I am starting to experiment with 3D printing, and I have a Bambu 3D printer with automatic material switcher. The Bambu Studio software accepts STL files. If I split a model into 4 meshes, and save those as 4 separate STL files, I can assign 4 different filament colors to each of those files.

I am led to believe online that STL files can combine all 4 of those meshes. But I can't figure out how to make an STL file with multiple separate meshes in Houdini. When I use a Merge SOP on my 4 meshes and then pipe that into a ROP Geometry Output node, the resulting STL file only appears to have 1 object in the Bambu Studio slicer app. I've tried toying with Packed Primitives, but don't really understand how they work.

Has anyone done this before? Any ideas? Or am I wrong about how STL files work?

Try using .Step files or .ply
..Google about

I am led to believe online that STL files can combine all 4 of those meshes. But I can't figure out how to make an STL file with multiple separate meshes in Houdini.

On one hand you're saying combining 4 meshes then in the next wondering how to make separate meshes.

I do 3D printing but send out to print shops and don't use a 'home' type unit.

I've used .stl for the most part but also .obj

What I know about .stl is that 'you' can't store information like color attributes on/in a .stl file.

Maybe you can, I've never needed to but have noticed when working on my model that has many group and attributes that as soon as I save out to .stl all those groups and attributes automatically get stripped from the model, i.e if I import that file to view there are no longer groups/attributes.

So I don't see how you can manage to assign colors to seperate parts of a .stl file.

But like you say, you can if you assign filament colors to different designated files. That sounds like you're doing the assigning/matching on the machine side; Not the machine reading inherent information like color in the file.

When I use a Merge SOP on my 4 meshes and then pipe that into a ROP Geometry Output node, the resulting STL file only appears to have 1 object

Yes, it is one object of 4 meshes. But no information which distinguishes the 4 meshes from each other, besides the inherent information of the physical separation;

Which for some cases allows one to send off files for printing in single files that have interlocking parts/assemblies.

.OBJ files though can save out color though, so you might want to try that.

Does your printer support .obj files? and with color?

It seems like you have to research your own printer on what file type and how color information should be stored in the file to do what you want.

Aha! Thanks for the ideas. It sounds like STL is not the super advanced file format I was imagining. I will investigate PLY and OBJ options. It looks like STP is the most advanced CAD format, but I'm not seeing a ton of options for exporting that from Houdini. I'd be glad if someone could change my mind

achrist3
Aha! Thanks for the ideas. It sounds like STL is not the super advanced file format I was imagining.

Anything but. I'm old enough to know its been around since the early 1990's : )