return faceforward, reflect and refract functions

.github/workflows/windows.yml

@@ -14,7 +14,7 @@ jobs:
         - { os: "windows-2016", vs: "Visual Studio 2017", arch: "x64" }
         - { os: "windows-2019", vs: "Visual Studio 2019", arch: "x86" }
         - { os: "windows-2019", vs: "Visual Studio 2019", arch: "x64" }
-    name: "${{matrix.config.vs}}"
+    name: "${{matrix.config.vs}} ${{matrix.config.arch}}"
     steps:
     - uses: actions/checkout@v2
     - name: Build && Test

README.md

@@ -1325,6 +1325,15 @@ constexpr T distance2(T x, T y) noexcept;
 
 template < floating_point T >
 T normalize(T x) noexcept;
+
+template < floating_point T >
+constexpr T faceforward(T n, T i, T nref) noexcept;
+
+template < floating_point T >
+constexpr T reflect(T i, T n) noexcept;
+
+template < floating_point T >
+T refract(T i, T n, T eta) noexcept;
 ```
 
 #### Vector
@@ -1359,6 +1368,15 @@ constexpr vec<T, 3> cross(const vec<T, 3>& xs, const vec<T, 3>& ys);
 
 template < typename T, size_t Size >
 vec<T, Size> normalize(const vec<T, Size>& xs);
+
+template < typename T, size_t Size >
+constexpr vec<T, Size> faceforward(const vec<T, Size>& n, const vec<T, Size>& i, const vec<T, Size>& nref);
+
+template < typename T, size_t Size >
+constexpr vec<T, Size> reflect(const vec<T, Size>& i, const vec<T, Size>& n);
+
+template < typename T, size_t Size >
+vec<T, Size> refract(const vec<T, Size>& i, const vec<T, Size>& n, T eta);
 ```
 
 #### Quaternion

headers/vmath.hpp/vmath_fun.hpp

@@ -358,6 +358,26 @@ namespace vmath_hpp
     normalize(T x) noexcept {
         return x * rlength(x);
     }
+
+    template < typename T >
+    [[nodiscard]] std::enable_if_t<std::is_floating_point_v<T>, T>
+    constexpr faceforward(T n, T i, T nref) noexcept {
+        return dot(nref, i) < T{0} ? n : -n;
+    }
+
+    template < typename T >
+    [[nodiscard]] std::enable_if_t<std::is_floating_point_v<T>, T>
+    constexpr reflect(T i, T n) noexcept {
+        return i - T{2} * dot(n, i) * n;
+    }
+
+    template < typename T >
+    [[nodiscard]] std::enable_if_t<std::is_floating_point_v<T>, T>
+    refract(T i, T n, T eta) noexcept {
+        const T d = dot(n, i);
+        const T k = T{1} - sqr(eta) * (T{1} - sqr(d));
+        return k < T{0} ? T{0} : (eta * i - (eta * d + sqrt(k)) * n);
+    }
 }
 
 //

headers/vmath.hpp/vmath_vec_fun.hpp

@@ -834,6 +834,23 @@ namespace vmath_hpp
     [[nodiscard]] vec<T, Size> normalize(const vec<T, Size>& xs) {
         return xs * rlength(xs);
     }
+
+    template < typename T, std::size_t Size >
+    [[nodiscard]] constexpr vec<T, Size> faceforward(const vec<T, Size>& n, const vec<T, Size>& i, const vec<T, Size>& nref) {
+        return dot(nref, i) < T{0} ? n : -n;
+    }
+
+    template < typename T, std::size_t Size >
+    [[nodiscard]] constexpr vec<T, Size> reflect(const vec<T, Size>& i, const vec<T, Size>& n) {
+        return i - T{2} * dot(n, i) * n;
+    }
+
+    template < typename T, std::size_t Size >
+    [[nodiscard]] vec<T, Size> refract(const vec<T, Size>& i, const vec<T, Size>& n, T eta) {
+        const T d = dot(n, i);
+        const T k = T{1} - sqr(eta) * (T{1} - sqr(d));
+        return k < T{0} ? vec<T, Size>{T{0}} : (eta * i - (eta * d + sqrt(k)) * n);
+    }
 }
 
 //

untests/vmath_fix_tests.cpp

@@ -267,6 +267,9 @@ namespace vmath_hpp
     template fix<float> cross(const fix2f&, const fix2f&);
     template fix3f cross(const fix3f&, const fix3f&);
     template fix2f normalize(const fix2f&);
+    template fix3f faceforward(const fix3f&, const fix3f&, const fix3f&);
+    template fix3f reflect(const fix3f&, const fix3f&);
+    template fix3f refract(const fix3f&, const fix3f&, fix<float>);
 }
 
 namespace vmath_hpp

untests/vmath_fun_tests.cpp

@@ -130,6 +130,10 @@ TEST_CASE("vmath/fun") {
 
         STATIC_CHECK(dot(2.f, 5.f) == uapprox(10.f));
         CHECK(normalize(0.5f) == uapprox(1.f));
+
+        STATIC_CHECK(faceforward(1.f, 2.f, 3.f) == uapprox(-1.f));
+        STATIC_CHECK(reflect(1.f, 2.f) == uapprox(-7.f));
+        CHECK(refract(1.f, 2.f, 1.f) == uapprox(-7.f));
     }
 
     SUBCASE("Relational Functions") {

untests/vmath_vec_fun_tests.cpp

@@ -276,6 +276,10 @@ TEST_CASE("vmath/vec_fun") {
         STATIC_CHECK(cross(int2(1,0),int2(0,1)) == 1);
         STATIC_CHECK(cross(int3(1,0,0),int3(0,1,0)) == int3(0,0,1));
         CHECK(normalize(float2(0.5f,0.f)).x == uapprox(1.f));
+
+        STATIC_CHECK(faceforward(float2(1.f), float2(2.f), float2(3.f)).x == uapprox(-1.f));
+        STATIC_CHECK(reflect(float2(1.f), float2(2.f)).x == uapprox(-15.f));
+        CHECK(refract(float2(1.f), float2(2.f), 1.f).x == uapprox(-15.f));
     }
 
     SUBCASE("Relational Functions") {