float InvSqrt(float x)
{
float xhalf = 0.5f*x;
int i = *(int*)&x; // get bits for floating value
i = 0x5f3759df - (i>>1); // gives initial guess y0 （神奇的数字！）
x = *(float*)&i; // convert bits back to float
x = x*(1.5f-xhalf*x*x); // Newton step, repeating increases accuracy
return x;
}
{
float xhalf = 0.5f*x;
int i = *(int*)&x; // get bits for floating value
i = 0x5f3759df - (i>>1); // gives initial guess y0 （神奇的数字！）
x = *(float*)&i; // convert bits back to float
x = x*(1.5f-xhalf*x*x); // Newton step, repeating increases accuracy
return x;
}
