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Blender 2.8 - FBX Normals Export Bug
Closed, ArchivedPublic

Description

System Information
Operating system: Windows 10 Pro May 2019 Update Build 1903
Graphics card: Sapphire Radeon RX 560 2GB GDDR5 Lite

Blender Version
Broken: 2.80 RC1 (Acquired on 13th of July 2017)
Worked: (optional)

Short description of error

Exporting a mesh with the FBX format, and importing into Substance Painter results in certain faces not appearing at all, or seen from "inside out" (seeing the faces inside the model but not the ones you're supposed to see, outside)

Exact steps for others to reproduce the error

Place a cube, copy it 4 times, extrude them in random ways. Then unite their vertices using "F" to create new faces. Proceed to export via FBX for a simple mesh without any bones, leafs or any of that stuff. Y forward, Z up.

Based on the default startup or an attached .blend file (as simple as possible).

Details

Type
Bug

Event Timeline

That is after a recalculation of the vertices. Here is the one without recalculations, which may happen to most people.

on linux OpenSUSE LEAP TW , GPU: GTX690 - NVIDIA drivers 430.34 , CPU: AMD FX-8350, 16G ram
oldblend.blend work fine, no visible issue

I'd like to specify that to achieve the "reveal" of the affected areas, you must use "solidify" with its default presets on the mesh. Exporting without solidify reveals the missing normals in Substance Painter

the "reveal" being the two weird faces overlapping, thus showing the missing ones in Substance

@dark999 (dark999) Try to add & apply a solidify modifier and see if it shows the weird thing.

@Murgeanu Iulian Andrei (IAAndrei) i think my object (red) not had any issue after you apply solify modifier
these are difference from your object and mine

Yep, yours works fine. Over here it's bugged

(look at the green one)

Anyway, that just shows the weird effect on the faces which won't display the normals in substance for me.

In substance painter yours(red) is like this

the internal faces are wrong, what is the direction of the normals for these faces? Do normal work the same way on different software?

In substance painter yours(red) is like this

it is not correct?
If this is correct Blender FBX exporter work fine, this task can be closed and bug was only bad modelling.
If this is not correct, my apologise and you must wait a developer to solve this

I've done the same stuff before, using exactly the same way of extruding in Blender 2.79b, with Substance Painter, and it worked out just fine.

I've modeled some cabinets before, three times. In blender they looked awesome(blender 2.8 + a matcap), but once imported into substance, disaster. The faces that were outside weren't visible apart from the inside. Therefore, we should wait for a dev and see what he says.

Replicated EXACTLY the same method in Blender 2.79b

Blender 2.8 RC1{F7606469}

Same method, this time the error shows up, proving that blender has the error here.

My machine:
CPU: Intel Xeon X3210
RAM: Quad Channel DDR2 8GB (2gb sticks x4)
GPU: AMD Sapphire Radeon RX 560 Lite 2gb GDDR5
MOBO: ASUS P5B-Deluxe LGA-775

All the cubes we're connected vertice by vertice, to make a face. Same result can be achieved by using the line select(two vertices at once).

These are the FBX export settings for BOTH 2.79b and 2.8:

Messing with the "Forward" and "Up" axis doesn't do anything to fix that.
Messing with the smoothing type "normals only / face/ edge" gives the same result when it comes to this bug.

Bastien Montagne (mont29) closed this task as Archived.Jul 16 2019, 2:46 PM

This task looks much more like a user-helping forum thread than a bug report…

  • That mesh (the one from the first .blend file provided here) is non-manifold. I do not have Substance, but would not be surprised it has another way than Blender to rebuild normals, especially in those fuzzy cases.
  • Doing exactly the same sequence of extrusions in 2.79 and 2.80 may not generate the exact same topology (their might be differences in orders especially, of both vertices and faces, and face windings). That is no bug, merely changes in the software.
  • Exporting that file in FBX and importing it back in Blender gives exact same mesh (besides the data from conversion to/from FBX, i.e. things like sharp edges and custom normals data layer).

So I do not see any evidence of a bug here. We do not handle user support on this tracker, only bug reports. User forums like blenderartists.org or blender.stackexchange.com and our devtalk should be used for that matter.