 degrees using simple deform modifier

My question is how can I smooth just the top side of the ring without the edges?
I guess you have these 2 solutions:


Smooth your object in the Tools panel, and in the Properties panel > Data > Normals, enable Auto-Smooth, set the value under which the angles smooth.





Create a bevel all along the angles, thin enough to keep them sharp, it may need a bit of knife work if you have triangles or ngons. After that, smooth your object in the Tools panel, and give it a Subdivision Surface modifier. If you're supposed to 3D print the object, I guess you just need to apply the Subsurf.