There are two parts that I want to combine, but when switching to the subdivisions surface modifier, a square joint is formed.

On one side and on the other, there were a different number of edges, which is why some of them had to be dissolved and the edge was drawn into quadrilaterals. I also tried to convert these borders to a circle, and the joint itself, too, but nothing works.

The most interesting thing is that with the other two parts, everything went perfectly, there was no such problem.enter image description here

(this is my very first experience just straight after donut, pls be kind <3)

  • 2
    $\begingroup$ Hello, you probably have some inner faces or please share your file $\endgroup$
    – moonboots
    Apr 14 at 8:34
  • $\begingroup$ Hello, thanks for your answer, when i saw it for first time i thought the same, but there no inner faces. also idk how to share it here :) i would be really thankful for any help $\endgroup$
    – Eri
    Apr 14 at 8:42
  • $\begingroup$ Hello, Eri, follow the instructions on blend-exchange.com, and paste the resulting link into your post.. try A select all, M > Merge By Distance ? $\endgroup$
    – Robin Betts
    Apr 14 at 8:54
  • $\begingroup$ "Straight after donut"... a reference only Blenderheads understand. ;-) Nice. (Welcome to the site!) $\endgroup$
    – Mentalist
    Apr 15 at 1:12
  • 1
    $\begingroup$ @Mentalist Thanks, I appreciate that <3 Before searching tutorials on youtube i was curios why there are so many different and even more identical donuts on the first search site for download 3d model, then I understood :D $\endgroup$
    – Eri
    Apr 15 at 10:02

1 Answer 1


As you can see you have flipped normals, select all in Edit mode and press ShiftN:

enter image description here

  • $\begingroup$ YAAAYYYYY!!! NOW I SEE Thank you so much <333 $\endgroup$
    – Eri
    Apr 14 at 9:37
  • $\begingroup$ @Eri Please accept the answer if this is the solution. $\endgroup$ Apr 14 at 20:20
  • $\begingroup$ @GordonBrinkmann thanks, i didnt notice this function, just accepted $\endgroup$
    – Eri
    Apr 15 at 8:56

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