Right now, private areas are using the volumetric fog cubes and that's ok but despite using a kinda nifty graphic technique, it ends up looking distracting and cumbersome...
i propose that a better method would be letting the user draw out a rectangle on the table surface and that becomes the hidden area. a simple, flat card, colored according to the user color and maybe says "HIDDEN" or something... and basically, the entire volume above the rectangle is considered hidden with the upper bound extending to infinity... right now, the volumetric cuboid defines the upper bound of the volume too but that's pretty unnecessary isn't it? i don't think most people would use the hidden area up to 5 inches above the table to hide but then want to use 7 inches above it to reveal something - especially since we don't have hovering... everything falls to the table... so just make the rectangle define the borders within which nothing is rendered..