Lighting is weird on the edges of my modular building blocks
I have had this problem a while now, when I place 2 or more exact same meshes next to each other(they are tiling) and I built lighting it looks like this:
That is a stationary light with shadows.
Why does it does that? The only fix I found so far is merging the meshes into one, but that is suboptimal and I rather not do it.
The things that I have tried are the following:
Not sure how applicable this guide is to UE4, but following the principle of not putting UV borders between pixels coupled with adjusting indirect lighting smoothing, I was able to minimize the issue, referenced in the question, to the point where it is was almost unnoticeable.
Do note, that you should mind size of your lightmap in a such way, that lightmap UV seams never fall in between pixels. Roughly estimate intended lightmap size for particular object, 64x64, for example and unwrap it using pixel snapping. Grid step for this would be 1/64=0.015625. Then, if you want to adjust lightmap resolution in the engine, you can do so via power of two value, and your snapping will preserve for higher or lower lightmap resolution. And always leave some sort of padding for your lightmap unwrap, not only between UV shells, but also UV islands and 0-1 borders.
If you don't want to bother with this precision during unwrap, or if you are still getting noticable seam, consider hiding it under some sort of trim geometry, or plan your modular kit so that border faces join always at some sort of angle.
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