Material ID instead of Materials in use #66709

New Issue

Emerson Rosa · 2019-07-11T15:55:19+02:00

Emerson Rosa commented

2019-07-11 15:55:19 +02:00

System Information
Operating system: Windows 10
Graphics card: GTX 1070

Blender Version
2.80 Beta, 700346d377, 2019-03-30 19:37

Short description
Missing "material slots" or "material id number" inside Blender.

Full explanation
I'll give an example to explain the bug/issue:

I have a geometry inside Unreal Engine with 10 material slots/ids:

9 slots are using the same material (Ex.: Material01)
the remaining slot is using a different one (Ex.: Material02)

Each of the 10 slots affect a different part of the mesh which I may have to modify. When I export that mesh and import in Blender, it only shows two materials (Material01 and Material02), so I can't access the different areas of the model (from the 10 different IDs/Slots). If I import that same FBX in 3DSMax, for instance, it will show all the slots regardless of the material being the same or not.

In short: It would be nice to have a way to access that "Polygon's Material ID" information inside Blender, not just the different materials applied to a given geometry.

I've attached a FBX as an example. It has 6 different material IDs but only 2 different materials applied. In Blender it only shows both the different materials.
SM_Cube_Example.fbx

**System Information** Operating system: Windows 10 Graphics card: GTX 1070 **Blender Version** 2.80 Beta, 700346d377dd, 2019-03-30 19:37 **Short description** Missing "material slots" or "material id number" inside Blender. **Full explanation** I'll give an example to explain the bug/issue: I have a geometry inside Unreal Engine with 10 material slots/ids: - 9 slots are using the same material (Ex.: Material01) - the remaining slot is using a different one (Ex.: Material02) Each of the 10 slots affect a different part of the mesh which I may have to modify. When I export that mesh and import in Blender, it only shows two materials (Material01 and Material02), so I can't access the different areas of the model (from the 10 different IDs/Slots). If I import that same FBX in 3DSMax, for instance, it will show all the slots regardless of the material being the same or not. In short: It would be nice to have a way to access that "Polygon's Material ID" information inside Blender, not just the different materials applied to a given geometry. **I've attached a FBX as an example. It has 6 different material IDs but only 2 different materials applied. In Blender it only shows both the different materials.** [SM_Cube_Example.fbx](https://archive.blender.org/developer/F7592843/SM_Cube_Example.fbx)

Emerson Rosa commented

2019-07-11 15:55:19 +02:00

Added subscriber: @e1412

Sybren A. Stüvel commented

2019-07-11 16:31:18 +02:00

Added subscriber: @dr.sybren

Sybren A. Stüvel commented

2019-07-11 16:31:18 +02:00

This looks like a feature request (support material IDs rather than just materials) for the FBX importer; not sure though, could be considered a bug. At least re-test it with the latest build of Blender 2.80 from https://builder.blender.org/download/.

Emerson Rosa commented

2019-07-11 18:55:27 +02:00

Hey, Sybren!

Just tested with the latest version and the issue is still there. It's not just for FBX files, I tested with OBJ as well and it seems that Blender "merges" equal materials into the same ID (exporting back to Unreal from Blender (for instance), all the different Slots are gone, and just the unique material IDs remain). Using the same example above, instead of keeping 10 material slots, it comes back from Blender with just 2.

It could be indeed considered a feature request, if you think it fits better that way! How can I do that?

Hey, Sybren! Just tested with the latest version and the issue is still there. It's not just for FBX files, I tested with OBJ as well and it seems that Blender "merges" equal materials into the same ID (exporting back to Unreal from Blender (for instance), all the different Slots are gone, and just the unique material IDs remain). Using the same example above, instead of keeping 10 material slots, it comes back from Blender with just 2. It could be indeed considered a feature request, if you think it fits better that way! How can I do that?

