No worries. I just threw a bunch of setups with overlapping, not overlapped and whatnot in there. None of it is really labeled in the scene so if you have any questions just let me know and I’ll explain what I did. 
Hey again,
sorry to bother you sir, but the downloaded project doesn’t seem to have anything inside it? Or do I need to import something?
Not a bother.
I just checked the download. It’s a zip file. I re-downloaded using the link and it’s showing the following:
I didn’t set the map as the default one, so if you’re able to see the project and files you just need to open the map labeled “Untitled.umap” in the content folder.
Let me know if that works.
Ah cool, I am using 4.6.1 - so I am going to download 4.7 and see if that allows me to open the asset (Says I can’t open it at present)
Thanks for all your help and patience with this! 
Oops! I didn’t realize I had started that one in 4.7. Meant to do it all in 4.6. The latest engine version is my default when launching. Glad it’s not a problem for you to download 4.7. You’ll find it to be an awesome version. Some cool changes and tons of new stuff (check out the release notes if you haven’t already).
Downloaded - I see that yours all seem to work - and in the examples where you haven’t removed the sides etc, the shadows are there to be seen - thankfully! I was beginning to lose my mind!
okay, so these seem to work from getting a quick look at them, I will get a much more in depth look over the coming days. Is it okay if I PM you if I have questions instead of spamming the forum? I am sure other people have more important issues than this, and are possibly working on something that is due for release soon, and I am still very much getting used to the engine.
We’re all friends here so no worries about spamming (at least with information that would be useful for any new UE devs, much like yourself). I don’t mind personal messages with regards to some things, but for a lot of things, especially if it’s helpful to anyone else out there, I’d like to keep it on the public space. I can speak from experience that often times in the past I’ve been a “lurker” on forums and would be disappointed if a topic never really resolved itself to some degree. I guarantee you that if you have these kinds of questions there are others out there that have them as well.
It’s taken a number of months to finally get around to getting this up, but Eric and I have been working on this in our spare time to help all the awesome new devs out there with basic lighting trouble shooting and tips that are some of the more common questions. You can see our progress here: A new, community-hosted Unreal Engine Wiki - Announcements - Epic Developer Community Forums
We’re continually adding to it and have a number of other examples to go as well. You can see the list of other examples that will be going up in my post here where I keep the status as updated as I can. This issue will be added to that list as well and if we run across some more I’ll add those in a fitting manner. Suggestions are always welcome too! 
Oh man, you are going to hate me!
So I just recreated the meshes from your example, in maya removing the sides, bottoms, adding corners etc - but my meshes are creating the shadowing effects! 
When I don’t use a “cornered” piece, and then set them adjacent (with no overlap) this is what happens along one wall (underneath)
Then I tried pushing an edge in, to get the 45 degree angle that you have in your meshes - this is the result :
I will add though, in both of these cases, the actual corner joins are beautiful now! If I could get the bottom to behave itself we could be onto something!!!
Thanks for all your help so far!
I am def doing something wrong - are you sure the lightmaps on the assets I posted up look okay? because I took the same approach when doing the new ones, but without sides, and it just simply doesn’t work. However, yours are fine, which leaves even more lost than I was before, I can’t work out why that ground shadow is happening so badly - and if I rotate it all the other way, the opposite happens - the weird corner shadow becomes a light in the corner of what is otherwise darkness (inverted of the picture above, essentially).
The thing here that needs to be taken into consideration is that from the looks of your last image you have a single floor plane that is rather massive. This will not have a good lightmap since it’s such a large surface with a smaller mesh covering it. Even increasing the LM to 2048 or 4096 would not yield good results with such a large surface in this instance.
Having a smaller room floor that better fits the room size will be more beneficial here. In my examples they can be better because of using the smaller floor mesh included with the starter content. The LM resolution for those was made to be 512 vs the 128 that was the wall resolution, if I remember correctly. The key here is to remember that the size of your mesh and the LM resolution go hand in hand.
Try using a smaller floor mesh and let me know what you find.
You sir… I owe you drinks!!!
Looking much better now :
I could probably imprive this furthermore by mapping the texture uvs better, then placing materials on the walls and floors to tidy up the last few little pieces.
Regarding the floor - are there faces I ought to remove like in the walls? or should that be a block? Bearing in mind that I will have multiple floors in various buildings.
Another update
I am seeing such good improvements - I think we can say that this is solved now for plain wall sections like this -
Over the next week or so, I will work on more complex wall shapes (extruding sections etc).
