Can anyone help me with my problem ? Tried some solutions but seems like none of them worked, I have this issue for a long time.
You can’t make that all in one mesh, it can only use one lightmap per mesh so for that whole surface it only has a single lightmap and there’s not enough detail.
Instead, first separate into meshes by different materials, then consider the total surface area of those meshes and consider whether you need to split them up further. You can make things like walls into a separate mesh from the ceiling and floor. If that’s still not enough detail then you can further split things up on the corners.
Thanks you so much !