Merge branch 'master' into nazara-next

include/Nazara/Math/Quaternion.hpp

@@ -60,6 +60,7 @@ namespace Nz
 
 			T SquaredMagnitude() const;
 
+			RadianAngle<T> To2DAngle() const;
 			EulerAngles<T> ToEulerAngles() const;
 			//Matrix3<T> ToRotationMatrix() const;
 			String ToString() const;

include/Nazara/Math/Quaternion.inl

@@ -463,13 +463,27 @@ namespace Nz
 		return w * w + x * x + y * y + z * z;
 	}
 
+	/*!
+	* \brief Returns the "roll angle" of this quaternion
+	* \return Roll rotation
+	*
+	* \remark This function only has sense when quaternion only represents a "roll rotation"
+	*/
+	template<typename T>
+	RadianAngle<T> Quaternion<T>::To2DAngle() const
+	{
+		T siny_cosp = T(2.0) * (w * z + x * y);
+		T cosy_cosp = T(1.0) - T(2.0) * (y * y + z * z);
+
+		return std::atan2(siny_cosp, cosy_cosp);
+	}
+
 	/*!
 	* \brief Converts this quaternion to Euler angles representation
 	* \return EulerAngles which is the representation of this rotation
 	*
 	* \remark Rotation are "left-handed"
 	*/
-
 	template<typename T>
 	EulerAngles<T> Quaternion<T>::ToEulerAngles() const
 	{