From 557900d1b277a315372151e1ef29ea1398537e6c Mon Sep 17 00:00:00 2001
From: Valmar33 <Valmar33@users.noreply.github.com>
Date: Sun, 29 May 2016 05:14:57 +1000
Subject: [PATCH] Revert "Revert "Added HMM_FastInverseSquareRoot function""

---
 HandmadeMath.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/HandmadeMath.h b/HandmadeMath.h
index 912b2ad..7f54423 100644
--- a/HandmadeMath.h
+++ b/HandmadeMath.h
@@ -223,6 +223,7 @@ HMMDEF float HMM_ToRadians(float Degrees);
 HMMDEF float HMM_Inner(hmm_vec3 A, hmm_vec3 B);
 HMMDEF float HMM_SquareRoot(float Float);
 HMMDEF float HMM_LengthSquareRoot(hmm_vec3 A);
+HMMDEF float HMM_FastInverseSquareRoot(float Number);
 HMMDEF float HMM_Length(hmm_vec3 A);    
 HMMDEF float HMM_Power(float Base, int Exponent);
 HMMDEF float HMM_Clamp(float Min, float Value, float Max);
@@ -351,6 +352,24 @@ HMM_LengthSquareRoot(hmm_vec3 A)
     return (Result);
 }
 
+HINLINE float
+HMM_FastInverseSquareRoot(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 ) );
+
+    return ( y );
+}
+
 HINLINE float
 HMM_Length(hmm_vec3 A)
 {