I’ve been working with a spotlight to create a street lamp casting light onto the road below. Whenever I adjust the settings for the spotlight, the lighting seems to work fine. Once I build the lighting, however, the spotlight loses its strength and the clean circular shape it projects onto the ground. See the comparison ima
ge (before/after build lighting)
Yes, is it just one mesh with the tiled road texture. (btw I’m quite new to UE4)
That seems to have worked, thanks for your help! 
I think it’s the lightmap on your road ( the payment looks ok ). Is that one big mesh?
Ah. So you need a light map resolution of approximately infinity
Try putting a short chunk of road under the light and build again.
Once you’ve split it into chunks you might get problems with discrepancies at the boundaries, but that can be dealt with by tweaking lightmass settings.
( TBH I can’t recall what, but Makigirl has answered the question about 500 times ).
