Thanks for answer heartlessphil. Yes I know BSP works opposite. I tried connecting meshes with BSPs in other project, but i didn’t like it cause the BSP was somehow more blueish, so now i do all visible parts in Blender. After difficulties with UV maps for lightmaps this time all the walls are separate meshes - with only one island per mesh. Tell me what should be the distance of isle to the border of UV map? I have used .3 in blender tho i don’t know is it enough but i thought that resolution of 512 would solve any issues. 
I’ll prepare UV maps screens now. Thanks again.
I from here to make highrise image,
just change the numbers, 1 is small, 10 is large size and render very slowly.
So, You were right I think. There is some third, red, I think auto-generated UVmap, but the lightmap coordinate is set to 2, and channel 2 looks good when excluding the border proximity. the problem might be somewhere else, ie. black boxes too thin, or not aligned with the UE4 grid? Does it matter?
uff, it ptompt me ‘database error’ all the time
Try to check “use two side lighting” ?
I think there is not enough space on the contour of your lightmap (CH2). It’s too flush… Use CH1 for your lightmap instead, it looks better. Check the static mesh options on the right panel, you’ll find ‘‘lightmap coordinate index’’…set it to 1 for channel 1.
This is well know method and I tried it myself but felt it was not that good comparing to the matinee output with all filters applied at game level.
I agree with , I tried taking a screenshot (print screen) from a camera with resolution set to 4k in game and it’s the best results I’ve gotten so far. The high res screenshot just seems to produce a huge amount of Aliasing and even weird artifact. It’s almost like if half of the game graphical features are turned off while the screenshot is being taken. lol.
This is my new screenshot workflow, of course, the resolution is upscaled to 4k in-game but in reality I get a 1920x1080 image…There is very little aliasing tho, which is great!
I launch the game with these settings, wait a few seconds for AA to stabilize and press print screen. Then copy it in photoshop.
Thanks guys for advises. I have upgraded to 4.8 and started over, this time i have unchecked ‘generate lightmaps’ and it is better. 4.8 is mush faster, results are better, so it was half of the solution;)
About ‘use two sided lighting’ i tried it, red the docs, and it seems to work well but only with static lights, what is not an issue for me at the moment. That made no need for ‘black boxes’ around all to prevent color bleeding, only ‘outer shell’ mesh. So again: ‘use two sided lighting’ works with static lights only. Docs stated that for other lights one may make the material two-sided in the material editor details panel, but when i did it there was still a little sun disk reflection visible on the floors, so - no. Now almost all is ok, tho i get strange reflections, i can still see clouds reflection in tv. Please don’t mind design as it is very early WIP. I love the performance of UE4, ability to realtime render is just jump to the future, but sometimes I loose so many time on the stuff i wouldn’t have any issues in ‘traditional’ rendering software. The render time advantage exceeds all the disadvantages tho. Nevertheless i’ll carry on, hope will not have to start over after I finish because of that strange outside reflection.
By the way, what should be the border, countour size of LM UVmap?
it was just lack of reflection shadow box.