The warning means that there is no smoothing group information saved in the fbx file. When the model was exported from Blender, the smoothing option was probably set to “Normals Only”, which will not export the smoothing info stored in the faces / edges. In this case, smoothing is not required, because the model was meant to be super blocky, with sharp looking edges. That’s why in this specific instance you can ignore the warning.
Now you may be wondering why it is displayed as a warning by default. Well, although in this case it was “meant” to be that way, not using smoothing at all is one of the many reasons that make the models look like computer-generated graphics and are also usually not visually pleasing. So under “normal circumstances” you would want to use some sort of smoothing.
The two most popular ways of adding smooth looking edges to models are:
- Using normal maps (you can bake a high poly model to a low poly one and use the resulting texture map to fake how the light interacts with the surface and add additional details not present in the actual low poly geometry mesh).
- Using smooth shading (that’s mainly what the warning is saying it’s missing from the fbx).
To use smooth shading, you could do this:
- Generally speaking, you want to use the mid poly technique if you want to use smooth shading only. It involves adding beveled edges with a very low amount of vertices.
- Right click on the model, select “Shade Smooth”.
- In the object data properties tab -> Normals section, make sure Auto Smooth is enabled.
There are tons of ways to control smooth shading and the normals, so this is far beyond the scope of this question, but you might want to look into it.
Here’s an example, the first picture is the model without bevels and smooth shading, the second one is with beveled edges and smooth shading via a data transfer modifier from a higher poly mesh.
- Export the model using the Geometry->Smoothing option set to Edge (or Face). I created a “UE4” Operator Presets so that I can recall those options quickly every time I export).
So if you try to import that model, which has been exported with the “Smoothing” set to “Edge”, there won’t be any warnings about missing smoothing group information.
