Nice that Rein didn't cop out and embed images. I'm a little surprised that adding arbitrary closed outlines to PostScript output was the most straightforward way to do it. I would think you could algorithmically mask out a portion of an ideal ring (because the cup wasn't resting flat and saturation across the rim wasn't even).

I also didn't realize until now that DVI can only natively encode characters and aligned rectangles in black, and that's why so much TeX work requires PostScript support downstream.