This problem has been annoying me for the last year so I hope someone has a few ideas on it... In order to get rid of tessellation in models you go to.. Tools>Options>Performance>Image Quality and put the top slider to a maximum, check 'optimize edge length'. Often when I do this I still have tessellation in the model (doesn't matter what size the curve is that I'm looking at). I need to get rid of this as I'm doing a close up render which should show a nice curve. Hope someone can help, Thanks.