Newton-Rapson Fast sqrt by Dranith

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float InvSqrt (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);     return x; }