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Applying modifiers breaks animaiton for glTF exports
Closed, InvalidPublic

Description

System Information
Operating system: Linux [other users tested on both Windows and MacOS]
Graphics card: Nvidia GeForce GTX 980 Ti

  • We have confirmed the issue is not system specific

Blender Version
Broken: 2.80 stable

  • Also tested with some 2.81 daily builds

Short description of error
Most or possibly all modifiers seem to break animation export output for glTF models.

Exact steps for others to reproduce the error

  1. Create a model that has modifiers applied to it, such as Mirror or Bevel
  2. Add animation
  3. Export to glTF being sure to check the "Apply Modifiers" check box while exporting
  4. Preview with something like https://gltf-viewer.donmccurdy.com/ . Note animation will likely be broken or the model may be broken.

I've had an artist prepare a very minimalist sample sample file to demonstrate what happens, but as it is we have about 7 production files we can't export easily due to this issue. We have found a workaround by converting all modifiers into a mesh but this increases the amount of work and we end up having to create extra files so we don't loose our originals.

sample.blend is a simple animation with a Mirror modifier:

sample.blend exported without modifiers:

sample.blend exported with modifiers:

Details

Type
Bug

Event Timeline

@Brecht Van Lommel (brecht) Sorry for not submitting to the correct project! Thanks for the quick action.

Julien DUROURE (julien) closed this task as Invalid.Wed, Sep 11, 9:59 AM

Hello,

This is a known limitation of Blender (not part of the exporter): You can't apply modifier on mesh with shapekeys (even manually).
This is the current behaviour for FBX export too.

@Brecht Van Lommel (brecht) Do you know if there is a long term plan to manage applying modifiers when mesh has shapekeys? (If this is technically doable ?)

I opened a task here to add a warning in option description : https://github.com/KhronosGroup/glTF-Blender-IO/issues/669

Closing this ticket for now

@Julien DUROURE (julien) Thanks for clearing that up! We'll add another step to our workflow and adjust some of our existing models.

I have a few more samples that break things in different ways, all related to this but I was intending to submit separate issues. I'll spare everyone the headache of a bunch of invalid issues and post them here with descriptions - I hope they can be used in the future as tests if there are any plans to "fix" this.

[error] sample animation with a model using modifiers:

  • Basically the above file, but clearly labelled

[working] sample animation on a model where all modifiers have been applied in advance and animation has been added to the modified mesh:

  • This is essentially a "fix" to the issue - as there are no modifiers to apply

[working] sample animation using an armature - *without* modifiers (other than the armature?) and without shape keys:

[now working?] sample animation using armature and shape keys - we had a variety of issues with using armatures and shape keys together in the same glTF export but this *seems* to be working now? - including this sample for reference:

This is an issue which will continue to effect us so if there is going to be any development in the future to try and handle these issues PLEASE tag me so I can try to help.