Can't read some OBJ files

Bambu Lab Software
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Apparently it’s supposed load OBJ, as .obj is listed in the supported formats on import?

These ones, however, don’t work. They do work in Chitubox (a resin slicer) probably as they were designed for resin printing. And of course Blender loads them.

Not sure if I should file a bug with Bambu, of it’s downstream in Prusa etc?

I’\ve contacted the file vendor to see if their license permits me to provide the file in this case.

edit To be more clear, bambu slicer will not open the OBJ file. Chitubox and Bender will.

edit Update Prusa and Cura also do not open the file. Lychee does. So these obj files only seem to open in resin slicers.

edit Update loading the obj file into blender and then re-exporting as obj makes it work in bambu slicer.

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If Blender loads the files, save them under a different file name from inside Blender and see if they’ll slice.

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See the edit of the OP

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As expected. :slight_smile:

If re-saving the file from within Blender didn’t fix it, it would indicate that the file is making use of a feature that Blender understands but the slicers do not. So your outcome confirms there’s a bug in the BBL slicer (as well as the others you tried). Blender “reparsed” the geometry and that made the problem go away. Except you know the geometry was OK to begin with since some slicers were able to open it.

The Resin slicers probably do a better job because they’re mostly going to be ground-up implementations from the company that made the printer (that’s the case with my Formlabs printer, for example, which uses a laser beam, so it prints in a way that is similar to what a FDM printhead does. mSLA uses a LCD panel has a completely different method for doing the full-layer-at-a-time slices). Many FDM slicers are based on the same core open source stuff.

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OBJ and STL files have vastly different features. OBJ has as an example, color and texture whereas STL do not. You might try bringing the OBJ file into blender, removing both texture and color and then reexport to an OBJ just as a thought experiment.

Here’s a side by side comparison.

Feature OBJ File STL File
File Extension .obj .stl
File Format Text-based Binary or ASCII
Geometry Representation Supports polygons (faces) Supports triangles
Colors and Textures Supports colors and textures Supports only geometry
Normal Information Supports vertex normals Supports only facet normals
Vertex Data Stores vertex coordinates Stores only vertex coordinates
Face Data Stores faces as vertices indices Stores only triangles as facets
Surface Materials Supports material definitions No built-in material support
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One thing I have noticed with OBJ files is they need to be exported in tris and not quads and then they seem to work for me. Purely anecdotal, but I was having this same issue when trying to export out of Max as an OBJ file with the export set to quads as generally, thats cleaner for me to work with and most engines convert to tris anyway on their end. I wonder if they require tris in order to generate some type of smoothing information easier for the printer. Ill continue to look at this as I just got my first printer but have been modeling for a while. Hopefully this might be able to help you. So just to be clear, when exporting as an OBJ, in the menu that comes up, change the face from quads to tris and then continue the exporting process. Hopefully this solves your issue as it did for me.

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