FBX export of armature changes rest pose if without weighted mesh #113073

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opened 2023-09-30 02:09:26 +02:00 by Jer Bot · 5 comments

Jer Bot commented

2023-09-30 02:09:26 +02:00

Operating system: Windows
Graphics card: nVidia

Tested in version 3.61

If exporting a keyed Armature skeleton without a bound/weighted mesh, the rest pose will be changed to whatever the current pose is on the current frame.

To recreate issue:

Part 1
Create an armature (a single bone is fine)
Enter pose mode and pose the bone(s).
Export "selected" to FBX using otherwise default settings.
...
Part 2
In a new blender file, import the exported FBX file.
Try to reset the bone(s) to their rest pose (Alt+R, Alt+T, Alt+S).
Notice how the bone keeps the pose.
...
Now try the same steps, except in Step 2 use an Armature Modifier to bind a Cube to be deformed by the Armature, and then export both the Armature and the Cube.
Notice how the imported Armature maintains can be brought back to its original rest pose.

Expected Results
I would not expect the rest pose to be altered when exporting a posed bone.
If the Armature is keyed, the rest pose will be generated from whatever the pose happens to be on the current frame, meaning that exports will differ depending what frame is being displayed.

Operating system: Windows Graphics card: nVidia Tested in version 3.61 If exporting a keyed Armature skeleton without a bound/weighted mesh, the rest pose will be changed to whatever the current pose is on the current frame. **To recreate issue:** Part 1 Create an armature (a single bone is fine) Enter pose mode and pose the bone(s). Export "selected" to FBX using otherwise default settings. ... Part 2 In a new blender file, import the exported FBX file. Try to reset the bone(s) to their rest pose (Alt+R, Alt+T, Alt+S). Notice how the bone keeps the pose. ... Now try the same steps, except in Step 2 use an Armature Modifier to bind a Cube to be deformed by the Armature, and then export both the Armature and the Cube. Notice how the imported Armature maintains can be brought back to its original rest pose. **Expected Results** I would not expect the rest pose to be altered when exporting a posed bone. If the Armature is keyed, the rest pose will be generated from whatever the pose happens to be on the current frame, meaning that exports will differ depending what frame is being displayed.

Jer Bot added the

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Pratik Borhade commented

2023-09-30 05:08:49 +02:00

Member

Hi, thanks for the report. I can confirm. But this seems a bug with fbx I/O which should be reported at: https://projects.blender.org/blender/blender-addons/issues

Hi, thanks for the report. I can confirm. But this seems a bug with fbx I/O which should be reported at: https://projects.blender.org/blender/blender-addons/issues

Pratik Borhade added

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Thomas Barlow commented

2023-09-30 13:59:06 +02:00

Member

I think this may be an FBX limitation. The FBX IO addon exports Bind Poses, but these include the mesh(es) and the bones that deform the mesh(es) (and their parent bones). No meshes exported means no Bind Poses are exported.

The FBX SDK documentation does mention Rest Poses, but I'm yet to see one in an actual file, so I don't know if the FBX IO addon's importer will do anything with them, nor what sort of support other software has for them.

I think this may be an FBX limitation. The FBX IO addon exports Bind Poses, but these include the mesh(es) and the bones that deform the mesh(es) (and their parent bones). No meshes exported means no Bind Poses are exported. The FBX SDK documentation does mention Rest Poses, but I'm yet to see one in an actual file, so I don't know if the FBX IO addon's importer will do anything with them, nor what sort of support other software has for them.

Jer Bot commented

2023-10-04 01:44:51 +02:00

Author

@Mysteryem & @PratikPB2123

Thank you (both) for verifying this. I also have a feeling that this is the case (inability of FBX to store rest/bind pose without mesh).
It does seem related to this: blender/blender-addons#85496

How can I move this case or should I just copy / paste it over?

@Mysteryem & @PratikPB2123 Thank you (both) for verifying this. I also have a feeling that this is the case (inability of FBX to store rest/bind pose without mesh). It does seem related to this: https://projects.blender.org/blender/blender-addons/issues/85496 How can I move this case or should I just copy / paste it over?

Pratik Borhade referenced this issue from blender/blender-addons

2023-10-04 11:24:13 +02:00

FBX export of armature changes rest pose if without weighted mesh #104937

Pratik Borhade commented

2023-10-04 11:25:00 +02:00

Member

Unfortunately, there is no easy way to move reports between repository. You'll need to create a fresh report in add-ons repo 😅
Anyways, created a fresh report: blender/blender-addons#104937

Unfortunately, there is no easy way to move reports between repository. You'll need to create a fresh report in add-ons repo 😅 Anyways, created a fresh report: https://projects.blender.org/blender/blender-addons/issues/104937

Pratik Borhade closed this issue

2023-10-04 11:25:03 +02:00

Blender Bot added

and removed

labels 2023-10-04 11:25:06 +02:00

Jer Bot commented

2023-10-05 03:21:03 +02:00

Author

@PratikPB2123 No problem. I would have been happy to do so... but, THANK YOU for doing that. 👍

@PratikPB2123 No problem. I would have been happy to do so... but, THANK YOU for doing that. 👍

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