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Here's a screen recording of me trying to create the intersection

I'm hoping clip the terrain block mesh to the border map for 3d printing, but the result is missing all but the southern side. I've recalculated the normals and verified both meshes.

I'm not sure why it's happening here, but if there's another way to fill the side holes despite the complex shape, that would work too.

Here's the blender file if it helps (only the meshes near the origin are relevant)

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  • $\begingroup$ That's quite a large blend file! $\endgroup$
    – Moog
    Commented Oct 20, 2019 at 15:12

2 Answers 2

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Recalculating your normals isn't enough to get proper normals if you don't have manifold geometry. Here, by enabling face orientation in overlays, we can see that many of your normals are facing the wrong way:

enter image description here

When we start fiddling with the vertices to figure out why these sections have backwards facing normals, we find strangely ripped edges, ripped only partially:

enter image description here

If we perform a select non manifold operation, we can see that huge portions of your mesh get selected. However, if we limit that selection to vertices that are non-manifold due to multiple faces, there are no problems. That's a good sign: it means that your mesh issues can probably be solved by merging by distance. So we'll select all vertices, merge, then recalculate normals.

This won't always work. Sometimes, merging will create non-manifold geometry. Here, after the fix, we can again use select non manifold (with all criteria enabled) to look for problems, and discover there are none.

Now we'll see our boolean intersection working perfectly, even with the fast solver (which I believe was all that existed in 2019):

enter image description here

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I have similar issues with blender 2.8 boolean modifier, but "fast carve" free add_on works fine so far. It could be a glitch in controls / settings for me, not sure anyone will have another answer unless your file is wrong some how.

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  • $\begingroup$ Is there a good way of looking for issues with the file? I'm a bit of a noob and I got the terrain mesh from an online generator. $\endgroup$ Commented Oct 20, 2019 at 14:51

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