Bolt Nut Sculpture for Blender 4.1

This tool gives your mesh the appearance of having been made out of bolt nuts. It works by turning your mesh surface into a vaguely honeycomb grid, and instancing a nut onto each face, sized relative to the respective face area.

The key to this is good topology, which in this case means that if the mesh is constructed predominantly from quads then those quads are approximately square, and if triangles then those triangles are approximately equilateral.

To illustrate the point, I've included an image that shows two versions of a horse's leg, the one on the left having the better topology for our purposes.

There are various tools for doing this, including in-house tools, 3rd party add-ons, and external apps; I like Instant Meshes, which is a free, standalone app which can import and export .obj files.

Once you have a decent mesh, you can bring it into Blender and attach this Geometry Nodes modifier.

Because the maths is crude (really not my forte), and the hexagons are often quite irregular, some global adjustment will be required to get the nuts to the right size. I've presently included controls on the Modifier panel for the following:

- Size Tweaking (as described above)

- Alignment switch - in some cases (particularly noticeable with icospheres), enabling this will align the nuts better with their underlying hexagons. Usually, it will make things worse, but it's there if you want to try it.

- Subdivision - Essentially whether you have 1, 9, 49, 225, or 961 hexagons for every 4 quads! The default is zero for a reason. Use with caution, and save before use, as increasing subdivisions is very likely to crash Blender!

- Noise - This adds a bit of irregularity to the mesh surface, and deletes a few faces in the process.

- Vertex Group Deletion - if a vertex group is submitted, then these points (and surrounding faces) will be removed from the resulting geometry. In the visual below, a small portion of the horse's belly is removed in this way.

- Random face deletion - because these sorts of models often have largish gaps in their surface, I've included a tool to emulate this. Use sparingly because of, you know, gravity.

These are just a couple of ways of deleting faces; there are dozens of others , including using textures, normals, and vector position.

Finally, there's a 'Rustiness' attribute, which offers some simple, limited texturing control.

As I say, this is a fairly crude implementation of this effect. Better methods might use python scripting and/or differential growth, to create a more plausible, even build-able, simulation.

Prerequisites:

• Requires Blender 4.1+ (only tested on 4.1). Won't work on older versions (although I'm not sure why).
• Some form of retopology software and/or workflow, for best results