Hi there I started recently following tutorial about lightmap and decided to create my own assets. For some reason I can see little crease at the edge of the object like when you snap one onto another.
I tried increasing lightmap resolution didn’t work, neither indirect light quality or lighting smoothness. I have exactly followed the principle from World of Level Design but I cannot pin it down the problem.
this also applies to my other mesh but i assure you I have spent so much time on lightmap knowing where light and shadow going to hit. Can anyone help me how to get rid of this little crease cause? Spent
time adjusting UV lightmap and no luck 
I believe your not supposed to have your uv lightmaps at the edge otherwise it can bleed. your uv lightmap should have a few pixels of border is my understanding. Although im not sure if thats is the cause of your problems
First off, you have too many UV seams, you don’t need to split up the mesh like that, many of the polygons can be connected together. Otherwise you need a higher resolution lightmap for those thin polygons.
The seam is because of the separate meshes, lightmass processes meshes separately, so if you have a flat surface then the lightmap doesn’t get smoothed across the meshes.
Those shell near border not causing me the issues but where you see the hard edges is near those between shell.
Like said this applies to all my mesh but even if UVs aren’t near the border, I wonder if it’s UE4 am missing something. Oh, Im using 4.8 btw 
Hi again, I have I did manage to resort the UV, but I still have the same issues
Try have the entire wall as a single mesh.
Because of what “darthviper107” said, that being, “the seam is because of the separate meshes, lightmass processes meshes separately, so if you have a flat surface then the lightmap doesn’t get smoothed across the meshes”.
I see what you mean, I will give it a try.