It looks fine until I bake the lighting, leading me to believe my UVW unwrapping sucks. (basic flatten mapping)
Mind posting the OBJ or FBX file? A simple unwrap isn’t going to give you good results with the lightmap. Even with a perfect unwrap, a mesh like that bench would need a very light light map resolution, probably 1024 or maybe 2048, just because of how many pieces there are. I could try creating a similar mesh, but that would take a lot more time.
For unwrapping you need to make sure you have no overlapping faces, that each face is getting enough space on the texture, and that the islands aren’t heavily deformed.
No problems! Knock yourself out. I know the islands are way to small for the map, I’m just unsure which way to go with it.
Also, increasing the lightmap res helped one of the benches - but it wasn’t perfect. Meaning, the colours were a little off.
https://www.dropbox.com/s/6xrzzb5ky7akxv0/odesd2_B1.fbx?dl=0
https://www.dropbox.com/s/4geylwas7ekpjjz/odesd2_B2.fbx?dl=0
Looking at your first object, it is clear that you will need quite a high LM resolution but furthermore, your objects contains sooo many unncessary polygons. Problem is that you modelled in the cuts on sub-object but just sticking solid pieces into each other would result in the same visual appearance but a lot less faces. I would either go remodel it or at least delete all the hidden faces so that you get space in your LM for the important , visible parts.
Looking at the model, you could maybe also get rid of the chamfers because they are very small + if you have them set to hard edges, in order to get a good LM, you will have to have seams at those hard edges of your model.
Getting rid of those and closing all the unnecessary holes, your model and UV will look like this (copy of the exploded model on the right so you see what i mean by closing holes and sticking them together):
You can also do it this way with the least number of splits
I would also reduce the polygon count, you probably don’t need so many segments for the curves.
Ok great! I didn’t model these btw. They were downloaded. I’m assuming these models are aimed at people doing Architectural visualisation (like myself), so Hi-Poly models are pretty normal.
So if I understand you correctly, you deleted the items that weren’t necessary to the model and kept everything else that was?
Yep. And did a flatten mapping afterwards, you could def. get away with a better unwrap there if you weld a few seams (maybe better not weld hard edges, but the circumferential faces for examples)
But you could also remodel it, depending on what you are faster at.
If you test build with low lightmass settings and preview quality, it’s not going to look great either!!!
I took OP’s original FBX and used a 256x256 lightmap but high quality lightmass settings. Not THAT bad. At 512 it’s pretty much artifacts-free. Add your real material and it shouldn’t be noticeable. Optimize a little bit your lightmap and it’s going to be perfect.
My lightmass settings were, scale .15, bounces 30, quality 4, smoothness 1 (uncompressed lightmap and production quality)
Agreed. I’ve read people have more problems than not if they test below "medium"quality, so that tends to be what I stick with for testing purposes.
Correct me if I’m wrong, but wouldn’t 2-4 lower res meshes (256-512) add up to about 1024-2048 res anyway?
Cool. I’ll give it a good crack tonight and see how I go. Thanks for your help.
If you like to go for quality than there is one option left, pixel perfect UV Shells… It’s a hell of work but you will get the most perfect lightmaps that are possible in UE4.
First of all i would simplyfy the mesh, you wont recognize any difference in UE4 “quality” Picture 1. Than do the pixel perfect unwarpping, again it’s hell ! 
I unwrapped just one board
to show you what i mean. Last point is, make sure you are using the right smoothing groups for your mesh.
You can’t do that on rounded meshes, you’ll get some messed up lightmaps because of stretching if you try to make a curved polygon rectangular.
Thats not true, just try it. First of all the mesh it not full round and even when it is, it worked always just fine for me. In fact i had always light map bleeding with round meshes, after i swiched the lightmap UV’s to squares the lightmap issues disappeared.
@Adik, as seen in your screenshot, you get mainly artifacts on the chamfered edges, so yeah he could optimize it + i thought closing the holes was clear in my screenshot but thanks for confirming my approach 
and in general i am with Adik here, you especally in comparison to your unwrap, darthviper, it will look better because you welded hard edges in your uv map and thus will have bleeding, so you would need quite a high resolution for your unwrap in comparison to get your chamfer edges clean (which i deleted for comfort:D ). But od course there is no ONE solution. 
Here is a simple sample where i used a Cylinder but the lightmap UV shells are “square” pixelperfect. You get no artifacts by not keeping the form of your mesh for the lightmaps. What you get by keeping your shells square and pixelperfect is more space and “almost” perfect lightmaps.
Cylinder with chamfared edges, lightmap resolution is set to standard 64
UV Shells for the cylinder with chamfered edges:
Lightmap resolution is standard: 64
@Adik, can you bake that same object with a series of bars above it, something like this ||||||, I want to see if the shadows have artifacts.
This is what happens:
You can’t fit a round shape into a rectangular shape without warping
Just for the lightmaps not for your textures, have a lock above, for lightmaps it is working just fine. Of course you can’t unwrap your UV’s like i did for your main textures, this wont work and look weird like on your picture above.
@ZacD what do you mean by bars ?
Here is another sample… And the lightmaps are still on cheap 64 x 64
Depends on the shadows that it receives, lightmap pixels will line up the same way so if there’s any lightmap detail then it’s going to look wrong. For instance there’s an edge on there that’s really sharp because it’s getting warped.