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3.1/3.2 wavefront OBJ exporter issues with exporting curves
Closed, ResolvedPublicBUG


System Information
Operating system: Windows-10-10.0.19042-SP0 64 Bits
Graphics card: GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 461.92

Blender Version
Broken: version: 3.1.2, branch: master, commit date: 2022-03-31 17:40, hash: rBcc66d1020c3b
Worked: (newest version of Blender that worked as expected)

Short description of error
[Please fill out a short description of the error here]

The WaveFront exporter does not handle curves.

Exact steps for others to reproduce the error
[Please describe the exact steps needed to reproduce the issue]
[Based on the default startup or an attached .blend file (as simple as possible)]

select a curve object. Then
File > export > wavefront obj > check curves as nurbs > export wavefront obj.
That exports an empty file.

Blender can exports curves correctly.
only 3.1 and 3.2 has this problem.

Event Timeline

Omar Emara (OmarSquircleArt) changed the task status from Needs Triage to Needs Information from User.Apr 6 2022, 10:05 AM

I can't replicate this issue on a simple Bezier curve. By an empty file, do you mean a literally empty file on the file system or just a file with no contents when imported again. If yes, can you attach that file here?

Two things:

  • If I export a Bezier curve, this will not produce an empty file, but will export a mesh
  • If I export a Nurbs curve, this will not produce an empty file, but will export a nurbs curve

Is this the behavior you are experiencing?

I was always importing obj files in Maya.
I noticed that the file was not empty.
Just Maya can not import poly and bezier type curves.

blender ver2.93blender ver3.1, ver3.2
Maya can importnurbs, polynurbs,
Omar Emara (OmarSquircleArt) changed the task status from Needs Information from User to Needs Triage.Apr 6 2022, 3:31 PM

@mill mill (mill) it would be helpful if you could attach a .blend file that shows the issue clearly, as well as indicating which export settings you have used. There are various curve/surface types possible, and various export settings, and so far it's not clear to me which combination is broken.

I atatched the blend file (ver3.1.2).

This time, exporting bezier curve crashes blender.

Yesterday it was not a problem.
I cleared the blender config files before open the file.

Maya2019 only can import nurbs curves.

Aras Pranckevicius (aras_p) renamed this task from blender 3.1 and 3.2 wavefront exporter is bloken to 3.1/3.2 wavefront OBJ exporter issues with exporting curves.Apr 7 2022, 5:54 AM
Aras Pranckevicius (aras_p) changed the task status from Needs Triage to Confirmed.
Aras Pranckevicius (aras_p) claimed this task.
Aras Pranckevicius (aras_p) changed the subtype of this task from "Report" to "Bug".

From what I can tell:

  • Blender obj exporter could never really export Bezier curves. It was always exporting them as line meshes, both with the pre-3.1 exporter and with the 3.1/3.2 exporter.
  • The 3.1/3.2 exporter does not export Poly curves at all. That's definitely a bug, I'm fixing it.
  • The 3.1/3.2 exporter crashes if within a single object you are mixing curves of different types (e.g. have a nurbs curve, and a bezier curve, both as separate segments, but in one object). That's also a bug, I'm fixing that.

I can't reproduce the crash with your attached .blend file though.

Philipp Oeser (lichtwerk) triaged this task as High priority.Apr 14 2022, 11:07 AM

Since this is partly a regression (and a bug in a new feature): will set to High prio