1/// @ref gtx_vector_angle
2
3namespace glm
4{
5	template<typename genType>
6	GLM_FUNC_QUALIFIER genType angle
7	(
8		genType const& x,
9		genType const& y
10	)
11	{
12		GLM_STATIC_ASSERT(std::numeric_limits<genType>::is_iec559, "'angle' only accept floating-point inputs");
13		return acos(clamp(dot(x, y), genType(-1), genType(1)));
14	}
15
16	template<length_t L, typename T, qualifier Q>
17	GLM_FUNC_QUALIFIER T angle(vec<L, T, Q> const& x, vec<L, T, Q> const& y)
18	{
19		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'angle' only accept floating-point inputs");
20		return acos(clamp(dot(x, y), T(-1), T(1)));
21	}
22
23	//! \todo epsilon is hard coded to 0.01
24	template<typename T, qualifier Q>
25	GLM_FUNC_QUALIFIER T orientedAngle(vec<2, T, Q> const& x, vec<2, T, Q> const& y)
26	{
27		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'orientedAngle' only accept floating-point inputs");
28		T const Angle(acos(clamp(dot(x, y), T(-1), T(1))));
29
30		if(all(epsilonEqual(y, glm::rotate(x, Angle), T(0.0001))))
31			return Angle;
32		else
33			return -Angle;
34	}
35
36	template<typename T, qualifier Q>
37	GLM_FUNC_QUALIFIER T orientedAngle(vec<3, T, Q> const& x, vec<3, T, Q> const& y, vec<3, T, Q> const& ref)
38	{
39		GLM_STATIC_ASSERT(std::numeric_limits<T>::is_iec559, "'orientedAngle' only accept floating-point inputs");
40
41		T const Angle(acos(clamp(dot(x, y), T(-1), T(1))));
42		return mix(Angle, -Angle, dot(ref, cross(x, y)) < T(0));
43	}
44}//namespace glm
45