Function for angle between vectors.

src/Math/Test/VectorTest.cpp

@@ -26,6 +26,7 @@ using namespace std;
 namespace Magnum { namespace Math { namespace Test {
 
 typedef Vector<float, 4> Vector4;
+typedef Vector<float, 3> Vector3;
 
 void VectorTest::construct() {
     float zero[] = { 0.0f, 0.0f, 0.0f, 0.0f };
@@ -117,4 +118,11 @@ void VectorTest::normalized() {
     QVERIFY(Vector4(vec).normalized() == Vector4(normalized));
 }
 
+void VectorTest::angle() {
+    float a[] = { 2.0f, 3.0f, 4.0f };
+    float b[] = { 1.0f, -2.0f, 3.0f };
+
+    QCOMPARE(Vector3::angle(a, b), 1.16251f);
+}
+
 }}}

src/Math/Test/VectorTest.h

@@ -32,6 +32,7 @@ class VectorTest: public QObject {
         void addSubstract();
         void length();
         void normalized();
+        void angle();
 };
 
 }}}

src/Math/Vector.h

@@ -29,6 +29,11 @@ namespace Magnum { namespace Math {
 /** @brief Vector */
 template<class T, size_t size> class Vector {
     public:
+        /** @brief Angle between vectors */
+        inline static T angle(const Vector<T, size>& a, const Vector<T, size>& b) {
+            return acos((a*b)/(a.length()*b.length()));
+        }
+
         /** @brief Default constructor */
         inline Vector() {
             memset(_data, 0, size*sizeof(T));