Tangents/bitangents missing from exported FBX model #39792

New Issue

Darren Keese · 2014-04-19T03:23:00+02:00

Darren Keese commented

2014-04-19 03:23:00 +02:00

System Information
Windows 7 64bit

Blender Version
2.70 4ed16bc

When exporting a static model as FBX, tangents and bitangents are missing in the .fbx file.

Exact steps for others to reproduce the error
Default new file.
Select the cube and add a material.
Under the Material's Shading section, check Tangent Shading. (Unnecessary to reproduce bug, but I thought it might be required.)
Add a new image file texture to the material. Create a new one and assign Color Grid to make it visible.
Set texture's mapping coordinates to UV and check it's Influence box for Normal under Geometry.
Go to UV Editing interface and perform cube projection on all vertices.
Go to File->Export->Autodesk FBX
Check Selected Objects and Tangent Space. Save the fbx file.
Observe, using FBX SDK that there are no tangents or bitangents in the fbx file when it is imported. This happens with the binary. With the ASCII export, I can read the file and see no tangents or bitangents.

fbx_tangents.blend

**System Information** Windows 7 64bit **Blender Version** 2.70 4ed16bc When exporting a static model as FBX, tangents and bitangents are missing in the .fbx file. **Exact steps for others to reproduce the error** Default new file. Select the cube and add a material. Under the Material's Shading section, check Tangent Shading. (Unnecessary to reproduce bug, but I thought it might be required.) Add a new image file texture to the material. Create a new one and assign Color Grid to make it visible. Set texture's mapping coordinates to UV and check it's Influence box for Normal under Geometry. Go to UV Editing interface and perform cube projection on all vertices. Go to File->Export->Autodesk FBX Check Selected Objects and Tangent Space. Save the fbx file. Observe, using FBX SDK that there are no tangents or bitangents in the fbx file when it is imported. This happens with the binary. With the ASCII export, I can read the file and see no tangents or bitangents. [fbx_tangents.blend](https://archive.blender.org/developer/F85223/fbx_tangents.blend)

Darren Keese commented

2014-04-19 03:23:00 +02:00

Changed status to: 'Open'

Bastien Montagne was assigned by Darren Keese

2014-04-19 03:23:00 +02:00

Darren Keese commented

2014-04-19 03:23:00 +02:00

Added subscriber: @cypherdare

Darren Keese commented

2014-04-19 03:26:03 +02:00

To clarify, I know tangents may not be in a mesh imported to Blender from FBX. I mean that when I use a third party program (in my case, libgdx/fbx-conv) that relies on the FBX SDK to import and translate the mesh, the mesh does not have tangent or bitangent attributes for the vertices.

Thomas Dinges commented

2014-04-19 22:49:07 +02:00

Added subscriber: @ThomasDinges

Bastien Montagne commented

2014-04-23 17:26:29 +02:00

Legacy ASCII 6.1 exporter does not support tangents, this is expected.

I just fixed a typo in bin 7.4 exporter, but it does not seems to be enough for Unity (though data are in FBX mesh, likely yet another tiny details that breaks it). Could you please attach a valid FBX file having working tangents/binormals (the simpler the better)? It should be saved with a recent version of Maya/Max/... (i.e. be in the 7.x family of FBX formats).

Legacy ASCII 6.1 exporter does not support tangents, this is expected. I just fixed a typo in bin 7.4 exporter, but it does not seems to be enough for Unity (though data are in FBX mesh, likely yet another tiny details that breaks it). Could you please attach a valid FBX file having working tangents/binormals (the simpler the better)? It should be saved with a recent version of Maya/Max/... (i.e. be in the 7.x family of FBX formats).

Darren Keese commented

2014-04-24 04:47:10 +02:00

I don't use anything besides Blender, but I can try downloading a trial of one of the Autodesk programs tomorrow night and making one.

I haven't used Unity in a while, but I seem to remember Unity generating its own tangents when importing a model, if you have set a normal map on the model correctly. So I'm not sure if it just ignores FBX tangents and generates its own. And maybe it is not showing tangents because you don't have the materials set up just so in Unity. Maybe I can experiment with that this weekend.

I'm personally interested in using this with LibGDX, which uses the LibGDX fbx-conv program to convert FBX files into their own G3D format. I looked over the source of fbx-conv, and it seems to rely completely on the FBX SDK to acquire the mesh. So as far as I can tell from the source, tangents will definitely be in the exported G3D file if they were in the original FBX file, provided the FBX SDK isn't buggy.

