i = 0x5f3759df - ( i >> 1 ); // what the fuck?

反平方根快速演算法 Fast inverse square root

簡單啲嚟講，為咗計算速度，犧牲少少精確度

就會出咗咁嘅嘢出嚟
0x5f3759df - ( i >> 1 );

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;
}

https://en.m.wikipedia.org/wiki/Fast_inverse_square_root


不過識依啲冇乜用，當冷知識知道下都幾好

留名學嘢

好似見過

撞post
?

hi

ALPHA BB