From FumeFX to in-game effect
The workflow is actually fairly involved: the explosion was originally simulated in 3ds Max using FumeFX, and the geometry imported into Unreal Engine 4 via the FBX format.
The explosion is also rendered inside 3ds Max as a series of 2D cross-sections.
The resulting renders are then used within Unreal Engine 4 as textures, with Unreal automatically interpolating between them to recreate the missing parts of the original texture volume.
To reduce the processor hit, instead of raytracing the explosion, the animated textures are used to drive the colour values of a static GPU particle cloud, creating the illusion that the explosion is passing through it.
Phew. Still, as the video observes, it’s a more realistic alternative to sprite-based effects.