I'm making this shape which is just a cylinder with a curve modifier on it.

enter image description here

I can't seem to figure out why you can see the subtle bends in the cylinder. I've rendered it multiple times with varying subdivision render levels, and I've even tried increasing the number of loop cuts from 100 all the way to 400+, and I can still see those bends/vertices/loop cuts.

I must be overlooking something. Can anyone help me out? I'll post my .blend in a moment.

edit: I'll note that I did apply shade smooth and autosmooth normals, and the problem persists. I currently have the subd render level to 3.


  • $\begingroup$ did you do shade smooth on your model? $\endgroup$ – ETHAN DAY Oct 26 '20 at 15:05
  • $\begingroup$ Yeah, shade smooth and autosmooth normals. $\endgroup$ – n0ah Oct 26 '20 at 15:13
  • $\begingroup$ In the Subdivision Surface modifier, the subdivision for viewport is only 1, does it change something if you change to 2? $\endgroup$ – moonboots Oct 26 '20 at 15:13
  • $\begingroup$ Nope. I just tried re-rendering it and it's the same. $\endgroup$ – n0ah Oct 26 '20 at 15:14
  • $\begingroup$ maybe try selecting everything in edit mode, and then subdivide it a bunch? $\endgroup$ – ETHAN DAY Oct 26 '20 at 15:18

The imperfections are inherited from the curve used in the curve modifier. Select it, go to edit mode, select all and then search(f3) for Set Spline Type operator and set to NURBS:

enter image description here

You will also be able to control the resolution of it in the curve properties tab, but default 12 should be fine.

Or you could also solve the problem by moving the subdivision modifier below the curve: enter image description here

I would recommend to do both - make the curve smooth and also use the subdivision modifier in the right order.

Just to clarify: by "right" order I mean probably the more efficient way - first modify the less dense geometry by curve modifier requiring less computation and only then smooth it by subdivision also increasing the density. I might not know some of the context to use such strong words as "right" ;)

  • $\begingroup$ Well hot damn... The NURBS change did it! Thanks a ton! Although I guess I don't quite understand curves that well. NURBS have more control than Bezier? $\endgroup$ – n0ah Oct 26 '20 at 15:36
  • 1
    $\begingroup$ They are only different ways to control the curvature. I think its just easier to do with NURBS in this case, but you might as well use bezier and set vector handles to automatic. I don't think there is much difference, whatever is easier for you to work with. I tend to like NURBS a bit better, but it's not based on any facts, just personal preference so use whatever works best for you. The true issue was the sharp corners on poly type curve. $\endgroup$ – Martynas Žiemys Oct 26 '20 at 15:44

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