There are a couple of threads on it here on the forums.
This one is UE4 & Houdini specific:
But people have done this with 3ds max or Maya for Unity as well.
Here’s one done in Max:
Like I said, Realtime VFX is the group that uses whatever tools it needs to get the results needed. If you look at Blizzard effects for example, you’ll see a lot of things that you might expect to fall under the animation department being used in their effects. Some of the stuff in the original World of Warcraft was simply pre-animated and not using any in-game particle system. The original Unreal game did some particle effects as baked out animations too.