How to fade out material applied on geometric brush actor

Hello everyone,

is there a simple way to fade out a material applied to a static geometric brush actor? So far I tried the DepthFade node connected to the Opacity but that does not do the trick for me. Basically I want the Material - or the brush actor (floor) itself - fade out on the edges so I can get rid of the hard lines and get a smooth transparent fade.

For a better understanding I’ve uploaded my current Material, the current state and how it should look like.

thanks so much!