4 ms·

How can you write an article on rounded corners without mentioning Steve Jobs and Bill Atkinson? https://www.folklore.org/StoryView.py?story=Round_Rects_Are_Ev

• PaulDavisThe1st 5y ago
  I'm "old", but I know that not every article about X has to be full history of X.
  • perilunar 5y ago
    Well sure, but the first sentence of the article is practically the title of Andy Hertzfeld's post. It would have been perfect for a link at least.
• JKCalhoun 5y ago
  I was expecting the same. I don't agree with a lot of what Jobs did, but he was absolutely right about rounded rectangles. > Bill's technique used the fact the sum of a sequence of odd numbers is always the next perfect square (For example, 1 + 3 = 4, 1 + 3 + 5 = 9, 1 + 3 + 5 + 7 = 16, etc). So he could figure out when to bump the dependent coordinate value by iterating in a loop until a threshold was exceeded. This allowed QuickDraw to draw ovals very quickly. Still blows my mind. I have a hankering to try to blind-rewrite this algorithm knowing only the above.
  • bobbylarrybobby 5y ago
    Were square roots really so slow that integer addition in a loop was faster??
    • the2and7 5y ago
      68000 processor on the Mac didn't support floating point operations.
    • dahfizz 5y ago
      I wouldn't be surprised if that is still the case. Rule of thumb is that sqrt is on the order of 10x as expensive as integer addition, though this obviously depends on a lot of factors.
  • unnah 5y ago
    That would be a variant of Bresenham's circle algorithm: https://en.wikipedia.org/wiki/Midpoint_circle_algorithm https://en.wikipedia.org/wiki/Midpoint_circle_algorithm Certainly a fun exercise...