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Wrong orientation in exported STL files
Open, Needs Triage by DeveloperPublic


System Information
Operating system: windows 10
Graphics card: NVIDIA GeForce GTX 1060

Blender Version
Broken: (example: 2.80, edbf15d3c044, master, 2018-11-28, as found on the splash screen)
Worked: (optional)

Short description of error
The orientations in exported STL files are mostly not correct

Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).
When I export to an STL file (especially for 3D-prints) I recognized, that the orientations will not fit to the export settings. I created a simple object (STLTest1.blend

) and exported it to all possible orientations. Import again in blender shows the wrong orientations (STLTest1_xyz_uf.blend, red ones are wrong ).



Event Timeline

This comment was removed by Dirk (disk65).

In 2.80 and 2.81, I just exported the object from the STLTest1 file, imported in back, and it kept the orientation. Note that you can pick the orientation you need both in the export and import dialogs, and if you change it in the import dialog, it'll remember what you picked when you import again.

Dirk (disk65) added a comment.EditedTue, Oct 22, 1:24 PM

I mentioned the problem when exporting an object and importing it in a slicer (Cura 4.3). Wether I set Y as top or -Y as top direction there was no change in the result.
So I made the test object above, exported in all possible combinations of directions and imported all these back to blender. Ok, I did not see the possibility to change the orientation while importing so I always used the default settings: Z top, Y forward.
The result is in the STLTest1_xyz_uf.blend. Every imported model has the name of the orientation I exported it: e.g. -zu_xf (-z up, x forward).
Maybe there is also a error in the import routine because in the front view z is positiv pointing to the top, but y is negativ pointing to me or spectator. I will test this too....

But if you export with, say, "-Y" forward, and then import with "Y" forward, then naturally the orientation wouldn't match :)

Quite right ;-) But this is not the point.
Make a small test: Use my simple project and export the model that Y is top and a second time export that -Y is top, both with Z to front. Import both stl files with standard settings. You will see that Y is allways on top. This cannot be right.
If you export Y or -Y as Up with other settings for forward, the Y side of the exported object is neither on top (again imported with default settings).
Or check the orientation of the exported files with the free online stl viewer
There is a mismatch...