Whenever I make an object smooth (not smooth in the edit menu, but in “Link and Materials” menu), the lighting goes a bit funny. The edges of objects go very dark, and faces next to extruded faces go very dark, and look… funny. Since I can’t explain it very well, below is a picture of a cone with a small extruded part.
Remember that the cone is perfectly round. Can anyone offer a solution?
Try recalculating the normals, in edit mode with all the vertices selected press ctrl+N.
Mystery
Nah, didn’t work. Thanks for trying, anyway.
SetSmooth is an optical illusion, it doesn’t actually “smooth” anything. As such, it sometimes has difficulties dealing with things that aren’t almost smooth to start with. You’ll notice, for example that edges which you might expect to “round-off” when smoothed, still show the linear edges. To get some idea of how weird the results can be, just SetSmooth the default cube and render it.
You can try using AutoSmooth and mess with the angle parameter for good results or, for quality results, use a subsurf modifier first then add additional geometry as required to deal with “shaper” edges. Then SetSmooth to polish it off.