Hello Michael,

So here's a 2013 version. I don't think there is indeed a specific attribute name like "surface_id" supposed to be used for that purpose.
However I just came across this example (maya to unity) where custom attribute is created and stored in .FBX file (even animated in this example) ... so it's not completely odd to store additional information with that format.
https://www.techarthub.com/how-to-import-custom-properties-from-maya-into-unity/

Having vertex merged is kinda useful to actually exploit "true" connectivity, like assigning materials or groups. In many polygon modeler it's common to simply double click on a polygon to select the whole connected mesh ... like a bunch of bolts that doesn't have any group/name set yet, you can just double click on them and tag them.
With the "unweld" options I have tons of individual surfaces (on purpose), very handy for uv'ing, but not so much for 'normal' selection work.

Hi PaQ, thanks for the 2013 version .fbx, the "FBX Explorer" app is able to load that one ok.

Looking through there I see some chunks of data for Material, Normal, UV, and "UserData 0" and "UserData 1". So presumably one of the user data chunks is for the surface ID values.

Do you know if there is any documentation on how Houdini is expecting the surface ID user data to be structured?

Thanks,
- Michael

Hello Michael,

Thanks a lot to looking at this already !
I didn't find any doc about that subject, however maybe I did something wrong on my side previously, but the ASCII version works too now (maybe by switching to .FBX 2013).
Here's a simple cube example where I did assign a custom 'id' and saved as .FBX 2013 ASCII. I can see in a text editor the 'LayerElementUserData', describe as such :


LayerElementUserData: 1 {
Version: 101
Name: "UserDataLayer1"
MappingInformationType: "ByPolygon"
ReferenceInformationType: "Direct"
UserDataId: 1
UserDataArray: {
UserDataType: "Integer"
UserDataName: "id"
UserData: *6 {
a: 0,1,2,3,4,5
}
}
}

Hi PaQ, can you please test this file to see if Houdini recognizes the surface id data that I've put in it?

- MIchael

Hello Michael, that's perfect !!!! Thank you so much !