FBX export lacking image paths for 3rd party applications (eg unity) #74070

New Issue

Frankie Hobbins · 2020-02-21T10:53:55+01:00

Frankie Hobbins commented

2020-02-21 10:53:55 +01:00

System Information
win10
2080ti

Blender Version
2.82

Short description of error
When exporting FBX files it is possible to embed image paths for third party applications such as unity3d to use to create materials for their shaders.
With blender eevee Principled BSDF shader you can easily use the same textures Unity needs for its shader.

When you export as FBX and bring into unity, unity will automatically hook up the "Base Color" texture in the material. But ignores the other textures.

On closer inspection opening the FBX file in a text editor reveals that only the path for the "Base Color" exists in the FBX data. This must explain why unity isn't able to rebuild the material.

Exact steps for others to reproduce the error
Open blend file
double check images are attached to material correctly
export FBX (or open the existing one)
open FBX in a text editor
search for "green_metal_rust_diff_2k" and notice how it appears
search for either of the other 2 materials and notice how it doesn't appear

Extra notes
Unity uses a packed "mask map" where Red channel: Metallic mask, Green channel: Ambient occlusion. Blue channel: Detail map mask. Alpha channel: Smoothness.
This needs to be unpacked with a separate RGB node in blender.

FBX filepath bug.zip

**System Information** win10 2080ti **Blender Version** 2.82 **Short description of error** When exporting FBX files it is possible to embed image paths for third party applications such as unity3d to use to create materials for their shaders. With blender eevee Principled BSDF shader you can easily use the same textures Unity needs for its shader. When you export as FBX and bring into unity, unity will automatically hook up the "Base Color" texture in the material. But ignores the other textures. On closer inspection opening the FBX file in a text editor reveals that only the path for the "Base Color" exists in the FBX data. This must explain why unity isn't able to rebuild the material. **Exact steps for others to reproduce the error** Open blend file double check images are attached to material correctly export FBX (or open the existing one) open FBX in a text editor search for "green_metal_rust_diff_2k" and notice how it appears search for either of the other 2 materials and notice how it doesn't appear **Extra notes** Unity uses a packed "mask map" where Red channel: Metallic mask, Green channel: Ambient occlusion. Blue channel: Detail map mask. Alpha channel: Smoothness. This needs to be unpacked with a separate RGB node in blender. [FBX filepath bug.zip](https://archive.blender.org/developer/F8356656/FBX_filepath_bug.zip)

Frankie Hobbins commented

2020-02-21 10:53:55 +01:00

Added subscriber: @FrankieHobbins

Frankie Hobbins commented

2020-02-21 11:03:31 +01:00

After reporting I thought I would check some more things.

The separate RGB node stops the link between the mask image and the node connection. Without the node you can save links to whatever the metallic/specular slots have plugged into them.
It would be ideal if this node didn't break and the links and the image trace could continue past it.
Normal map texture is not getting exported whatever I do.

After reporting I thought I would check some more things. - The separate RGB node stops the link between the mask image and the node connection. Without the node you can save links to whatever the metallic/specular slots have plugged into them. It would be ideal if this node didn't break and the links and the image trace could continue past it. - Normal map texture is not getting exported whatever I do.

Frankie Hobbins commented

2020-02-21 12:07:31 +01:00

Someone just pointed out to me that the normal map path will get exported if I put a normal map node between the image node and the shader normal input.

I suppose that has made this bug invalid, however if possible can I have clarity on the "mask map" export path so I can file a but report to unity that its possible to output from blender but unity is failing to import?

Someone just pointed out to me that the normal map path will get exported if I put a normal map node between the image node and the shader normal input. I suppose that has made this bug invalid, however if possible can I have clarity on the "mask map" export path so I can file a but report to unity that its possible to output from blender but unity is failing to import?

Philipp Oeser commented

2020-02-21 13:04:24 +01:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2020-02-21 13:04:24 +01:00

This issue is coming up once in a while.

It is documented though:
https://docs.blender.org/manual/en/2.82/addons/import_export/node_shaders_info.html

Someone just pointed out to me that the normal map path will get exported if I put a normal map node between the image node and the shader normal input.

That is correct, see the documentation also

Unity uses a packed "mask map" where Red channel: Metallic mask, Green channel: Ambient occlusion. Blue channel: Detail map mask. Alpha channel: Smoothness.
Can I have clarity on the "mask map" export path so I can file a but report to unity that its possible to output from blender but unity is failing to import?

I am afraid that is not possible to support that pipeline directly from blender atm. (textures need to be directly linked to the sockets, no other nodes in between allowed [except normalmap]-- would be hard to keeps this symmetrical like the docs mention)
I am confused though:

can Unity HDRP only work with mask maps? (it is not possible to have different maps for metallic, occlusion, roughness?)
how does Unity import/export these to/from FBX? (it expects the same file to be mapped to metallic, occlusion, roughness in FBX and then picks the corresponding channel by itself?)
(in other words: if you get rid of the Separate RGB in your file and map the green_metal_rust_mask_2k.png directly to Metallic & Roughness just for export purposes, does Unity read the FBX correctly into their own mask maps?)

