glm/glm/gtx/vector_angle.inl

///////////////////////////////////////////////////////////////////////////////////////////////////
// OpenGL Mathematics Copyright (c) 2005 - 2011 G-Truc Creation (www.g-truc.net)
///////////////////////////////////////////////////////////////////////////////////////////////////
// Created : 2005-12-30
// Updated : 2008-09-29
// Licence : This source is under MIT License
// File    : glm/gtx/vector_angle.inl
///////////////////////////////////////////////////////////////////////////////////////////////////

namespace glm{

template <typename genType> 
GLM_FUNC_QUALIFIER typename genType::value_type angle
(
	genType const & x, 
	genType const & y
)
{
	return degrees(acos(dot(x, y)));
}

//! \todo epsilon is hard coded to 0.01
template <typename valType> 
GLM_FUNC_QUALIFIER valType orientedAngle
(
	detail::tvec2<valType> const & x, 
	detail::tvec2<valType> const & y
)
{
    valType Angle = glm::degrees(acos(dot(x, y)));
	detail::tvec2<valType> TransformedVector = glm::rotate(x, Angle);
    if(all(equalEpsilon(y, TransformedVector, valType(0.01))))
		return Angle;
    else
        return -Angle;
}

template <typename valType>
GLM_FUNC_QUALIFIER valType orientedAngle
(
	detail::tvec3<valType> const & x,
	detail::tvec3<valType> const & y,
	detail::tvec3<valType> const & ref
)
{
	valType Angle = glm::degrees(glm::acos(glm::dot(x, y)));

	if(glm::dot(ref, glm::cross(x, y)) < valType(0))
		return -Angle;
	else
		return Angle;
}

}//namespace glm