Anytime you need to add additional subdivisions to only certain edges of a circle (not all edges) you wind up with a shape that's no longer circular when the sub surf mod calculates the curve between the newly added vertex and the original vertices.

Logically it seems that there should be a way to determine where that new vertex needs to be to make the resulting sub surf line appear circular. Unfortunately, as a human, it's hard for me to pinpoint that exact location by eye.

Is there a tool or command that re-circularizes the shape once I add my subdivision to my circles edge? Am I thinking about this the wrong way such that there's an alternative path that fixes the problem without this tool?

Thanks in adv.

Circle has been deformed by additional vertices

Hexagon creates circle w/ sub surf modifier

Left Hexagon is sub divided only on top Edges. Right Hexagon is sub divided on all edges


2 Answers 2


If I understand well, your issue is to recalculate edges/vertices to be circle shape after adding more cuts, maybe this answer could help. Anyway if that the case, you should first outline well your circle mesh using as less as possible edges, or add circle mesh instead outlining it by hand.

  • $\begingroup$ The circular mesh was added previously. I simply added additional vertices where I felt they needed to be on the outline of the mesh. The link you provided moved all vertices where I'm simply looking to move the ones that were newly added to the place that they needed to be. $\endgroup$ Jan 23, 2019 at 15:15
  • $\begingroup$ Ok now I get it, so, how I will do this is first outline circle mesh first and after that, if I need more cuts, I would add with subdivide tools (that one in left panel) $\endgroup$ Jan 23, 2019 at 15:18
  • $\begingroup$ Hey Jorge, so that's what I've done. However because I've done that the curve no longer creates a perfect circle, right? Like if you take a hexagon and add a subdivide to the two top edges, then, when you apply a sub surf modifier to the circle it looks like an egg, not a circle. I'm trying to fix that weird warp that takes place. $\endgroup$ Jan 23, 2019 at 15:30
  • $\begingroup$ That's the part I don't get it, if you subdivide your entire circle adding sub surf won't any issue, could you share your model please? $\endgroup$ Jan 23, 2019 at 15:58
  • $\begingroup$ Hey Jorge, I added more images to help discuss. I show the hexagons and the problems created when subdividing as I'm doing to create the additional edges needed for extrusion. I found subdivide smooth works if you do it on all edges but doesn't work if just on a specific few. Also, really what I want to do is a loop cut because it allows me to position the vertices where I want them positioned but it functions the same as a subdivision if I don't choose to move it which creates the problem. $\endgroup$ Jan 23, 2019 at 16:35

There are two possible reasons for Catmull-Clark not approximating a circle well. (BTW, being cubic, subdivision will never exactly produce a circle)

  1. The points to be subdivided do not lie on a circle
  2. They do, but they are are not spaced evenly on the circumference.

The Loop Tools add-on addresses both, with its 'Circle' and 'Space'options.

There still needs to be a bit of forward planning with vertex counts,so these tools don't distort faces too badly


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