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Aerofoil/notes.txt
2019-11-11 00:11:59 -05:00

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QuickDraw oval/rect drawing:
https://www.folklore.org/StoryView.py?story=Round_Rects_Are_Everywhere.txt
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.