This is my current mesh:

enter image description here

I want to turn the square hole into this shape:

enter image description here

I tried ⎈ CTRL + ⇧ Shift + B to bevel the vertices, and it gave me this:

enter image description here

But the problem is when I scrolled up, instead of giving me a smooth circle-like bevel, it simply subdivided the diamond:

enter image description here

How can I create the circle-like shape I desire here?

  • $\begingroup$ There are 18 blades try to make single blade and then array and rotate it $\endgroup$
    – atek
    Commented Apr 29, 2017 at 4:14
  • $\begingroup$ I don't know what you men by that @ateks? $\endgroup$ Commented Apr 29, 2017 at 4:24
  • $\begingroup$ i want to say that there are 18 side so make 1 side then rotate $\endgroup$
    – atek
    Commented Apr 29, 2017 at 4:25
  • $\begingroup$ @Accumulator are you gonna use Subsurf Modifier for this? $\endgroup$
    – cgslav
    Commented Apr 29, 2017 at 7:38

2 Answers 2


I'll present you method based purely on quad topology.


It's a little bit manual work, but nothing is worth more then nice quad base topology.

Make sure you have enabled F2 addon in User Preferences as it will speed up last step. You certainly don't need it. It will be just easier.


  1. Delete 3 bottom vertices.
  2. Add a Circle and set Vertices to 8/12/16/20/24... and so on. Just to have straight horizontal vertices along Circle. I have used 16 in this example.
  3. Scale it down approximately between existing shape then scale it up with Vertex Snap and hover closest vertex. I've done it holding CTRL while scaling.
  4. Remove top part of the Circle.
  5. W > Remove Doubles to "merge" Circle with existing shape.
  6. Select 2 vertices on one chosen side right before empty face, move mouse cursor to the other side and hold F (F2 addon).

I have two other methods on my mind but this seems to be the cleanest one so far.


I rather like @LukeD's answer, but I started writing this last night, and I like that it starts from where @Accumulator left off:

I'm no expert with the bevel tool, so this might not qualify as the answer to your original question, but the question I saw at the end was how to produce the desired shape. That I think I have a good answer:

For reference, I've labeled the points in your last screenshot: All labeled vertices

  1. Select and delete vertex A and vertex D.
  2. Select vertices L and R, and snap the 3D cursor to the selection, so it should jump to C.
  3. Select vertices L and B, duplicate them with [Shift]+[D], and rotate them 45 degrees around the 3D cursor.
  4. Add vertices L and B to the selection, duplicate them with [Shift]+[D], and rotate them 22.5 degrees around the 3D cursor.
  5. Steps 3 & 4 gave you 6 new points. These are where we will move points E, F, G, J, K and M to using this procedure 6 times:

    A. Select the new vertex location.

    B. Add the original vertex to the selection.

    C. Merge the vertices to the first point.

  6. (Optional) move vertex H and vertex N slightly closer to C, to ensure all quads are properly convex.

This diagram should give an idea what the final quads would look like:

final mesh topology (on left side)

I've been away from blender for a few weeks, so feel free to add any hotkeys I may have forgotten. I hope you find this helpful.


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