How to smooth the sides of curved objects


I have a question with a probably simple answer, but I didn’t find any simple solution although I looked for an hour in Blender.

Let’s say I want to create an object looking like the letter “O” in 3D. It’s just an example, so I can’t use a text object.

Well, I recreate the front of this O with a couple of faces and extrude all the faces to get the third dimension.

Now I’d like to smooth the new faces that were created from extruding the front so that the O looks really round and not like an n-gon where n is the count of faces I used to create the front.

I tried the “Smooth” option in the “Object Tools”, but then the colouring looked odd (although all normals point outwards) and it seemed then the edges between side and front were smoothed too.

I tried to apply the modifier “Subdivision surface” but then everything got subdivisioned not only the side faces.

Is there a way to just smooth the side face (the extruded ones) and leave the explicitely created faces (the front and back) as they are?

Thank you for your help.

Enable smooth shading. Then to give the crisp edge between the front face and sides you can add an Edge-Split modifier (you can make selected edges as sharp with Ctrl+E or adjust the angle value in the slider) or you can bevel the edge (Ctrl+B) or you can add edge loops near the edge. If you use the subdivision surface modifier you can crease selected edges with Shift+E

Thank you, the Edge-Split-Modifier did the trick!

[quote]I tried the “Smooth” option in the “Object Tools”, but then the colouring looked odd (although all normals point outwards) … [/i]

I have noticed this, too, when using “Smooth,” and I’m not quite sure what to make of it. A large, flat, n-gon area nevertheless looked “bumpy” in the render, as though there were shadows across it here and there, or like the surface was warped. Would edge-splitting have made a difference?

The specific object I’m talking about represents a large piece of cast metal, part of an industrial machine, and the surfaces of it are n-gons, with a bevel modifier applied to the whole thing. I didn’t spend a lot of time on it but I’m still a bit puzzled …?