So this might be a good way to test the validity of the FBX file's tangents. You can export G3D as a JSON file instead of binary so you can easily see if the tangents are there. The vertex attributes are listed right at the top of the JSON file.

Example: fbx-conv -o G3DJ input.fbx output.g3dj

Can you attach an FBX file that you've exported with your latest? I'd like to see how it does with fbx-conv if you don't have the time.

I don't use anything besides Blender, but I can try downloading a trial of one of the Autodesk programs tomorrow night and making one. I haven't used Unity in a while, but I seem to remember Unity generating its own tangents when importing a model, if you have set a normal map on the model correctly. So I'm not sure if it just ignores FBX tangents and generates its own. And maybe it is not showing tangents because you don't have the materials set up just so in Unity. Maybe I can experiment with that this weekend. I'm personally interested in using this with LibGDX, which uses the LibGDX [fbx-conv ](https://github.com/libgdx/fbx-conv) program to convert FBX files into their own G3D format. I looked over the source of **fbx-conv**, and it seems to rely completely on the FBX SDK to acquire the mesh. So as far as I can tell from the source, tangents will definitely be in the exported G3D file if they were in the original FBX file, provided the FBX SDK isn't buggy. So this might be a good way to test the validity of the FBX file's tangents. You can export G3D as a JSON file instead of binary so you can easily see if the tangents are there. The vertex attributes are listed right at the top of the JSON file. Example: `fbx-conv -o G3DJ input.fbx output.g3dj` Can you attach an FBX file that you've exported with your latest? I'd like to see how it does with fbx-conv if you don't have the time.

Bastien Montagne commented

2014-04-24 09:15:12 +02:00

untitled_blend.fbx

Note Unity computes tangents by default, but has an option to import them instead (and with this files, this generates a warning saying there is no tangent nor binormal data). And since Unity uses FBXSDK like everyone else but Blender…

[untitled_blend.fbx](https://archive.blender.org/developer/F85788/untitled_blend.fbx) Note Unity computes tangents by default, but has an option to import them instead (and with this files, this generates a warning saying there is no tangent nor binormal data). And since Unity uses FBXSDK like everyone else but Blender…

Darren Keese commented

2014-04-24 14:18:10 +02:00

OK, same result in fbx-conv, no tangent or bitangent attributes, which follows what you said since they both use the FBX SDK. I'll try to get you that Maya-exported file tonight.

Darren Keese commented

2014-04-25 13:58:49 +02:00

I didn't have enough time to check this file over after exporting. Took me a while to figure out how to make it since I haven't used Maya since the Maya PLE days about 10 years ago.

It may not have normals and bitangents and bitangents. If not, I'll try to redo it tonight.

simple_block.fbx

I didn't have enough time to check this file over after exporting. Took me a while to figure out how to make it since I haven't used Maya since the Maya PLE days about 10 years ago. It may not have normals and bitangents and bitangents. If not, I'll try to redo it tonight. [simple_block.fbx](https://archive.blender.org/developer/F85888/simple_block.fbx)

blender-admin commented

2014-04-25 14:39:40 +02:00

This issue was referenced by blender/blender-addons@7aebdfb396

This issue was referenced by blender/blender-addons@7aebdfb396ef1a7899f361bf429dbeba4fdab67b

Bastien Montagne commented

2014-04-25 14:44:19 +02:00

Changed status from 'Open' to: 'Resolved'

Bastien Montagne closed this issue

2014-04-25 14:44:19 +02:00

Bastien Montagne commented

2014-04-25 14:44:19 +02:00

Closed by commit blender/blender-addons@7aebdfb396.

Bastien Montagne commented

2014-04-25 14:47:34 +02:00

@cypherdare Thanks for the file (ultimately, was yet another stupid tiny detail missing in generated FBX :/ ). Could you please test one of our next nightly builds tomorrow to check it actually works as expected? All I can say is that Unity now seems to load them OK (no warning nor error message)…

@cypherdare Thanks for the file (ultimately, was yet another stupid tiny detail missing in generated FBX :/ ). Could you please test one of our next [nightly builds](http://builder.blender.org/download) tomorrow to check it actually works as expected? All I can say is that Unity now seems to load them OK (no warning nor error message)…

Darren Keese commented

2014-04-27 03:28:07 +02:00

It's working in LibGDX via fbx-conv. Thank you for working through this! It's going to be well appreciated by many indie game developers, I think.

Bastien Montagne commented

2014-04-27 08:54:45 +02:00

Cool, and thanks for the feedback! :)

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Tangents/bitangents missing from exported FBX model #39792