3d printing question

So I’ve seen different answers on this question, so thought I would ask here. I’m making a model for 3d printing. But after spending a few hours sculpting, I say many people say your model has to be one uniform mesh. No multi part meshes. But then others say it can be made of different parts. So which is it? It seems to be very hard to make a uniform mesh if you’re sculpting.

What I’m working on is a 2x2 dungeon tile. I made the base a single model and then each stone tile is a separate mesh I’m sculpting. It would be very hard to merge these together.

Here is an image of the idea I’m going for. Please note this is not my model, just the same idea. In their model, the wall clearly looks like a separate mesh from the floor to me. Also the model is one model, they didn’t print it as 2 pieces and glue them together.


A few thoughts. First, the print in your picture is probably two parts, but it was probably printed as two parts and then snapped/glued together.

A file for 3d printing can have multiple separate (and fully closed) meshes, but they can’t overlap. So you could have two bricks next to each other and it would print as 2 disconnected bricks. But you couldn’t make a simple wall shape and have separate brick meshes sticking into it.

At the same time, it’s less important to have neat topology for a 3d print. In fact .stl files used for printing usually have garbage topology when imported into blender. So if you can get your meshes to boolean together, it doesn’t matter if you have bad edge flow or etc.

Thank you for the reply. Ok the wall in the pic. How would have they made that? A single wall mesh with the brick faces extruded out and then the forward faces are sculpted? My biggest problem would be the boolean with a sculpt. The floor tiles are sculpts with thousand and thousand or faces while the bases is not. Wouldn’t that be a big problem to boolean them together?

I was really into sculpting up some RPG tiles, but after finding out your mesh can’t go through another mesh, it’s killed my enthusiasm. Over half the things I had planned would be impossible to make now.

Ok here is a 3d printed model. It looks like it has sculpted stones. Now a lot of this looks like separate parts when it was made. Like the flags, shield, arch stones. So would he have boolean that all together? This seems like a huge problem for 3d printing. It should be based on outside image surface, not what’s inside a mesh.

So maybe the workflow would be create everything as different meshes, sculpt what needs sculpting, boolean and decimate? If so, decimate before or after boolean?


Well, that’s definitely a render. But it is a firm requirement for 3d printing that it be one manifold mesh. In some cases a printer’s slicing software will handle overlapping geometry but it’s much better to avoid it. Check out this basic tutorial on creating files for Shapeways printing: http://www.shapeways.com/tutorials/prepping_blender_files_for_3d_printing

What you say “It should be based on outside image surface, not what’s inside a mesh,” that’s exactly how it does work. But the geometry has to be set up so the software knows what the outside surface is. If you have faces that start outside but then go inside…it can’t tell. Any slicing software that works around this is essentially doing a boolean behind the scenes to create a closed volume. Better to do it yourself so you have control.

For creating new geometry, it’s not that it’s impossible to create; you just have to start from different assumptions than if you’re creating models for rendering. I would guess the arch above was either scanned from a physical sculpture, or done almost entirely in 3d sculpting rather than vertex modeling. For instance in zbrush (or blender) it would be possible to set up a “stone brick” sculpting brush to make the textures easily.

The parts you mention looking like separate geometry were probably modeled that way, and then merged. If you look closely at the corners around the arch stones, you can see where it blends softly into the wall. Blender will do this decently, but you can use something like meshmixer as well.

As an example, take a look at these dungeon wall tiles on Thingiverse. Download one of the STLs and open it in blender, you will see that the bricks are merged with the back wall rather than clipping through. From the clean nature of the rectangular base mesh, I’m almost certain that they sculpted the bricks, then booleaned them with the simple rectangular frame. When you don’t care about final topology, boolean isn’t as scary as when you need neat quads in the end.

Ok I see now. I think my main problem is I’m think of this from a normal blender user and not a 3d printing user. Which is why I was so worried about the boolean. I would normally never use that for sculpts like that. Thanks a lot for your answers. One finally question, what is the highest level you think multires should go? Right now I’m doing 5. But since these are so small, is that too high or more? Because stones have those big cracks which is hard to do at low levels.

Depends on the size and resolution you’re going to be printing, really. Many consumer 3d printers don’t go below .1mm layers. So any details smaller than that won’t show up. You have to think about the “real” size of your model and generate details appropriate to that scale.

I would suggest using dynamic topology in sculpt mode rather than multires - that way your big flat areas can stay as such but you can add as much detail as you need in the more complex areas. That lets you save triangles for areas where you need them for detail. For reference, one of the 3x3 wall tiles I linked to above has about 500k triangles.

I do a lot of Blender modelling for 3d print. Some tips to make things easier, especially when using booleans to create a single mesh.

Be mindful of the subsurf levels when combining objects with booleans. You can very easily end up with very dense parts of your mesh that make it difficult to add additional modifiers after they are joined. Of course you need density where there is more detail, but when using booleans, it is very easy to get accidental density where you don’t want it.

If your booleans don’t work, this is usually due to 1) duplicate vertices, 2) inverted normals 3) not applying scale and rotation or 4) intersecting triangles. It is much easier to deal with these things before you use booleans. If not, even if the boolean works, you may end up with internal geometry and non-manifold edges that are a pain to clean up afterwards.

Use crease weights to keep edges crisp and a final subsurf when exporting the model. There is no need to apply the modifier before exporting. This gives you control over the final model size in case your slicing software complains that your file size is too big.

I agree with spiderbrigade that you should keep the real-world scale in-mind during sculpting. My printer had a nozzle size of 0.4mm and a minimum layer height of 0.1mm. Any detail you add that is smaller that that is wasted. If you plan on using any of the online printing services, you will need to think about creating hollow models to save on material costs, and adhere to minimum and maximum wall thicknesses. I often make some appropriately sized cubes alongside my model as a rough visual guide to real-world sizes.

Good luck, I would like to see what you ended up with.