The Nvidia VXGI build, as a representative from Nvidia said earlier in this massive thread if I recall correctly, is free for anyone using the UE4 to use (someone feel free to correct me if I’m wrong, hunting for the exact quote in 78 pages would take all night). It wasn’t Alexey who said it, it was someone else from Nvidia and the name slips my mind at the moment so I can’t search for it.
As for VXGI being pretty heavy on performance, it can be. Fortunately, it can get a lot better.
r.VXGI.mapsize = 32 (this will make the voxels much, much larger and decrease the amount of vram it uses)
Then in post processing, set sparse tracing to 4 and cones to 4. There may be other ways to make it a bit cheaper, but generally those are the most important ones. VXGI specular I actually find with these settings has a minimal, almost negligible performance impact on things, so you’re probably safe leaving that on.
For my personal rig, which is using the 3GB GTX 780, it’s possible to make VXGI have the same performance hit LPVs have. On anything past that, Maxwell and soon Pascal, it has even less of an impact since VXGI is properly hardware accelerated.