A continuation of a previous post . I'm looking to cut a rectangle into an arc that i've modeled but running into some topology problems that I couldn't resolve. Below is an image of what i'm trying to do: Test 1

I've tried a couple of methods (that I know so far to my knowledge)

  1. creating a mesh that has the inset and then extruding it after --> problem by doing this is that i'm unable to straighten the edges of the inset, they end up just being curves. For this, i've tried using subsurf edge (SHIFT + E) Curved edges around the inset

  2. Another method i've tried is doing a boolean but that just completely messes with the entire model...

Reaching out to the blender community and hoping someone may have an answer to this!

  • $\begingroup$ Can u share your .blend file? $\endgroup$
    – Nxdhin
    Aug 28, 2020 at 4:31
  • $\begingroup$ The curves you don't want.. are they the small bevels in the corners of the inset? Is this for visualisation or printing/cutting? $\endgroup$
    – Robin Betts
    Aug 28, 2020 at 7:40
  • $\begingroup$ @Nxdhin2005 Here's the file! we.tl/t-iGyBG6uC1P A bit more context, the first two curves starting from the left are my back and front pieces. The third curve is my attempt at creating the rectangle shape in the mesh itself before adding any modifiers. The fourth curve was my boolean attempt and the fifth curve is just the original mesh $\endgroup$
    – Otochi
    Aug 28, 2020 at 14:58
  • $\begingroup$ @RobinBetts I'm not sure if they're bevels or not but maybe something of that sort where i just need to sharpen the edge or something? And this is for 3D printing! $\endgroup$
    – Otochi
    Aug 28, 2020 at 14:59
  • $\begingroup$ @Otochi you can add the blend file to the question using the edit button to edit your questions to add more details into it. ; ) $\endgroup$
    – Nxdhin
    Aug 28, 2020 at 17:19

1 Answer 1


The basic key to a good subdivision surface result is having a loop of faces along either side of any edge that you want to harden. In your case, you have supporting edge loops on the extruded sides of your arch, but not on the large flat surfaces:

enter image description here

I used the bevel tool with the following settings to create face loops around each of the edges that needed to be hardened. This could also be done with the bevel modifier, using either angle or bevel weight as the control.

enter image description here

Here is the result with subdivision. Note that because the top and bottom are completely flat, and surrounded by face loops of quads, it doesn't matter that much that the geometry as a mess, as long as none of the n-gons are too concave. They can even be made all tris:

enter image description here

  • $\begingroup$ thank you so much! I tried out the bevel and readjusted the rectangle cut out in the mesh and it worked! One question in terms of the geometry in the example you showed above. Did you just randomly select vertices (in multiples of 3) to create to faces? $\endgroup$
    – Otochi
    Aug 29, 2020 at 4:30
  • $\begingroup$ Yeah, pretty much at random. I could have turned all of those inner n-gons to Tris. As long as you don't have and large concave faces $\endgroup$
    – Rekov
    Aug 29, 2020 at 6:01

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