Vutils

include/Vutils.h

@@ -218,6 +218,7 @@ bool vuapi use_std_io_console_window();
 bool vuapi is_flag_on(ulongptr flags, ulongptr flag);
 intptr vuapi gcd(ulongptr count, ...); // UCLN
 intptr vuapi lcm(ulongptr count, ...); // BCNN
+float vuapi fast_sqrtf(const float number); // Estimates the square root of a 32-bit floating-point number (from Quake III Arena)
 void vuapi hex_dump(const void* data, int size);
 
 #include "template/math.tpl"

src/details/math.cpp

@@ -105,4 +105,27 @@ intptr vuapi lcm(ulongptr count, ...) // Least Common Multiples -> UCLN = | a1 *
   return result;
 }
 
+// https://en.wikipedia.org/wiki/Fast_inverse_square_root#Overview_of_the_code
+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;
+}
+
+float vuapi fast_sqrtf(const float number)
+{
+  return 1.F / q_rsqrt(number);
+}
+
 } // namespace vu