I need to add holes for some connectors to my mesh. But, Boolean modifier messes up the mesh, as does bool tools. I have looked at several youtube vids but haven't seen one yet that can make a hole like this without screwing up the topology.

Here is what I am trying to model.

Here is what happens with Boolean modifier: enter image description here

And here is the mesh after

Here is the blend file:

  • 2
    $\begingroup$ the @Andres Aguilar answer below imho points to the cause: n-gons created by booleans. Due to the complex shape, I would try to keep those holes, and after applying boolean, rebuild geometry around them, until they are all quads... I mean all of the resulting shape... $\endgroup$ – m.ardito Sep 13 '17 at 16:15

You'll want to use custom normals. Blender has a data transfer modifier which allows you, among many other things, to copy normals from one mesh to another.


  1. Keep your untouched mesh as the source for the normals and make a copy of it.

  2. For the copy, add the boolean modifier or whatever you want to use to cut it.

  3. On the copy, in the Data Tab, turn on Auto Smooth and click Add Custom Split Normals Data. We do that to allow the use of custom normals.

  4. Add a Data Transfer modifier to the copy. Set the untouched source as the modifiers' Source Object. Turn on face corner data, and in the dropdown menu right to that, select Projected Face Interpolated.

  5. Finally you can apply the data transfer modifier and delete the normals' source model.

  • $\begingroup$ This technique is cool! The mesh looked better almost from the moment I added the Data Transfer modifier. However, I think I still need to go in and add some verts so that I can bevel the edges of the circles properly. Although... I think I have a way around that. More testing to do! Love this forum! $\endgroup$ – Matt McKee Sep 13 '17 at 18:23

Its because you are working with N-gons there as Boolean operation doesn't care about your model topology.

The best solution for you seems to be as easy as make a new Circle, join it to your mesh, and manually join points so you get less distortion in your mesh.

Also, you can use a flat sahding technique on the flat areas and keep using smooth shading on the most vertex poblated ones.

  • $\begingroup$ This one is another attempt I was going for but ran into problems bc the surface where I was attempting the two closest holes is curved. I never did figure out the order for the knife project tool. I will give that a try next. I was just hoping not to have to do a couple of hours of connecting verts. Sigh. $\endgroup$ – Matt McKee Sep 13 '17 at 18:20

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