Boolean

[maxcady]

Why the boolean modifier doesn’t work as intended sometimes? (with 2 meshes)

What are the factor that does not make a good result?

[Martin Bergwerf]

Hi @maxcady ,

Non-manifold Meshes (not ‘watertight’; having (a) hole(s), having Edges that connect to more than 2 Faces…) can create problems with Booleans.

Although the Exact Solver has some options to get better results with those situations, correct behavior is even then not guaranteed.

Inconsistent Normals are really bad!

[Omar Domenech]

Yeah as Martin says. There are certain topology rules to have in mind, but also coding for booleans is probably hard and they don’t always work as intended.  When booleans misbehave what I always do is move the object around a bit and more often than not things re-adjust and it all works.

[maxcady]

Where can I activate the exact solver?

I have a addon that comes with Blender that can say how many manifold there is on a mesh. For example: This mesh has 32 non manifold edges.

This mesh

Is it goos and do I have to make it all manifold??

[Omar Domenech]

Looks good. Those 32 are because of the hole up top. if you select the loop of vertices you see there are exactly 32. You can make booleans in that mesh for sure. What’s the name of that addon that checks your mesh?

[Martin Bergwerf]

The 3D-Print Toolbox Addon (comes with Blender) checks Meshes:

…and has a Make Manifold button.

[maxcady]

thx. Just add it. Didnt notice there is a manifold button. So is non manifold good or bad?

[Omar Domenech]

I’d say neither. It depends on your situation, if you’re doing a model for games, for 3D print, for a movie production, for personal use, for sale, etc.

[maxcady]

yeah but I mean, to unwrap and add textures?

[Martin Bergwerf]

Non-manifold is either harmless or bad in 3D computer graphics, depending on the situation.

Subsurface Scattering and Volume Shaders don’t like holes, for instance.

Booleans can give incorrect results.

The Dual Mesh Node (in Geometry Nodes) only works on manifold Meshes.

3D printing doesn’t do non-manifold Meshes.

But it’s not always bad; a Plane is also non-manifold!

[Martin Bergwerf]

No problems for Unwrapping and adding Textures.

[maxcady]

Experience will help me with time.

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