Fast Inverse Square Root Algorithm 🧮

In this video we will take an in depth look at the fast inverse square root and see where the mysterious number 0x5f3759df comes from. This algorithm became famous after id Software open sourced the engine for Quake III. On the way we will also learn about floating point numbers and newton's method.

0:00 Introduction
1:23 Why Care?
3:21 The Code
4:18 IEEE 754
9:38 Bits and Numbers
12:09 1st Step: Evil Bit Hack
14:46 2nd Step: WTF
17:34 3rd Step: Newton
19:46 Summary

Picture of John Carmack is licensed under CC BY 2.0 from author Drew "Prognar" Campbell.
Source: http://flic.kr/p/6YxWYp