text: ///////////////////////////////////////////////////////////////////////////////////
  /// OpenGL Mathematics (glm.g-truc.net)
  ///
  /// Copyright (c) 2005 - 2014 G-Truc Creation (www.g-truc.net)
  /// Permission is hereby granted, free of charge, to any person obtaining a copy
  /// of this software and associated documentation files (the "Software"), to deal
  /// in the Software without restriction, including without limitation the rights
  /// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  /// copies of the Software, and to permit persons to whom the Software is
  /// furnished to do so, subject to the following conditions:
  /// 
  /// The above copyright notice and this permission notice shall be included in
  /// all copies or substantial portions of the Software.
  /// 
  /// Restrictions:
  ///		By making use of the Software for military purposes, you choose to make
  ///		a Bunny unhappy.
  /// 
  /// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  /// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  /// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  /// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  /// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  /// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  /// THE SOFTWARE.
  ///
  /// @ref core
  /// @file glm/detail/func_geometric.inl
  /// @date 2008-08-03 / 2011-06-15
  /// @author Christophe Riccio
  ///////////////////////////////////////////////////////////////////////////////////
  
  #include "func_exponential.hpp"
  #include "func_common.hpp"
  #include "type_vec2.hpp"
  #include "type_vec4.hpp"
  #include "type_float.hpp"
  
  namespace glm{
  namespace detail
  {
  	template <template <class, precision> class vecType, typename T, precision P>
  	struct compute_dot{};
  
  	template <typename T, precision P>
  	struct compute_dot<tvec1, T, P>
  	{
  		GLM_FUNC_QUALIFIER static T call(tvec1<T, P> const & a, tvec1<T, P> const & b)
  		{
  			return a.x * b.x;
  		}
  	};
  
  	template <typename T, precision P>
  	struct compute_dot<tvec2, T, P>
  	{
  		GLM_FUNC_QUALIFIER static T call(tvec2<T, P> const & x, tvec2<T, P> const & y)
  		{
  			tvec2<T, P> tmp(x * y);
  			return tmp.x + tmp.y;
  		}
  	};
  
  	template <typename T, precision P>
  	struct compute_dot<tvec3, T, P>
  	{
  		GLM_FUNC_QUALIFIER static T call(tvec3<T, P> const & x, tvec3<T, P> const & y)
  		{
  			tvec3<T, P> tmp(x * y);
  			return tmp.x + tmp.y + tmp.z;
  		}
  	};
  
  	template <typename T, precision P>
  	struct compute_dot<tvec4, T, P>
  	{
  		GLM_FUNC_QUALIFIER static T call(tvec4<T, P> const & x, tvec4<T, P> const & y)
  		{
  			tvec4<T, P> tmp(x * y);
  			return (tmp.x + tmp.y) + (tmp.z + tmp.w);
  		}
  	};
  }//namespace detail
  
  	// length
  	template <typename genType>
  	GLM_FUNC_QUALIFIER genType length(genType x)
  	{
  		GLM_STATIC_ASSERT(std::numeric_limits<genType>::is_iec559, "'length' only accept floating-point inputs");
  
  		return abs(x);
  	}
  
  	template <typename T, precision P, template <typename, precision> class vecType>
  	GLM_FUNC_QUALIFIER T length(vecType<T, P> const & v)
  	{
  		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'length' only accept floating-point inputs");
  
  		return sqrt(dot(v, v));
  	}
  
  	// distance
  	template <typename genType>
  	GLM_FUNC_QUALIFIER genType distance(genType const & p0, genType const & p1)
  	{
  		GLM_STATIC_ASSERT(std::numeric_limits<genType>::is_iec559, "'distance' only accept floating-point inputs");
  
  		return length(p1 - p0);
  	}
  
  	template <typename T, precision P, template <typename, precision> class vecType>
  	GLM_FUNC_QUALIFIER T distance(vecType<T, P> const & p0, vecType<T, P> const & p1)
  	{
  		return length(p1 - p0);
  	}
  
  	// dot
  	template <typename T>
  	GLM_FUNC_QUALIFIER T dot(T x, T y)
  	{
  		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'dot' only accept floating-point inputs");
  		return x * y;
  	}
  
  	template <typename T, precision P, template <typename, precision> class vecType>
  	GLM_FUNC_QUALIFIER T dot(vecType<T, P> const & x, vecType<T, P> const & y)
  	{
  		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'dot' only accept floating-point inputs");
  		return detail::compute_dot<vecType, T, P>::call(x, y);
  	}
  
  	// cross
  	template <typename T, precision P>
  	GLM_FUNC_QUALIFIER tvec3<T, P> cross(tvec3<T, P> const & x, tvec3<T, P> const & y)
  	{
  		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'cross' only accept floating-point inputs");
  
  		return tvec3<T, P>(
  			x.y * y.z - y.y * x.z,
  			x.z * y.x - y.z * x.x,
  			x.x * y.y - y.x * x.y);
  	}
  
  	// normalize
  	template <typename genType>
  	GLM_FUNC_QUALIFIER genType normalize(genType const & x)
  	{
  		GLM_STATIC_ASSERT(std::numeric_limits<genType>::is_iec559, "'normalize' only accept floating-point inputs");
  
  		return x < genType(0) ? genType(-1) : genType(1);
  	}
  
  	template <typename T, precision P, template <typename, precision> class vecType>
  	GLM_FUNC_QUALIFIER vecType<T, P> normalize(vecType<T, P> const & x)
  	{
  		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'normalize' only accept floating-point inputs");
  
  		return x * inversesqrt(dot(x, x));
  	}
  
  	// faceforward
  	template <typename genType>
  	GLM_FUNC_QUALIFIER genType faceforward(genType const & N, genType const & I, genType const & Nref)
  	{
  		return dot(Nref, I) < static_cast<genType>(0) ? N : -N;
  	}
  
  	// reflect
  	template <typename genType>
  	GLM_FUNC_QUALIFIER genType reflect(genType const & I, genType const & N)
  	{
  		return I - N * dot(N, I) * static_cast<genType>(2);
  	}
  
  	// refract
  	template <typename genType>
  	GLM_FUNC_QUALIFIER genType refract(genType const & I, genType const & N, genType const & eta)
  	{
  		GLM_STATIC_ASSERT(std::numeric_limits<genType>::is_iec559, "'refract' only accept floating-point inputs");
  
  		genType const dotValue(dot(N, I));
  		genType const k(static_cast<genType>(1) - eta * eta * (static_cast<genType>(1) - dotValue * dotValue));
  		return (eta * I - (eta * dotValue + sqrt(k)) * N) * static_cast<genType>(k >= static_cast<genType>(0));
  	}
  
  	template <typename T, precision P, template <typename, precision> class vecType>
  	GLM_FUNC_QUALIFIER vecType<T, P> refract(vecType<T, P> const & I, vecType<T, P> const & N, T eta)
  	{
  		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'refract' only accept floating-point inputs");
  
  		T const dotValue(dot(N, I));
  		T const k(static_cast<T>(1) - eta * eta * (static_cast<T>(1) - dotValue * dotValue));
  		return (eta * I - (eta * dotValue + std::sqrt(k)) * N) * static_cast<T>(k >= static_cast<T>(0));
  	}
  }//namespace glm
  