Fast inverse square root
Algoritmo de la raíz cuadrada inversa rápida
- Date
- c. 1999 · confidence low
- Place
- Mesquite, Texas, United States
- Credited to
- Gary Tarolli, Michael Abrash y John Carmack
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What it is
Algorithm that quickly approximates the inverse square root of a floating-point number through a bit-level manipulation, widely used in 3D graphics for its speed over conventional methods.
The exact origin and authorship are disputed: it is credited to several people (Gary Tarolli, Greg Walsh, among others) before becoming widely known through Quake III Arena (1999).
What it led to
- Faster lighting and normal-vector calculations in 3D video games
- Popularization of bit-manipulation tricks in programming
- Later study and documentation of the algorithm (the 'magic constant' 0x5F3759DF)
- Influence on real-time numerical approximation techniques