Unreal Engine 4.18 has been released with the most prominent feature being Volumetric Lightmaps and multi-bounce indirect lighting from Skylights. Unfortunately the new features in 4.18 can’t be used by content developers for UT4 since UT4 is several engine revisions behind at this point. Hopefully that will be remedied soon.
From the Unreal Engine site:
Volumetric Lightmaps store precomputed lighting at all points in space by covering the entire Lightmass Importance Volume with 4x4x4 bricks of lighting samples. Bricks are placed with higher density near static geometry, where indirect lighting is changing the most. This data structure allows efficient interpolation of indirect lighting to any point in space on the GPU. The Volumetric Lightmap is interpolated to each pixel instead of once for the whole component and has more reliable detail than our previous Indirect Lighting Cache method, resulting in fewer cases of light leaking.
Go HERE for all of the details on the 4.18 release.