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I made a circular window along a curved surface with Subdivision Surface modifier applied.[![enter image description here][1]][1]

The bottom edge seems fine, however the top edge is crimped and somewhat distorted, the top edge also forms a lip which projects away from the mesh and is visible when in front view;

and here is the underlying geometry, which as far as I can tell is all quadsenter image description here

How do I retopologise to fix this, if that is at all possible? How do I avoid this problem in the future?

Update: The topology shown here has been modified in that I deleted the quad faces around the circle. However I still don't know how to connect the circle to the outer edge loop smoothly. .blend:

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  • $\begingroup$ Topology looks good, it is the density that seems a bit off. The circle looks "twisted" in relation to surrounding loops. Try rotating it a bit around its center. An additional edge loop around the circle may also help. $\endgroup$ – Duarte Farrajota Ramos Sep 10 '17 at 16:32
  • $\begingroup$ Adding an additional edge loop has no effect unless it is brought right on top of the circle or on top of the surrounding edge loop,in which case it amplifies the distortion on both edges. Similarly, rotating the circle around it center shifts the lip" to the bottom edge,but the top edge is still noticeably crimped. $\endgroup$ – K. Ra Sep 10 '17 at 17:01
  • $\begingroup$ Is it worth noting that the crimping follows exactly the edges which connect the circle to the corners on the top and bottom? $\endgroup$ – K. Ra Sep 10 '17 at 17:02
  • $\begingroup$ Why not just do it manually? $\endgroup$ – SilverRain Sep 10 '17 at 18:06
  • $\begingroup$ Every attempt I've made at at retopologizing so far has encountered the same issue of pinching/crimping. Im not sure how to go about it while preserving the circular profile of the window, avoiding pinching of the model and avoiding Tris/Ngons. $\endgroup$ – K. Ra Sep 10 '17 at 18:46
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I believe it's an issue with the density.

enter image description here

What you might want to do is start over and equal out the densities of Yellow and Red (several ways to approach this) before punching the holes to get an easier and cleaner result.

Alternatively you could add another ring and then retopo accordingly to get a cleaner hole.

Here's a quick example (sorry for the messy image).

enter image description here

I used bevel on the outer ring to add another ring.

Next time, please link the mesh so it's easier for us to help you :D

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  • $\begingroup$ Thank you very much for this answer, it looks like it would work, but is a little bit over my head in that I not familiar with "density" and how to equalize it across a mesh, and tutorials I could find addressing it aren't very helpful. I would be grateful if you could elaborate once I upload a .blend file, which will be very soon(I've had to start over) $\endgroup$ – K. Ra Sep 13 '17 at 4:57
  • $\begingroup$ Sure bud, link the .blend at blend-exchange.giantcowfilms.com $\endgroup$ – Jun Sep 13 '17 at 18:25
  • $\begingroup$ Please excuse my late reply, I've been having serious issues which made it almost impossible to use my computer, or to operate the right click function. I have just sorted that out. I sincerely hope you didn't wast time waiting for my reply. I will link the mesh in the .blend in the comments and in the original post. $\endgroup$ – K. Ra Sep 19 '17 at 21:21
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In your case, probably the easiest thing to do is this:

  • Delete the inner circle.
  • Select the outer rectangle, and then extrude and scale it down (ES 0.7 or so).
  • Use To Sphere (⇧ Shift⌥ AltS) > 1 to turn the rectangle into a circle.

End result on a cube:

inset-circle

Edit: Didn't see that it's on a curved surface. This may not work very well; you should try rotating the existing circle first.

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