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I have a cylinder with a hole in it. The top face of it should be a flat plane but it isn't, even if there are no edges on it which could cause the unevenness.

I inserted an additional edge (the marked one) so that you could see what I mean. enter image description here

Why isn't the face a flat plane and how can I make it flat? I tried to delete the top face and replace it with "fill hole" but that is not possible.

10 Replies
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theoretisch
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    A polygon with more than 3 vertices won always be collinear, So you have to make sure it is flat, Use the flatten tool in the Loop tools addon (select the face, press W > loop tools > flatten) which is the easy way. – Omar Emara Dec 01 '16 at 11:32
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    It's also possible to scale it along normal (with Transform orientation set to Normal press S > Z > Z > 0). Related - http://blender.stackexchange.com/questions/7729/how-to-flatten-a-face-to-avoid-distortion-make-an-ngon-planar – Mr Zak Dec 01 '16 at 12:01
  • @Omar Ahmad: I tried to download it but the website of this addon is REALLY confusing and unstructured for my opinion. I was not able to find anything.

    @ Mr Zak: A very good shortcut! But my tube (cylinder with whole) is concave (you can't see that on my picture). And if I apply your shortcut it isn't concave anymore.

    Nevertheless thank you to both of you!

    – theoretisch Dec 01 '16 at 13:23
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    @theoretisch Loop tools is already with blender, you just have to enable it from the addon panel. – Omar Emara Dec 01 '16 at 13:34

1 Answers1

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I found a way to make it flat.

There is a second fill option (not fill holes) with ALT + F or under Mesh -> Faces -> Fill (with tries)

With this it worked.

EDIT: There is a third fill option (GridFill) with Ctrl + F (with quads)

Thanks to Mr Zak in the comments.

theoretisch
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  • Looptools addon is present in Blender by defaullt, you just need to find and activate it in User Prefs.. although its result might be similar to scaling. I suggest filling those faces with quads like with GridFill (find it in Ctrl+F menu). I also think that answering to comments is best in comments, to keep answer clean. – Mr Zak Dec 01 '16 at 13:09
  • Ah ok I was unaware about this, thank you. So the difference between Gridfill Ctrl+F and Alt+F that the former makes quads and the latter makes tries? I will edit the answer. – theoretisch Dec 01 '16 at 13:23
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    Generally yes, see Fill and GridFill. The latter creates quads when possible. – Mr Zak Dec 01 '16 at 13:40
  • Ok I tried it, but in my case I think I have to use Fill. GridFill didn't work. – theoretisch Dec 01 '16 at 14:06
  • GridFill in this sense is more complex as it relies on existing topology (amount of vertices which form edges you fill). This amount should be even and roughly (ideally equal) the same on the both edge loops; see example. First example won't be closed; second will. – Mr Zak Dec 01 '16 at 14:41
  • Thank you, probably my verts at the inside of the cylinder are not the same number than at the outside. It seems that at the inside are much more. So it's not possible to make quads from that. But luckily I don't need quads, because its almost finished. – theoretisch Dec 01 '16 at 14:53