How do the devs of anime vanguards get this effect in a gui


im wondering how the devs of anime vanguards get the effect behind the character like in this screenshot because you cant have particles in a viewport frame. I want to make an effect similair to this.

Using math, they are showing the effect on client and with some calculations they show the effect right Infront of the camera. (Example: Copy the VFX and parent it to workspace and set its position Infront of the camera)