Lucas Leme commented

2019-07-12 15:34:53 +02:00

Added subscriber: @LucasLeme

Sybren A. Stüvel commented

2019-07-16 15:42:02 +02:00

Changed status from 'Open' to: 'Archived'

Sybren A. Stüvel closed this issue

2019-07-16 15:42:02 +02:00

Sybren A. Stüvel self-assigned this 2019-07-16 15:42:02 +02:00

Sybren A. Stüvel commented

2019-07-16 15:42:02 +02:00

@e1412 You can discuss new features at https://blender.community/c/rightclickselect. There you can discuss ideas with others, and flesh them out so that they're in such a detailed state that a developer can pick them up and work on an implementation without having too many open ends to think about.

Nathan Letwory commented

2019-07-29 09:29:41 +02:00

Added subscriber: @jesterking

Nathan Letwory commented

2019-07-29 09:29:41 +02:00

@e1412 Did you test importing the FBX and OBJ files back into Unreal? Do the material indices survive the roundtrip?

From the files you linked to in https://blender.community/c/rightclickselect/4ydbbc/#5d2ed47dd3ac8b621cede009 I have a hard time seeing it could actually work, especially for the OBJ format, but also really for FBX.

@e1412 Did you test importing the FBX and OBJ files back into Unreal? Do the material indices survive the roundtrip? From the files you linked to in https://blender.community/c/rightclickselect/4ydbbc/#5d2ed47dd3ac8b621cede009 I have a hard time seeing it could actually work, especially for the OBJ format, but also really for FBX.

Emerson Rosa commented

2019-07-29 15:12:33 +02:00

In #66709#738239, @jesterking wrote:
@e1412 Did you test importing the FBX and OBJ files back into Unreal? Do the material indices survive the roundtrip?

From the files you linked to in https://blender.community/c/rightclickselect/4ydbbc/#5d2ed47dd3ac8b621cede009 I have a hard time seeing it could actually work, especially for the OBJ format, but also really for FBX.

Hey, Nathan! It seems it doesn't survive the roundtrip indeed. Just exporting and reimporting to Unreal and the IDs are merged. But the thing is that 3DSMax is able to get that information from the FBX somehow. If only there was a way to export from Unreal in the ASCII format to check it :T

Unreal just exports in FBX, maybe the OBJ doesn't support that "instanced" information. As I mentioned on the other link, I think it makes sense for the FBX to use this section for the IDs:

LayerElementMaterial: 0 {
Version: 101
Name: ""
MappingInformationType: "ByPolygon"
ReferenceInformationType: "IndexToDirect"
Materials: *12 {
a: 0,0,0,0,1,1,2,2,3,3,4,4
}
}

That cube has 12 triangles, so each of those numbers (from 0 to 4 - probably refering to the 5 materials applied (I said 6 by mistaken)) may be linked to the order of polygons inside the FBX. I think that's the "Material ID" location inside the file.

> In #66709#738239, @jesterking wrote: > @e1412 Did you test importing the FBX and OBJ files back into Unreal? Do the material indices survive the roundtrip? > > From the files you linked to in https://blender.community/c/rightclickselect/4ydbbc/#5d2ed47dd3ac8b621cede009 I have a hard time seeing it could actually work, especially for the OBJ format, but also really for FBX. Hey, Nathan! It seems it doesn't survive the roundtrip indeed. Just exporting and reimporting to Unreal and the IDs are merged. But the thing is that 3DSMax is able to get that information from the FBX somehow. If only there was a way to export from Unreal in the ASCII format to check it :T Unreal just exports in FBX, maybe the OBJ doesn't support that "instanced" information. As I mentioned on the other link, I think it makes sense for the FBX to use this section for the IDs: LayerElementMaterial: 0 { Version: 101 Name: "" MappingInformationType: "ByPolygon" ReferenceInformationType: "IndexToDirect" Materials: *12 { a: 0,0,0,0,1,1,2,2,3,3,4,4 } } That cube has 12 triangles, so each of those numbers (from 0 to 4 - probably refering to the 5 materials applied (I said 6 by mistaken)) may be linked to the order of polygons inside the FBX. I think that's the "Material ID" location inside the file.

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Material ID instead of Materials in use #66709