From b63ce0dee9c722a0f541d1cefb00691a46a1cb94 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Tue, 11 Sep 2007 17:08:06 +0000
Subject: [PATCH] From Art Tevs, Added log2 function.

---
 include/osg/Math | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/osg/Math b/include/osg/Math
index 7ceca75d2..6128dc9e8 100644
--- a/include/osg/Math
+++ b/include/osg/Math
@@ -114,6 +114,9 @@ namespace osg {
 const double PI   = 3.14159265358979323846;
 const double PI_2 = 1.57079632679489661923;
 const double PI_4 = 0.78539816339744830962;
+const double LN_2 = 0.69314718055994530942;
+const double INVLN_2 = 1.0 / LN_2;
+
 
 /** return the minimum of two values, equivalent to std::min.
   * std::min not used because of STL implementation under IRIX not
@@ -191,6 +194,10 @@ inline double RadiansToDegrees(double angle) { return angle*180.0/PI; }
 inline float round(float v) { return v>=0.0f?floorf(v+0.5f):ceilf(v-0.5f); }
 inline double round(double v) { return v>=0.0?floor(v+0.5):ceil(v-0.5); }
 
+inline float log2(float v) { return static_cast<float>(log(v)) * INVLN_2; }
+inline double log2(double v) { return static_cast<double>(log(v)) * INVLN_2; }
+inline int log2(int v) { return static_cast<int>(floorf(log(v) * INVLN_2)); }
+
 #if defined(WIN32) && !defined(__CYGWIN__) && !defined(__MWERKS__)
     inline bool isNaN(float v) { return _isnan(v)!=0; }
     inline bool isNaN(double v) { return _isnan(v)!=0; }