From 6ac02a9920443c517b7e7212381a5b3bae1d90d2 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Thu, 19 Feb 2015 13:19:27 +1100
Subject: [PATCH] point: add homogenous redim

---
 point.hpp      |  2 ++
 point.ipp      | 27 +++++++++++++++++++++++++++
 test/point.cpp | 10 ++++++++++
 3 files changed, 39 insertions(+)

diff --git a/point.hpp b/point.hpp
index 34d73680..b244799a 100644
--- a/point.hpp
+++ b/point.hpp
@@ -61,6 +61,8 @@ namespace util {
         template <size_t D> point<D,T> redim (const util::point<D,T> &fill) const;
         template <size_t D> point<D,T> redim (T fill) const;
 
+        template <size_t D> point<D,T> homog (void) const;
+
         static const point<S,T> ORIGIN;
 
         template<typename U> point<S,U> cast (void) const;
diff --git a/point.ipp b/point.ipp
index bef9db60..5c2abf0c 100644
--- a/point.ipp
+++ b/point.ipp
@@ -111,6 +111,33 @@ namespace util {
     }
 
 
+    ///------------------------------------------------------------------------
+    /// expand point to use homogenous coordinates of a higher dimension.
+    /// ie, fill with (0,..,0,1)
+    template <size_t S, typename T>
+    template <size_t D>
+    point<D,T>
+    point<S,T>::homog (void) const
+    {
+        static_assert (D > S, "homog will not overwrite data");
+
+        point<D,T> out;
+
+        // Copy the existing data
+        auto c = std::copy (this->begin (),
+                            this->end (),
+                            out.begin ());
+
+        // Fill until the second last element with zeros
+        auto f = std::fill_n (c, D - S - 1, T{0});
+
+        // Last element should be one
+        *f = T{1};
+
+        return out;
+    }
+
+
     //-------------------------------------------------------------------------
     template <size_t S, typename T>
     template <typename U>
diff --git a/test/point.cpp b/test/point.cpp
index 29ea275a..b46ac108 100644
--- a/test/point.cpp
+++ b/test/point.cpp
@@ -37,4 +37,14 @@ main (int, char**) {
         CHECK_EQ (q.data[2], FILL.data[2]);
         CHECK_EQ (q.data[3], FILL.data[3]);
     }
+
+    {
+        const point2f p (3, 4);
+        const point4f q = p.homog<4> ();
+
+        CHECK_EQ (q.x, 3);
+        CHECK_EQ (q.y, 4);
+        CHECK_EQ (q.z, 0);
+        CHECK_EQ (q.w, 1);
+    }
 }