Help 3D-Printing "People Parts"

[jcolag]

Hi, I'm new to a lot of 3D work and the forums, but have worked on a lot of other things for a long time, so first, if I cross a line or say something that doesn't make sense, please do me the favor of nudging me in a better direction. I haven't used it for anything, but I've followed Makehuman for at least fifteen years, and as a bystander, it's made me excited to see the improvements.

Introductory stuff out of the way, I've searched the forum and found vaguely similar questions, but either my specifics differ too much or I completely lack a grasp of the software involved, so...help! Long story short, I'd like help finding some way (preferably with open source software) to get the object that represents the solid volume inside the character mesh. Apologies for the length from here, because I want to make sure that I clarify my needs instead of my informal terminology leading everybody in the wrong direction.

As background, I'm close to launching a (hopefully community-involved) open source story, and had the semi-goofy idea of releasing DIY toys alongside the installments. I created some robotic action figure prototypes using OpenSCAD that pleased me, and now it's time for people instead of clunky 1950s-looking robots. I pull the latest version of Makehuman and create the first character.

Two paths, here, both seemingly leading to the same end. Either I export the character as an STL file or use the Makehuman Blender add-on to import the character there and export to STL from there after using the 3D Print Toolbox add-on mentioned in an older post on a similar topic, to find and clean up the non-manifold edges and so forth. In either case, I pull this into OpenSCAD so that I can start pulling the body apart to create the parts to a poseable action figure, but I only ever seem to get a surface mesh (where random bits become transparent on the first intersection or difference operation), whereas I need a (physically) solid object (like an OpenSCAD cube), where I can apply intersections, differences, and unions to pull out the pieces that I want, only hollow out the parts that need it, and attach pegs and the like for assembly.

Unfortunately, searching for this sort of thing on the broader Internet will tell me all sorts of ways to "fill the mesh" (probably necessary in the process, but nothing like the end goal) or "solidifying" the mesh in the sense of hanging voxels along the outside to create an approximate shell. One suggestion led me to create an empty volume and use an object-to-mesh modifier on it in hopes of fitting the volume to the shape, but that only gave me either a vague cloud around the head and chest of the character or (if I increase the number of voxels to the point where the cloud starts to fill the shape) a computer crash. In the case where the computer survives the ordeal, the cloud doesn't even export to show up in OpenSCAD.

I tried similar things in FreeCAD that I did in Blender, by the way, but it didn't improve the situation. Oh, and I started looking at the STL specification to see if I could write code to generate the equivalent volume, but got lost in the details when it didn't look straightforward.

As such, if anybody has a process where I can get a solid volume that fits the interior of the Makehuman mesh, I'd be very grateful. (If it's a better question for some other software's community, I apologize, but I assume that people here have more familiarity working with the meshes themselves.)

[tomcat]

Long story short, I'd like help finding some way (preferably with open source software) to get the object that represents the solid volume inside the character mesh.

I am just beginning to explore this area. But as far as I understand the question (if I understood it correctly), the filling is done in a slicer (3D printing program) [Slic3r]. You need to get a whole (complete, solid) part of the model (body) — the 3D printer does the rest.

Do you have a sample of what you want to get? What is the total size of the figure and its parts?

[jcolag]

I am just beginning to explore this area. But as far as I understand the question (if I understood it correctly), the filling is done in a slicer (3D printing program) [Slic3r]. You need to get a whole (complete, solid) part of the model (body) — the 3D printer does the rest.

So, I think (from what little I know about 3D printing in general) that might work for a single object, but the added wrinkle is that I want to "disassemble" the person to, for example, attach the arms to the torso by a rotating peg. That seems to require having a model that software understands as "solid," so that I can divide the model into the relevant pieces.

Do you have a sample of what you want to get? What is the total size of the figure and its parts?

It depends on what you mean. I imagine that any "human" will work as the starting point, since the specifics won't matter, but if you're familiar with OpenSCAD, I have the (1950s-looking robot) on Codeberg https://codeberg.org/jcolag/lights-edge ... lll-1.scad (and change ".scad" to "stl" for the export.) In the same way that I hollow out and run holes through the big cylinder, I'd like to do something similar with a character's torso, if that makes more sense.

[tomcat]

So, I think (from what little I know about 3D printing in general) that might work for a single object, but the added wrinkle is that I want to "disassemble" the person to, for example, attach the arms to the torso by a rotating peg. That seems to require having a model that software understands as "solid," so that I can divide the model into the relevant pieces.

I'm using a translator and so I may not quite understand. But in general, yeah, composite and moving models are made in separate parts and assembled after printing.

And the “disassembly” of the model into component parts is done in the modeling program (Blender). And the joints (connections) of the parts are also formed there.

It depends on what you mean. I imagine that any "human" will work as the starting point, since the specifics won't matter, but if you're familiar with OpenSCAD, I have the (1950s-looking robot) on Codeberg https://codeberg.org/jcolag/lights-edge ... lll-1.scad (and change ".scad" to "stl" for the export.) In the same way that I hollow out and run holes through the big cylinder, I'd like to do something similar with a character's torso, if that makes more sense.

Can I ask what the end goal is? A picture of what you are aiming for would be enough for me.