FBX does not import polygons smooth groups properly #81416

New Issue

David Oroian · 2020-10-03T16:41:29+02:00

David Oroian commented

2020-10-03 16:41:29 +02:00

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.38

Blender Version
Broken: version: 2.90.0, branch: master, commit date: 2020-08-31 11:26, hash: blender/blender@0330d1af29
Worked: (newest version of Blender that worked as expected)

Short description of error
Importing FBX files always destroys the normals.

Exact steps for others to reproduce the error
All FBX files opened in blender have their normals broken as soon as you unlock them. (tested on multiple versions- 2.81, 2.83.1, 2.90.0)
Sharp edges are always either missing or get randomly placed.FBX import results in broken normals.mp4
This video shows the opening of the model with broken and unusable shading.

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.38 **Blender Version** Broken: version: 2.90.0, branch: master, commit date: 2020-08-31 11:26, hash: `blender/blender@0330d1af29` Worked: (newest version of Blender that worked as expected) **Short description of error** Importing FBX files always destroys the normals. **Exact steps for others to reproduce the error** All FBX files opened in blender have their normals broken as soon as you unlock them. (tested on multiple versions- 2.81, 2.83.1, 2.90.0) Sharp edges are always either missing or get randomly placed.[FBX import results in broken normals.mp4](https://archive.blender.org/developer/F8951006/FBX_import_results_in_broken_normals.mp4) This video shows the opening of the model with broken and unusable shading.

David Oroian commented

2020-10-03 16:41:29 +02:00

Added subscriber: @David-Oroian

Octave C commented

2020-10-03 18:10:22 +02:00

Added subscriber: @toctave

Octave C commented

2020-10-03 18:10:22 +02:00

Hello, could you post the .fbx file you used in the demo, to have a reference point? Also, are you certain that this file contains the right information? As in, does opening it in another software show different results ?

Also, can you explain what you mean by broken normals ? On what you sent, it seems like the problem is only the hard edges.

Hello, could you post the .fbx file you used in the demo, to have a reference point? Also, are you certain that this file contains the right information? As in, does opening it in another software show different results ? Also, can you explain what you mean by broken normals ? On what you sent, it seems like the problem is only the hard edges.

David Oroian commented

2020-10-04 07:44:06 +02:00

Hi, the problem does indeed have to do with hard edges. Hard edges and the normals go hand in hand. Having good normals when importing does not mean anything if when you disable the locked normals all the shading goes bad (because of the missing or wrongly placed hard edges).

Here I will attach a blender file containing a part of the model you saw previously. It has 2 collections: the original import and one where I fixed the shading. Feel free to test exporting the fixed version and importing it again. 100% of the time you will have randomly placed hard edges.Shading fbx test.blend

FBX from Rizom.fbx

Hi, the problem does indeed have to do with hard edges. Hard edges and the normals go hand in hand. Having good normals when importing does not mean anything if when you disable the locked normals all the shading goes bad (because of the missing or wrongly placed hard edges). Here I will attach a blender file containing a part of the model you saw previously. It has 2 collections: the original import and one where I fixed the shading. Feel free to test exporting the fixed version and importing it again. 100% of the time you will have randomly placed hard edges.[Shading fbx test.blend](https://archive.blender.org/developer/F8953570/Shading_fbx_test.blend) [FBX from Rizom.fbx](https://archive.blender.org/developer/F8953587/FBX_from_Rizom.fbx)

Octave C commented

2020-10-04 20:34:26 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Octave C self-assigned this 2020-10-04 20:34:26 +02:00

Octave C commented

2020-10-04 20:34:26 +02:00

Reproduced in Blender 2.90.0 / Ubuntu 18.04

I'll look into the import/export code and let you know

Reproduced in Blender 2.90.0 / Ubuntu 18.04 I'll look into the import/export code and let you know

Octave C commented

2020-10-05 10:24:31 +02:00

This is apparently an issue with how smoothing data is handled when importing fbx. If you exported the fbx file yourself, you can use the "Edge" smoothing option in the "Geometry" section of the export, which will correctly export sharp edge data.

Otherwise, please add more details about how your fbx file was created : 3D software (with version), export options, etc.

This is apparently an issue with how smoothing data is handled when importing fbx. If you exported the fbx file yourself, you can use the "Edge" smoothing option in the "Geometry" section of the export, which will correctly export sharp edge data. Otherwise, please add more details about how your fbx file was created : 3D software (with version), export options, etc.

David Oroian commented

2020-10-09 11:59:43 +02:00

This FBX is created by RizomUV with the default fbx preset.
Tested in Maya 2020 the file opens up perfectly without any missing hard edges or extra ones.

I also tested exporting the mesh from blender with the "edge" smoothing option and I no longer get extra hard edges when importing FBX fiels exported from blender. Thank you for that!

The issue with the FBX exported from RizomUV still stands.

This FBX is created by RizomUV with the default fbx preset. ![image.png](https://archive.blender.org/developer/F8970847/image.png) Tested in Maya 2020 the file opens up perfectly without any missing hard edges or extra ones. I also tested exporting the mesh from blender with the "edge" smoothing option and I no longer get extra hard edges when importing FBX fiels exported from blender. Thank you for that! The issue with the FBX exported from RizomUV still stands.

Bastien Montagne commented

2020-10-13 18:32:53 +02:00

Added subscriber: @mont29

Bastien Montagne commented

2020-10-13 18:32:53 +02:00

This FBX uses bitflags based smoothing of polygons (aka poly smooth groups), support for this is not really implemented (we just use it as a boolean, so all different smooth groups get mixed together). This i a known TODO, not a bug.

Bastien Montagne changed title from ~~Fbx imports with broken normals~~ to FBX does not import polygons smooth groups properly

2020-10-13 18:34:01 +02:00

Bastien Montagne commented

2020-10-13 18:35:15 +02:00

Closed as duplicate of #69408

Bastien Montagne closed this issue

2020-10-13 18:35:15 +02:00

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

FBX does not import polygons smooth groups properly #81416