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(Probably not the best title for this issue but I've no idea what to write instead)

I have this model

Before extrude

And I want to extrude the selected area along Z by -0.1. When I do that I end up with this

After extrude

As you can see I get a "fence" along the outer edge of the model, which I don't want. I tried ticking "Disolve orthognoal edges", and that is why the fence is missing one face.

I understand why the extrude command does this, but I can't figure out how to do it properly, and preferably fast (since I have to do a lot of these hexes). Deleting the fences' vertices screws up the remaining geometry, so fixing it after the extrude command is not straight forward, at least not for a newbie like me.

Any and all pointers would be appreciated.

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    $\begingroup$ if extrude manifold doesn't work, maybe do the opposite (extrude upwards the other part, then lower down the whole top?) $\endgroup$
    – moonboots
    Commented Oct 25, 2021 at 8:14
  • $\begingroup$ Yes that is second possible solution in my mind as well, but it still depends on what exactly he needs, this solution would remove the bad topology, try both and see which one is faster for you $\endgroup$
    – MikoCG
    Commented Oct 25, 2021 at 8:15

1 Answer 1

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Try to use Manifold extrude: enter image description here

You will find this either by holding Alt+E and selecting manifold, or by changing default extrude to manifold in your tools by holding it: enter image description here

Your topology will be still wrong as it will create ngons (technically, but it really depends on if you really need topology to be right or not)

Okay, after reviewing your file, this is the problem: enter image description here

This happens for a simple reason, the reason is that your face on that side has 5 vertices and not 4.. that's all, look what happens when I cut it with a knife into 2: enter image description here

And it suddenly works when you add a line in the red spot, this is due to you should always make your topology as clean as possible, in your case you need to remove faces with 5 vertices and make 2 with 4 vertices. Always try to go for quads.

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  • $\begingroup$ I tried it, but it left a small piece of fence intact. Extruding the higher part up first then moving all the top vertices down again as the other commenter suggested did the trick. Not sure why it worked so well for you in the above picture but not for me $\endgroup$
    – westmark
    Commented Oct 25, 2021 at 8:26
  • $\begingroup$ maybe share your file so that we can give a try: pasteall.org/blend $\endgroup$
    – moonboots
    Commented Oct 25, 2021 at 8:41
  • $\begingroup$ You guys are super-helpful! pasteall.org/blend/d98d2c6a9b55457cb4d2107e1284e9ef $\endgroup$
    – westmark
    Commented Oct 25, 2021 at 9:54
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    $\begingroup$ I just looked at it and I know why it is happening, your topology has 1 mistake, let me show in my answer, I will edit it in a second,... edited $\endgroup$
    – MikoCG
    Commented Oct 25, 2021 at 10:10
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    $\begingroup$ No, I used knife on original model, I just didn't include it in photos $\endgroup$
    – MikoCG
    Commented Oct 25, 2021 at 11:15

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