Faceted Shading After Import
Smooth mesh looks flat-shaded in the engine
Also known as: Hard edges in Unreal · Smooth shading lost after FBX import · Import normals · Smoothing groups missing
Quick answer
A smooth model looks faceted or blocky after import when the engine did not receive its smoothing information. Export smoothing from your 3D tool (in Blender's FBX exporter set Smoothing to Face or Normals Only), and in Unreal's import options choose Import Normals so the engine keeps your normals instead of computing its own. If a mesh is smooth in the 3D tool but flat in the engine, this is almost always the cause.
How to fix it
Set hard and soft edges deliberately before export, then re-import and compare the model with the viewport. Weighted and custom normals travel in the file as normals, so import them rather than recomputing. If a baked normal map shows black or uneven shading, check the tangent basis too: use the same tangent calculation for baking and rendering, such as MikkTSpace, where your tools offer it.
