From 5f19343bee432bc81ccf49bffaebc697389fd626 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Mon, 7 Jan 2013 01:22:51 +0100
Subject: [PATCH] Math: linear interpolation of two Vectors.

---
 src/Math/Test/VectorTest.cpp |  9 +++++++++
 src/Math/Vector.h            | 17 +++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/src/Math/Test/VectorTest.cpp b/src/Math/Test/VectorTest.cpp
index d8d9f303f..b1f93a472 100644
--- a/src/Math/Test/VectorTest.cpp
+++ b/src/Math/Test/VectorTest.cpp
@@ -41,6 +41,7 @@ class VectorTest: public Corrade::TestSuite::Tester {
         void min();
         void max();
         void angle();
+        void lerp();
 
         void debug();
         void configuration();
@@ -63,6 +64,7 @@ VectorTest::VectorTest() {
              &VectorTest::min,
              &VectorTest::max,
              &VectorTest::angle,
+             &VectorTest::lerp,
              &VectorTest::debug,
              &VectorTest::configuration);
 }
@@ -153,6 +155,13 @@ void VectorTest::angle() {
                     rad(1.162514f));
 }
 
+void VectorTest::lerp() {
+    Vector3 a(-1.0f, 2.0f, 3.0f);
+    Vector3 b(3.0f, -2.0f, 11.0f);
+
+    CORRADE_COMPARE(Vector3::lerp(a, b, 0.25f), Vector3(0.0f, 1.0f, 5.0f));
+}
+
 void VectorTest::debug() {
     std::ostringstream o;
     Debug(&o) << Vector4(0.5f, 15.0f, 1.0f, 1.0f);
diff --git a/src/Math/Vector.h b/src/Math/Vector.h
index 5cb7d25c2..d21fde555 100644
--- a/src/Math/Vector.h
+++ b/src/Math/Vector.h
@@ -67,6 +67,20 @@ template<std::size_t size, class T> class Vector: public RectangularMatrix<1, si
             return std::acos(dot(normalizedA, normalizedB));
         }
 
+        /**
+         * @brief Linear interpolation of two vectors
+         * @param a     First vector
+         * @param b     Second vector
+         * @param t     Interpolation phase (from range @f$ [0; 1] @f$)
+         *
+         * The interpolation is done as in following: @f[
+         *      v_{LERP} = (1 - t) \boldsymbol v_A + t \boldsymbol v_B
+         * @f]
+         */
+        inline static Vector<size, T> lerp(const Vector<size, T>& a, const Vector<size, T>& b, T t) {
+            return (T(1) - t)*a + t*b;
+        }
+
         /** @brief Default constructor */
         inline constexpr /*implicit*/ Vector() {}
 
@@ -345,6 +359,9 @@ extern template Corrade::Utility::Debug MAGNUM_EXPORT operator<<(Corrade::Utilit
     }                                                                       \
     template<class U> inline constexpr static Type<T> from(const Math::Vector<size, U>& other) { \
         return Math::Vector<size, T>::from(other);                          \
+    }                                                                       \
+    inline static const Type<T> lerp(const Math::Vector<size, T>& a, const Math::Vector<size, T>& b, T t) { \
+        return Math::Vector<size, T>::lerp(a, b, t);                        \
     }                                                                       \
                                                                             \
     inline Type<T>& operator=(const Type<T>& other) {                       \