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 hack
    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, can be removed
    
    return y;
}