UE4 and smoothing groups

I’m curious about UE and smoothing groups on imported meshes. I’m a total noob when it comes to 3D modelling for games. I’ve been using Hexagon and Cararra for modelling until just recently. In those applications you typically export your models to .obj files for import to any rendering software.

An .obj file does not contain any info or data on smoothing. You either export your mesh smoothed or not. The file format only contain polygons and that’s it.

I’ve just started learning 3DS Max to be able to properly export stuff to Unreal. I know very little about the .fbx file format. Other than it unlike .obj can contain pretty much any kind of 3D data, such as rigging, animations and cameras etc.

Now, before I got the hang of it, Unreal would warn me that my .fbx files didn’t contain any smoothing groups. And I’m curious of why it would even expect any kind of smoothing data. Does that mean that Unreal is somehow reading the lopoly version of the exported model and then apply it’s own smoothing modifier? Because, I’ve been making a habit of collapsing all smoothing modifiers before I export my models to .fbx. I mean, I want import the hipoly model in Unreal so it kind of makes sense that you then also export the hipoly mesh. Is that wrong? Or why is Unreal expecting to find smoothing groups when importing .fbx?

Smoothing groups are not the same as using a Smoothing Modifier!
A Smoothing Modifier generates new Polygons (via Subdivision)

A smoothing group is a set of Polygons that behave the same to lighting and reflections.
Polygon sets with different Smoothing Groups cause hard edges in lighting.

Here, every polygon has the same Smoothign Group:
Here, the same mesh with different Smoothing Groups:

In 3Ds Max, the Smoothing Groups are applied in the Editable Poly Modifier under the Face Selection.
When Exporting your mesh as FBX, you can select whether the Smoothing groups should be exported or not.

Thanks for the info!

.obj does contain smoothing information–however, most programs do not use the term smoothing groups, that’s more specific to 3ds Max, and I think it’s a bit easier to manage in 3ds Max.

For UE4, when you import something, it has the option to import smoothing from the file (if it has it) or it can try to generate its own smoothing. In 3ds Max you just have to make sure that you check the option to export smoothing in the FBX exporter.

Smoothing Groups via Maya 2017?

Also a newb here and seeking to make UE4 happy finding smoothing groups in my meshes. How can I provide for smoothing groups in Maya 2017? One source suggested I look for something along the lines of “soften normals” or “rounded normals”. I searched Help, tried RMB to select edges, then under Mesh Display select “soften edge”. Import into UE4 still returned the message that no smoothing groups information was found, mesh appeared blocky. Many thanks if someone here can clarify the workflow supporting smoothing groups through Maya 2017.