gltf exporter exports incorrect transforms when exporting nodes that have a rotation or scale other than the identity #83131

New Issue

Mark McKay · 2020-11-27T22:48:17+01:00

Mark McKay commented

2020-11-27 22:48:17 +01:00

System Information
Operating system: Windows
Graphics card: ATF

Blender Version
Broken: 2.92.0 Alpha, fbdf1af35550
Worked: never

When I try to export a file in gltf form, any object nodes that link to a collection in another file and which have a rotation or scale applied to them export an incorrect transform in the final file.

Exact steps for others to reproduce the error
Create a new blend file. Create a monkey object and add it to the collection 'Monkey".
Create a second blend file. Create a link to the Monkey collection in the first file.
Select your linked object. Press Ctrl-D and move the object somewhere else in your scene. Rotate it about an axis or scale it. Do this several times with several objects.
Export your scene as a gltf file.
Open the gltf in a viewer. You will see the objects that you applied rotations or scales to in incorrect locations.

How to fix
I've come up with a patch. In the latest build of blender, in the gltf2_blender_gather_nodes.py file you need to replace lines 426-427 with

      offset = -__convert_swizzle_location(
          blender_object.instance_collection.instance_offset, export_settings)

      s = Matrix.Diagonal(sca).to_4x4()
      r = rot.to_matrix().to_4x4() 
      t = Matrix.Translation(trans).to_4x4()
      o = Matrix.Translation(offset).to_4x4()
      m = t @ r @ s @ o

      trans = m.translation

**System Information** Operating system: Windows Graphics card: ATF **Blender Version** Broken: 2.92.0 Alpha, fbdf1af35550 Worked: never When I try to export a file in gltf form, any object nodes that link to a collection in another file and which have a rotation or scale applied to them export an incorrect transform in the final file. **Exact steps for others to reproduce the error** Create a new blend file. Create a monkey object and add it to the collection 'Monkey". Create a second blend file. Create a link to the Monkey collection in the first file. Select your linked object. Press Ctrl-D and move the object somewhere else in your scene. Rotate it about an axis or scale it. Do this several times with several objects. Export your scene as a gltf file. Open the gltf in a viewer. You will see the objects that you applied rotations or scales to in incorrect locations. **How to fix** I've come up with a patch. In the latest build of blender, in the gltf2_blender_gather_nodes.py file you need to replace lines 426-427 with ``` offset = -__convert_swizzle_location( blender_object.instance_collection.instance_offset, export_settings) ``` ``` s = Matrix.Diagonal(sca).to_4x4() r = rot.to_matrix().to_4x4() t = Matrix.Translation(trans).to_4x4() o = Matrix.Translation(offset).to_4x4() m = t @ r @ s @ o ``` ``` trans = m.translation

Mark McKay commented

2020-11-27 22:48:17 +01:00

Added subscriber: @kitfox

Mark McKay commented

2020-11-27 22:56:20 +01:00

Not sure it's the same thing. The issue you linked to is for bones, not collections.

Julien Duroure commented

2020-12-01 14:53:20 +01:00

Added subscriber: @JulienDuroure

Julien Duroure commented

2020-12-01 14:53:20 +01:00

I created a ticket in upstream repository: https://github.com/KhronosGroup/glTF-Blender-IO/issues/1280

Julien Duroure commented

2020-12-06 08:11:10 +01:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Julien Duroure commented

2020-12-06 08:11:10 +01:00

I can't reproduce.

What gltf viewer are you using?
Please provide example files.

Here are my files and screenshot from https://gltf-viewer.donmccurdy.com/

monkeys.zip

I can't reproduce. What gltf viewer are you using? Please provide example files. Here are my files and screenshot from https://gltf-viewer.donmccurdy.com/ ![image.png](https://archive.blender.org/developer/F9480224/image.png) [monkeys.zip](https://archive.blender.org/developer/F9480227/monkeys.zip)

Julien Duroure commented

2020-12-06 20:01:35 +01:00

Changed status from 'Needs User Info' to: 'Confirmed'