Ein Vortrag von Sebastian Ritterbusch auf der GPN20.
https://github.com/id-Software/Quake-III-Arena/blob/master/code/game/q_math.c
/* Copyright (C) 1999-2005 Id Software, Inc., GPLv2 */
float Q_rsqrt( float number ) { long i; float x2, y; const float threehalfs = 1.5F;
x2 = number * 0.5F; y = number; i = * ( long * ) &y; // evil floating point bit level hacking i = 0x5f3759df - ( i >> 1 ); // what the fuck? y = * ( float * ) &i; y = y * ( threehalfs - ( x2 * y * y ) ); // 1st iteration // y = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removed
return y; }