When I do a collection of say, 30 or 40 wall types that I think behave well, I will publish them to the forum for free use. Modular level building ought to be easier than it is, and pushing out a bunch of models so it doesn’t have to be done again and again by each developer is something I would consider standard practice.
Thanks for all of your help with this stuff.
Update pic so far - much cleaner with other materials added in :
Finally getting to a point where I can consider making more complicated meshes for this, and begin creating better texture maps so that I can put better materials on (Texture maps I actually have questions about, but will look around on the forums first)
Thanks again
This is awesome Leam and I’m sure the community will greatly appreciate this!
In theory it would seem so. In practice there is much more that needs to be considered, at least in my experience. The aspect of building modular pieces is the easy part. Having UVs that tile correctly and line up with other pieces, the lighting setup with lightmass, lightmaps and lightmap resolution, and using grid snapping. These are just some areas that can cause issues. There are others as well, but taking into account that all these different things can affect how your asset looks when snapped together can become frustrating to try and figure out until you have a solid understanding of how the systems all interact together and where to start breaking down the problem that needs to be addressed.
Assets that are not modular and have to work in conjunction directly with any other asset are much easier to figure out. But we’re all here to help out each other and learn in that process. The things you’ve learned and will continue to learn in this experience will hopefully carry over to others who read this post or those you directly help when you see them experiencing a hiccup in their approach.
This is always a fun stage when you want to start making something more complex and really have some fun! If you run into any questions or issues feel free to post and we’ll gladly help.
Feel free to message me with any updates. I know it sounds cliche and cheesy but I do like seeing people progress and to see the status of their work coming along. It’s always awesome to see what people are doing with the editor. Personally, I love to learn and help. My best approach to learning has been to help others with any their holdups and research ways to help them get around it.
I’ve been struggling with these issues for days now… I just can’t create the modular wall assets properly, I don’t even know what’s wrong with it anymore. I’m reading this thread over, and over, trying to find out what was I doing wrong…
Is there any step by step tutorial for this?
Not that I’m aware of, but feel free to post any questions or pics and I can offer some help where needed.
Okay, I’ll try to explain everything step by step, the best I can.
I have created a brand new project in UE4 just to make sure that no settings are messed up. I’m using engine ver 4.6.1.
Sorry for going so much into detail, but I’m at the point where I really have no idea how I can fix this, so I’m going to post a ton of useless screenshots.
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Model basic wall asset, no fancy edges.
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UVW Map:
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I also created a second UVW map, after reading something about creating a separate map in 3dsmax to work as a lightmap in UE4. That can be completely stupid, but like I said I’m kinda desperate to fix this.
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Exporting the selection as FBX file
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Importing the FBX by dragging & dropping it to the lib.
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Assigned some basic wall material.
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Lightning quality set to Production
Lightmap resolution: Default
Min lightmap resolution: Default
Image:
Lightmap resolution: 1024
Min lightmap resolution: 1024
Image:
Lightmap resolution: 1024
Min lightmap resolution: 1024
I am actually rather baffled by this.
first attempt: works rather fine, not sure what I did different.
As I said in the video, “Murphies Law”
I know my lightmaps stuff, I def. know my UV mapping stuff.
So I thought, lets make a video showing how to set up the uv’s, export the mesh, import it, rebuild lighting, and done.
It ended up being a 23 min. video trying all sorts of things to see what the issue might be.
The only thing that really seemed to help was to remove any of the polygons that are not visible by the player.
I do find it weird that a polygon that hidden between two meshes can cause these shadow-lines.
What I find even stranger is that this happens most with simple hard surfaces, as there are almost no seams left in the cave-stuff I have been making for the past 12 months.
I dont suggest most people to watch this, as its just me trying to get rid of that shadow-line, but perhaps one of the dev’s might find it amusing.
I will post up a few wall meshes at the end of the coming week with a project. Tim has helped me a lot and I think I know enough now to be able to help out as soon as I get the free time
Hey again…
I am working on meshes that I will redistribute to the community to help with modular level design.
One question I have is, what about the default tiling of the texture maps?
How large do you think I should make it in order for it to tile well with various materials?
Maybe there could be a BP approach taken here which would allow for materials to look good upon immediate use out of the box, rather than being massive etc?
Hey Luos - from what I can gather at this point, its that any solid face butted up against another solid face, will cause lighting simulation to occur differently than a “clean cut” might look.
I can only assume, that if there isn’t a face, its treated as seamless as long as all the edges line up - I am currently building a bunch of assets which I will be passing around the community for use. Just need the time to get them done.
Suggestions are welcome!