we had some discussions about it on vfx facebook group/vfx forums but sadly I havent find a properly way to do it in ue4.
Might be possible by combining a few flipbooks, some masking, others showing the spheres… but… no luck on my part.
Additional tweets showing cool tricks for it:
https://twitter.com/Gaeel/status/814751393542262784
additionally, i’ll forward this to someone from epic.
maybe he can shed some light, or well… substract some light on this matter.