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I have a repeated problem with beveling complex meshes using the respective modifier, even if all what I do is to combine off-the-shelf geometric primitives with off-the-shelf modifiers, without any individual vertex-level manipulations. The effect looks often like that:

enter image description here

I tried to change the bevel modifier's many options, but the effect is that either the bevel is gone completely or the glitches become even larger.

Here is a link to the model

To work around this problem, I finally replaced the second bevel with a lattice and it even gave some more control on the shape.

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You have four boolean modifiers before your last bevel modifier. Those are notorious for creating funky meshes afterward, which is what is making your last bevel modifier go nuts. It's not working on clean geometry which is causing those artifacts.

Before any bevel I would do the booleans and apply these modifiers and clean up the resulting mesh, then add bevel. Check here: Bevel unexpected result

You could removed the bevels and do that in Cycles with the Bevel Node as well, but this isn't always ideal for fine control. https://docs.blender.org/manual/en/latest/render/shader_nodes/input/bevel.html

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  • $\begingroup$ @Leander beat me to it! $\endgroup$ – crazycourier Apr 2 '20 at 18:07
  • $\begingroup$ So if it is Blender which makes the meshes funky, why no "fix the mesh" modifier, even at the cost of completely redoing the mesh? It would substantially increase the functionality and there are many mesh construction algorithms. Applying modifiers is destructive and the mesh to fix manually is huge. $\endgroup$ – scriptfoo Apr 2 '20 at 18:15
  • $\begingroup$ Every 3d program, not just Blender, will run into similar issues. There are always workarounds, each having its own pros and cons. There are many efforts to make a "fix the mesh" function and you're free to try a lot of them. Generally "fix the mesh" is referred to remesh/retopology and there are entire courses on the subject because of its importance in the 3d world. My suggestion is to fix the mesh by hand first, remove your bevel modifiers and apply the booleans. Then look at the resulting mesh, you'll notice your last boolean is not cutting correctly because of how you have it setup. $\endgroup$ – crazycourier Apr 2 '20 at 18:32
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The glitches are caused by overlapping vertices. The only solution is proper topology, supporting the bevel.

If we examine the effect of the bevel modifier on your topology, we can see the vertices are badly positioned and the bevel quickly creates overlapping faces.

overlap

Position your edges parallel to each other and assert that the edges have a minimum length. (In your file I had to apply previous modifiers.)

better topology

When you enable the Clamp option in the bevel modifier, the bevel modifier will determine how much it can bevel before vertices/edges overlap. However, if there are dense parts in your mesh this value will be very small and result in a tiny amount of bevel. This question shows that a solution would be to split the mesh into different parts, or use bevel weights in that case.

If you model geometry, especially using n-gons, be wary of the spacing of the edges and the topology. If you add a support loop (simply inset and scale), the first bevel modifier will work fine.

topology

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  • $\begingroup$ What I did was to combine off-the-shelf simple shapes with off-the-shelf modifiers. Why are the vertices badly positioned? Wasn't it Blender which dit it? Can it be corrected without applying the modifiers? $\endgroup$ – scriptfoo Apr 2 '20 at 18:06
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    $\begingroup$ Sure, there are modifiers like Remesh or Decimate. You can take a look at my added example to see how you could change the topology for the first bevel modifier. $\endgroup$ – Leander Apr 2 '20 at 18:29
  • $\begingroup$ Why when I try make insets like you did, the new edges want to be perpendicular to the face border, and in effect cross one another? $\endgroup$ – scriptfoo Apr 2 '20 at 19:22
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    $\begingroup$ I'm not sure, if I can answer your questions. (1) In my topology example the "inset" (extruded & scaled) edges are planar and make no difference to the shape, but the new edges pointing to the center tell the bevel in which direction the new geometry should flow. (Don't know a name except planar, and I don't know automatic tools to generate them.) (2) I wouldn't recommend remesh/decimate for your problem, those were just the only reconstructive modifiers which I remembered. $\endgroup$ – Leander Apr 3 '20 at 7:39
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    $\begingroup$ (3) Flickering booleans are well known. If possible, move the geometry a tiny amount, or use a different topology, where no edges/vertices of the cutting and the target geometry overlap. (E.g. You could make a sphere with 37 rings instead of 36 and then there would be no vertices in the center.) $\endgroup$ – Leander Apr 3 '20 at 7:40

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