Hi PaQ,

re:
> I thought .lwo tag were more 'complex' than that.

Nope, it's just the same as smoothing groups. The only other thing is that if you have welding turned off it will have a separate part ID for each connected pieces.


> Here's a filleted cube example. If we talk about smoothing group, there isn't any right ?

If welding is turned on then there would be just one smoothing group (and one PartID in LWO) and all faces would be in that same group.

If welding is turned off then there would be a separate smoothing group/ PartID for each surface.


re:
> The issue here by using unwelded models is that I can't really refuse the vertex in case surfaces are
> overlapping (like an perfect array of cubes, all the shared surfaces will be merge together).

Why do they need to be merged?


> I have also attached the result .fbx from Houdini with the data stored under the name "id" (could
> be any name). However at this point I'm not really sure if .FBX can actually store custom attribute
> or if it's an Houdini shenanigans.

Hmmm, well I was looking through the FBX SDK briefly and I couldn't find anything that looked like "surface id" in there, so this may be some custom information that only Houdini is looking for.

I have a tool "FBX Explorer" that diagrams the info in an FBX file, but it can't load your example file. Is it possible to generate an older FBX version, like 2013?

- Michael