First thing I want you guys to know is that I am not doing this for the first time… I have done a portfolio on unreal before very successfully. The portfolio was to have an interior scene for android mobile devices. Have done the scene with the same method…
Now the problem is that I am having issue with lightmap on the walls are appearing dirty. The wall has smooth shading(vertex normal) on it with normal map that works fine in blender. And on top of that I have imported other object with similar properties that are working fine… note : that is project (actual scene) was integrated from blenders previous version to this new one (2.82 to 2.9 to 2.91) and the assets was just created in blender 2.91… Now I know the lightmap resolution and all the settings for lightmap baking, as I said I am familiar with the unreal engine. and I know how to export using blender… no uv map or other problems are there… All I can see is normal problem… somehow unreal is screwing the normal data or something else… IDK. Please help