Yeah, it wasn’t a real mystery (as noted in the Wikipedia article, it already existed in the numerical literature). But practically it would have surprised a lot of programmers in the days before Wikipedia, when you’d have had to read a somewhat specialized textbook or a paper to learn about it.
Plus the exact constant selected and the method used to derive it remains a minor mystery, right? In the sense that it is good but non-optimal.
https://en.wikipedia.org/wiki/Fast_inverse_square_root for those who just want the info without AI filler
It's not a mystery per se.
It's explained exceptionally well here [0].
[0] https://youtu.be/p8u_k2LIZyo?si=loEDS5hPcRGWXk0E
Yeah, it wasn’t a real mystery (as noted in the Wikipedia article, it already existed in the numerical literature). But practically it would have surprised a lot of programmers in the days before Wikipedia, when you’d have had to read a somewhat specialized textbook or a paper to learn about it.
Plus the exact constant selected and the method used to derive it remains a minor mystery, right? In the sense that it is good but non-optimal.
The "mystery" being referred to in the title is how the magic number was derived. This is what most of the article talks about.
Calling it a "mystery" gets suckers like me to click the link.
Ignore the clickbait aspect. It is one of the craziest flexes in game development.
The guy had made Doom (nice fast pseudo 3D), Quake (fast 3D), and now made it look great.
Finding obscure math and figuring out that it was the correct fit for his renderer is just so bonkers.
The wikipedia article gives a lot more detail and history than this fluff piece:
https://en.wikipedia.org/wiki/Fast_inverse_square_root
This could have been a good article except for all the AI slop. The future is bleak.