From 5d245d71515ac07923f7c4f58b09376dc12d6d01 Mon Sep 17 00:00:00 2001
From: Robin Engman <robinengman@hotmail.com>
Date: Tue, 11 Feb 2014 14:00:38 +0100
Subject: [PATCH] Added quaternion to angular axis in Math

---
 Code/OysterMath/OysterMath.cpp | 46 ++++++++++++++++++++++++++++++++++
 Code/OysterMath/OysterMath.h   |  6 +++++
 2 files changed, 52 insertions(+)

diff --git a/Code/OysterMath/OysterMath.cpp b/Code/OysterMath/OysterMath.cpp
index bbaccf11..7f7b1393 100644
--- a/Code/OysterMath/OysterMath.cpp
+++ b/Code/OysterMath/OysterMath.cpp
@@ -96,6 +96,52 @@ namespace Oyster { namespace Math3D
 	//	return ::LinearAlgebra3D::ExtractAngularAxis( orientationMatrix );
 	//}
 
+	Float4 QuaternionToAngularAxis(Float4 quaternion)
+	{
+		Float4 axis = Float4::null;
+		Float s = sqrtf(1 - quaternion.w*quaternion.w);
+
+		axis.w = 2*acos(quaternion.w*quaternion.w);
+
+		if(1 - quaternion.w > 0.001f)
+		{
+			axis.x = quaternion.x/s;
+			axis.y = quaternion.y/s;
+			axis.z = quaternion.z/s;
+		}
+		else
+		{
+			axis.x = quaternion.x;
+			axis.y = quaternion.y;
+			axis.z = quaternion.z;
+		}
+
+		return axis;
+	}
+
+	Float4 QuaternionToAngularAxis(Quaternion quaternion)
+	{
+		Float4 axis = Float4::null;
+		Float s = sqrtf(1 - quaternion.real*quaternion.real);
+
+		axis.w = 2*acos(quaternion.real*quaternion.real);
+
+		if(1 - quaternion.real > 0.001f)
+		{
+			axis.x = quaternion.imaginary.x/s;
+			axis.y = quaternion.imaginary.y/s;
+			axis.z = quaternion.imaginary.z/s;
+		}
+		else
+		{
+			axis.x = quaternion.imaginary.x;
+			axis.y = quaternion.imaginary.y;
+			axis.z = quaternion.imaginary.z;
+		}
+
+		return axis;
+	}
+
 	Float4x4 & TranslationMatrix( const Float3 &position, Float4x4 &targetMem )
 	{
 		return ::LinearAlgebra3D::TranslationMatrix( position, targetMem );
diff --git a/Code/OysterMath/OysterMath.h b/Code/OysterMath/OysterMath.h
index 23ee06db..6e8a66de 100644
--- a/Code/OysterMath/OysterMath.h
+++ b/Code/OysterMath/OysterMath.h
@@ -149,6 +149,12 @@ namespace Oyster { namespace Math3D //! Oyster's native math library specialized
 	////! Extracts the angularAxis from orientationMatrix
 	//Float4 ExtractAngularAxis( const Float4x4 &orientationMatrix );
 
+	//! Converts a quaternion as Float4 to angular axis as Float4
+	Float4 QuaternionToAngularAxis(Float4 quaternion);
+
+	//! Converts a quaternion to angular axis as Float4
+	Float4 QuaternionToAngularAxis(Quaternion quaternion);
+
 	//! Sets and returns targetMem to a translationMatrix with position as translation. 
 	Float4x4 & TranslationMatrix( const Float3 &position, Float4x4 &targetMem = Float4x4() );