https://docs.blender.org/manual/en/4.0/scene_layout/object/editing/shading.html?utm_source=blender-4.0.2#
In Blender there are 3 shade options to render an object:
- Shade Flat
- Shade Smooth
- Shade Auto Smooth
The first option disconnects all the faces of the mesh and gives the facet normal to the vertex normal, so all the facets looks flat.
The second option gives to each vertex the average of the connected facets normals, so the mesh looks smooth.
The third option is an hybrid that disconnect all the faces of the mesh but compute an average normal for each vertex based on the angle between the connected facets. So if the angle between two facets is small the transition will be smooth otherwise it will be sharp.
This third option is not available in Babylon yet.
This playground shows how it could be applied in Babylon and what is the difference between the three options.