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I drew a bracket-like shape with Bezier curve and then made 3D object from it by rotating with Screw modifier.

I was thinking I will get perfect object, but my object appeared non-uniformly colored:

enter image description here

As you see on side projections, ends of the shape are absolutely flat, but despite this, they are shaded non uniformly, like automobile tires.

How to fix that?

Normals are looking as follows

enter image description here

and after Recalculate it turns into

enter image description here

i.e. normals got good, while shading is still non-uniform...

UPDATE

I found I can make faces Flat with

enter image description here

Should I apply this explicitly for each face?

Was I able to do something to the curve before applying Screw, to avoid these manual operations?

UPDATE

Video proof of operations to create initial object (before starting to make faces flat):

https://youtu.be/5YVsgqo03bc

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    $\begingroup$ Try to flip the direction of the normals, Ctrl+N or Ctrl+Shift+N, and add edge split mofdifier $\endgroup$ – Denis Nov 16 '15 at 7:01
  • $\begingroup$ if you want a help about your workflow from curve to shape, you should document a bit more... a screw modifier cannot be applied on curves, so, what you did exactly? converted curve to mesh berfore screw? or converted to mesh the screwed (pun intended) curve ? $\endgroup$ – m.ardito Nov 16 '15 at 12:53
  • $\begingroup$ @m.ardito was not converting to mesh. Just tried to apply Screw to Curve again right now and succeeded. I have Blender 2.76 $\endgroup$ – Dims Nov 16 '15 at 13:07
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about the non uniform shading in your pictures, it could also be that your starting curve was not properly aligned /centered on the screw axis, so the screw has repeated a tilt that was in you curve, hence the shading.

I roughly created this in a similar way, and I get no fuzzy shading:

enter image description here

without applying the modifier, you can convert this to 3d mesh using ALTC (the modifier will be removed, the effect is just like if it was applied) - I had to recalc the normals, after, anyway.

[edit] the "peak" you see is because I fastly drew a curve in this shape:

enter image description here

anyway another way is draw the bezier, convert it to mesh, and then screw - using "calc order" in the modifier seems to give better normals, to me.

anyway even with a better "curve" with straight angles like this

enter image description here

i get no "peaks" but the weird shading comes back. It seems due to the normals in that area

enter image description here

one way to fix this is to get less straiht angles there, either using a somewhat smoothed starting curve (as my first one) or after applying the modifier, adding some loops, on both sides:

in edit mode CRTLR2

enter image description here

before applying, scale on X

enter image description here

then on the circle CRTL R

enter image description here

before applying, scale a bit toward the center enter image description here

and now it seems much better

enter image description here

[edit2] after seeing you video, I got why is different: since your starting curve is closed, screw modifier gives weird shading con the "front circle" face. Again, adding two loops near the inner and outer circle edges gives a much better look.

enter image description here

here the result, flat and smooth shaded:

enter image description here

enter image description here

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  • $\begingroup$ You probably don't see an effect because you have a lot of radial subdivisions on ends. Anyway, you can see some "peak" at the center. $\endgroup$ – Dims Nov 16 '15 at 13:13
  • $\begingroup$ See my video please: youtu.be/5YVsgqo03bc $\endgroup$ – Dims Nov 16 '15 at 13:33
  • $\begingroup$ I've seen it, and got why is different than mine: the curve is closed, and screw behaves differently. Anyway you can apply the "add loop" trick I added above, I'll add another image for that case... $\endgroup$ – m.ardito Nov 16 '15 at 14:00

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