If you look here you will see I am getting some bad lighting renders on my walls for example they are both the same texture however shade differently, how can I stop this from happening?
Also if you look at this image you will see I am left with black lines in my walls unless the lighting resolution is 256, anything lower and I get these black lines. I know this is probably down to lightmaps however no matter how I space the UV islands I’ll always get some sort of strange shadow on my walls. Is it okay to have the resolution at 256 or will it drain performance massively? Thanks any help would be super fantastisch!
This seems to be a common problem with the recent lightmass version…
Let’s hope they’ll fix it and in the meantime redesign your meshes or try your luck with LPV (light propagation volumes). 
Okay thanks, btw the person I am working with thought it would be funny to add those file names to the photos I have supplied sorry about them haha :o
I had similar issues when working with modular pieces (walls, roofs etc). I was also playing with different UV layout for light maps and it didn’t work. In my case, this issue was caused by pixel approximation (especially with low lightmap resolution) . When I used bigger lightmap resolution, the problem was solved or minimized.
When defining 2nd UV channel, You need to setup a proper grid spacing/size (1/your lightmap resolution) in your 3d application to ensure that lightmap will use correct pixels (shaded or illuminated). Remember to turn the snapping on. This will “tell” Unreal Engine to use exact pixel.
I plan to write a tutorial for this in the future.
Hi Nickmadd,
As and M.Orzelek has pointed out there are ways you can minimize it at the moment but not get rid of the issue all together. Hopefully this will be fixed in future releases. For now when building I would suggest having any edges meet at corners or use other objects to mask the seam.
World of Level Design has a great tutorial and basics of using Lightmaps](UDK - How to Fix Light and Shadow Lightmap Bleeding and Seams) as M.Orzelek described that would give you some great information. In their tutorials section on WoLD.com they have a few tutorials that cover nothing but Lightmaps and how to get the most out of them.
In your second image you point out “black lines” I see are not due to lightmaps there but rather that the middle wall is spaced back a little. It’s not directly flush with the ones on either side.
If you have any other questions feel free to let us know! 
Thank you!
Tim
