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Maniphest T64053

Shading, BaseColor duplicated onto transmission on export to OBJ/FBX
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Description

System Information
Operating system: WINDOWS 10
Graphics card: NVIDIA GeForce GTX 1070

Blender Version
Broken: 2.80 beta, b331515d2e47, 2019-05-02

Short description of error
The BaseColor gets copied onto Transmission on export of asset. This causes unwanted transparency to render when asset is imported as a mod into a game.

Exact steps for others to reproduce the error
Step 1: create mesh
Step 2: click "Shading" tab
Step 3: plug in Image Texture into PrincipledBSDF's BaseColor
Step 4: export to obj / fbx
Step 5: import the exported obj / fbx
Step 6: enter "Shading" tab again
Step 7: in the PrincipledBSDF, you will see that the Image Texture plugged into BaseColor is now also duplicated onto Transmission

Related Objects

Event Timeline

Unknown Object (User) created this task.May 1 2019, 9:50 AM
Sebastian Parborg (zeddb) lowered the priority of this task from 90 to 30.May 2 2019, 12:36 PM
Sebastian Parborg (zeddb) added a subscriber: Sebastian Parborg (zeddb).

I can't reproduce this is seems. Could you try the most recent build and see if it is fixed?

If not could you provide a sample .blend file that I can just export to .fbx and it will break?

Unknown Object (User) updated the task description. (Show Details)May 3 2019, 7:15 AM

Just updated. While primitives work. I'm still having trouble otherwise though.

hyperion.zip2 MBDownload

I think that's it ^. Contains the .blend, along with the textures. It's ripped from a game for use as a mod in another.

Sebastian Parborg (zeddb) assigned this task to Bastien Montagne (mont29).May 3 2019, 10:32 AM
Sebastian Parborg (zeddb) raised the priority of this task from 30 to 50.
Bastien Montagne (mont29) added a comment.May 11 2019, 4:05 PM

This is kind of impossible to get correct (expected) behavior in all cases here.

  • We export base color of Principled BSDF also to TransparentColor of FBX, so we also have to link base color texture to TransparentColor in FBX (to be consistent);
  • Some other app (Maya) seem to use FBX's TransparentColor to convey both color and alpha (transparency), so if that one controls alpha with a texture, it will link it to TransparentColor, hence we have to import it…

Either way, we'll break something. Though I would rather be consistent on Blender's side, hence not import TransparentColor's texture as a Principled BSDF's transmission value, I think.

Bastien Montagne (mont29) lowered the priority of this task from 50 to 30.May 11 2019, 4:31 PM

Ah, actually, reason is different, here. The base texture is also linked to the transmission socket because it has alpha. So this is 'by design' behavior, not sure whether we want to keep it or not…

Unknown Object (User) added a comment.May 12 2019, 2:55 AM

Ah, I see now.

After saving the file's _b texture without alpha in my photo editing software, the .fbx no longer imports back into blender without duplication into transmission.

Thank you for going into depth of the cause of this.

Bastien Montagne (mont29) changed the task status from Unknown Status to Unknown Status.May 12 2019, 10:10 PM

Thanks for the confirmation, will archive as expected behavior for now...

kretos (kretoskim) added a subscriber: kretos (kretoskim).Jun 16 2021, 11:23 PM
In T64053#676750, @Bastien Montagne (mont29) wrote:

Ah, actually, reason is different, here. The base texture is also linked to the transmission socket because it has alpha. So this is 'by design' behavior, not sure whether we want to keep it or not…

Thanks soo much it worked