From 75358451eacf530f25e4320c5a8a23a20c176cc8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Mon, 27 Dec 2010 18:38:16 +0100
Subject: [PATCH] Function for angle between vectors.

---
 src/Math/Test/VectorTest.cpp | 8 ++++++++
 src/Math/Test/VectorTest.h   | 1 +
 src/Math/Vector.h            | 5 +++++
 3 files changed, 14 insertions(+)

diff --git a/src/Math/Test/VectorTest.cpp b/src/Math/Test/VectorTest.cpp
index c4f0ebe88..a60af9923 100644
--- a/src/Math/Test/VectorTest.cpp
+++ b/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);
+}
+
 }}}
diff --git a/src/Math/Test/VectorTest.h b/src/Math/Test/VectorTest.h
index e2d42a422..83a2917d3 100644
--- a/src/Math/Test/VectorTest.h
+++ b/src/Math/Test/VectorTest.h
@@ -32,6 +32,7 @@ class VectorTest: public QObject {
         void addSubstract();
         void length();
         void normalized();
+        void angle();
 };
 
 }}}
diff --git a/src/Math/Vector.h b/src/Math/Vector.h
index ffeac7f40..e7ce856e1 100644
--- a/src/Math/Vector.h
+++ b/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));