Fast Inverse Square root

inline float
FastInvSqrt( float x )
{
	float xHalf = 0.5f * x;
	int i = *(int*)&x;
	i = 0x5f3759df - (i>>1);
	x = *(float*)&i;
	x = x*(1.5f-xHalf*x*x); // 1st Newton iteration
	//x = x*(1.5f-xHalf*x*x); // 2nd Newton iteration
	return x;
}

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