I love this subject! As usual, I think the answer is to do it optically if you want precision. When you do it metrically, it can create the optical illusion that a ball rolling through the gutter would get stuck on the curve, even though it wouldn't.
I was inspired by this tweet so I tried to implement a chrome button on iOS with UIKit, AV Foundation and Core Animation.
I was playing around with some blend modes and found a pretty interesting style. I would like to improve the surface texture more.