This issue is coming up once in a while. It is documented though: https://docs.blender.org/manual/en/2.82/addons/import_export/node_shaders_info.html > Someone just pointed out to me that the normal map path will get exported if I put a normal map node between the image node and the shader normal input. That is correct, see the documentation also > Unity uses a packed "mask map" where Red channel: Metallic mask, Green channel: Ambient occlusion. Blue channel: Detail map mask. Alpha channel: Smoothness. > Can I have clarity on the "mask map" export path so I can file a but report to unity that its possible to output from blender but unity is failing to import? I am afraid that is not possible to support that pipeline directly from blender atm. (textures need to be directly linked to the sockets, no other nodes in between allowed [except normalmap]-- would be hard to keeps this symmetrical like the docs mention) I am confused though: - can Unity HDRP only work with mask maps? (it is not possible to have different maps for metallic, occlusion, roughness?) - how does Unity import/export these to/from FBX? (it expects the same file to be mapped to metallic, occlusion, roughness in FBX and then picks the corresponding channel by itself?) - (in other words: if you get rid of the `Separate RGB` in your file and map the `green_metal_rust_mask_2k.png` directly to Metallic & Roughness just for export purposes, does Unity read the FBX correctly into their own mask maps?)

Frankie Hobbins commented

2020-02-21 13:29:19 +01:00

Unity HDRP/Lit shader only works with mask maps. It's its possible for the user to make their own shader with the built in shader graph that would allow separate images to replace the mask map. However you cannot change the shader in the embedded material with so I don't think anything else would work.

I tried remapping images directly to the shader nodes and they appear in the FBX file but nothing seems to get picked up by unity.

My hope is now if we had Blender exporting the path to Metallic or Roughness images though the Separate RGB (and actually we need an invert node for the roughness) node we could go to Unity and tell them to assign them it to their mask map.

Unity HDRP/Lit shader only works with mask maps. It's its possible for the user to make their own shader with the built in shader graph that would allow separate images to replace the mask map. However you cannot change the shader in the embedded material with so I don't think anything else would work. I tried remapping images directly to the shader nodes and they appear in the FBX file but nothing seems to get picked up by unity. My hope is now if we had Blender exporting the path to Metallic or Roughness images though the Separate RGB (and actually we need an invert node for the roughness) node we could go to Unity and tell them to assign them it to their mask map.

Philipp Oeser commented

2020-02-21 14:07:56 +01:00

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

Philipp Oeser closed this issue

2020-02-21 14:07:56 +01:00

Philipp Oeser self-assigned this 2020-02-21 14:07:56 +01:00

Philipp Oeser commented

2020-02-21 14:07:56 +01:00

In #74070#877450, @FrankieHobbins wrote:
I tried remapping images directly to the shader nodes and they appear in the FBX file but nothing seems to get picked up by unity.
My hope is now if we had Blender exporting the path to Metallic or Roughness images though the Separate RGB (and actually we need an invert node for the roughness) node we could go to Unity and tell them to assign them it to their mask map.

I dont think it would make a difference if paths were exported even with the Separate RGB still in the nodegraph (this Separate RGB will never be included in FBX, afaict FBX has no concept/knowledge of shader nodes really, so you'd have the same texture hooked up to Metallic and Roughness in the FBX -- and this is what seems to already fail in Unity...)

Sorry to say that I am not very familiar with the HDRP/Lit shader workflow, but it seems strange to me that there would be no way to pack the channels from [possibly separate] textures inside Unity? Or that Unity simply doesnt pick those PBR textures up in the HDRP case at all?

In any case, this would not be considered a bug on blenders side for now, will have to close this I am afraid...
If you get an answer from Unity on how this should work (FBX PBR textures to channel packed mask maps) or if you find a place where this is documented, please still drop a message here, I'd be interested :)

> In #74070#877450, @FrankieHobbins wrote: > I tried remapping images directly to the shader nodes and they appear in the FBX file but nothing seems to get picked up by unity. > My hope is now if we had Blender exporting the path to Metallic or Roughness images though the Separate RGB (and actually we need an invert node for the roughness) node we could go to Unity and tell them to assign them it to their mask map. I dont think it would make a difference if paths were exported even with the `Separate RGB` still in the nodegraph (this Separate RGB will never be included in FBX, afaict FBX has no concept/knowledge of shader nodes really, so you'd have the same texture hooked up to Metallic and Roughness in the FBX -- and this is what seems to already fail in Unity...) Sorry to say that I am not very familiar with the HDRP/Lit shader workflow, but it seems strange to me that there would be no way to pack the channels from [possibly separate] textures inside Unity? Or that Unity simply doesnt pick those PBR textures up in the HDRP case at all? In any case, this would not be considered a bug on blenders side for now, will have to close this I am afraid... If you get an answer from Unity on how this should work (FBX PBR textures to channel packed mask maps) or if you find a place where this is documented, please still drop a message here, I'd be interested :)

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FBX export lacking image paths for 3rd party applications (eg unity) #74070