However, I simply can’t get it to function properly. I am using this blueprint and as far as I understand, I need to link my effect to ‘SphereCenter’ but it simply stays black no matter what I do and similarly, the outside stays in gray mist.
You half way there, what you made is a mask and with that you can swap between 2 different post processing effects (or mask single effect) using Lerp node and it’s Alpha pin, so you alter between A and B, or use it anywhere else
The way post processing material works is that you can sample screen pixels (as well as some other data in GBuffors, like outputs of other material on screen, roughtness etc.) like texture and alter it, you sample color using SceneTexture in PostProcessInput0, place Denaturation, plug Color to main pin of Desaturation and plug your mask to OneMinus (since more value is closer to 1 the more desaturated it becomes) and then plug it to Fraction, and thats it.
You probably would figure this one yourself if you knew about Post Process material and what you got on screen and think a little how you would use it to achieve the same result. So read about post process material:
