FBX Export - Some normals appear to be flipped #46797
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Reference: blender/blender-addons#46797
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System Information
Windows 10, HD Radeon 7950
Blender Version
Broken: Current version - 2.76. Broken first in 2.75
Worked: 2.74
Specifically,
Worked in commit
f30fc86ab5Broken in commit
87e95103c5(ran git bisect)
Short description of error
When I export a certain model from Blender, using the FBX Binary exporter (ASCII does not have this problem), then try to import it into Substance Designer 4 (I have not tried 5, this may be a bug in 4, but, it was working before the above commit), then in Substance Designer, try to bake normals for the mesh (I try to bake the normals from the mesh onto itself, is the simplest test), then about half of the normals are flipped on the generated normal map. They correspond with certain manifolds within the mesh. If I flip the normals for those in Blender (so that in Blender, they are facing the wrong way), then the generated normal map is correct.
Exact steps for others to reproduce the error
Take the above .blend file, export the one mesh using the FBX Binary exporter. I don't know if any other 3d program that can load .fbx files will display the problem, but if you have Substance Designer...link the fbx file, right click on the model and go to "Bake Model Information", add a "normal map from mesh" baker, for the high definition mesh, select the same mesh, then bake it. Other settings won't matter.
fbx-export-problem.blend
Changed status to: 'Open'
Added subscriber: @Snea
Only way I could understand that issue is, if you are using the experimental
Apply Transformexport option… Are you?Afraid not, it's unchecked.
Then I do not see what is happening here, would expect a bug from SD4 (at least, re-importing FBX inside Blender gives perfectly valid normals). Do you have by any chance opportunity to try with another 'FBX reference' software (like Maya or 3dsmax)?
Other random idea - are you exporting tangent space? Afaik this is used to bake normals, and different applications tend to generate different tangent spaces, could be something to dig out (though I would see no reason for this to break on a change in global scaling area :( ).
I tried exporting with and without tangent space, and it made no difference. I would have checked with other FBX programs but I don't have any. I could try importing it into Unity, I suppose, but you're probably right, a weird SD4 glitch....
Okay I just confirmed that Substance Designer 5 does not have this problem. Looks like it was a bug on their end...kind of an expensive fix but so be it.
Changed status from 'Open' to: 'Archived'
OK, archiving this report then, thanks for the followup. :)