Hardly "modern", but here's a description of the graphical design of The Sims pie menus [1] that I impemented in 1999 and wrote up in 2001:

The classic papers on transparent user interfaces include Toolglass and Magic Lenses: The See-Through Interface (1993) [2], and A Taxonomy of See-Through Tools (1994) [3].
The pie menus in The Sims [4] use a combination of desaturation, darkening, and alpha blending to feather the edges of the menu.

Why transparency and the other effects? I didn't want the pie menus to obscure too much of the scene behind them. You can see through the pie menu as the animation continues on in real time behind it. The head of the currently selected person is drawn in the center of the pie menu, and follows the cursor by looking at the currently selected item.

I found it necessary to somehow separate the head from the rest of the scene, otherwise it looked like a giant head was floating in a room of the house! Drawing a solid opaque menu background would obscure too much of the scene. But even a partially transparent menu background still did not visually separate the head from the background scene enough. It looked muddy and cluttered, instead of crisp and bright.

So instead of simply alpha blending, I actually made it desaturate the background (removes the color so it's gray scale), and darken it (like casting a colorless shadow).

I wanted the colorful head to look sharp and bright up against the dark gray background. So the effect looks at the Z buffer to clip out the head in the menu center, so it remains bright and colorful against the dark gray background. That gives it visual "pop" that separates the head from the background. The edges of the effect are feathered, so there's no sharp line dividing the inside and the outside of the menu (useless visual clutter).

The gray shadow just gradually tapers off with distance, suggesting that the pie menu active area extends to the edge of the screen, not confined to the borders of a circle. The labels are drawn with high contrast drop shadows around the pie menu, so they stand out and easy to read, partially overlapping the shadow so they're look like they're part of the menu.

There's special code to perform that particular combination of pixel filters in real time, to every frame just after the 3D rendering phase.

The pixelated censorship effect works the same way as the pie menu shadow, like a Photoshop filter run after the 3D rendering phase. There's a special suit type that's tagged as a "censorship" suit. It consists of bounding boxes attached to the varius bones of the skeleton that you can select to censor. So if you just want to censor the head, you attach the head censor suit to the head bone. The 3D character renderer transforms the 8 vertices but doesn't draw anything, and stashes the screen bounding box away for the pixelation filter to draw later. That's how it can censor just the crotch of naked men, but also the chests of naked girls gone wild.

[1] https://www.youtube.com/watch?v=-exdu4ETscs

[2] https://research.tableau.com/sites/default/files/1993-Toolgl...

[3] http://www.billbuxton.com/TGtaxonomy.html

[4] http://www.tsomania.net/assets/images/gameguides/sprinklers_...