From 56a73275c1f13bfc16e5ca9e32ed988674d0ec5b Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Fri, 20 Apr 2018 15:04:54 +1000
Subject: [PATCH] geom/line: add basic line class

---
 CMakeLists.txt     |  4 +++
 geom/line.cpp      |  0
 geom/line.hpp      | 63 ++++++++++++++++++++++++++++++++++++++++++++++
 test/geom/line.cpp | 28 +++++++++++++++++++++
 4 files changed, 95 insertions(+)
 create mode 100644 geom/line.cpp
 create mode 100644 geom/line.hpp
 create mode 100644 test/geom/line.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8abd6090..e597cd9b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -233,6 +233,8 @@ list (
     geom/frustum.hpp
     geom/iostream.cpp
     geom/iostream.hpp
+    geom/line.hpp
+    geom/line.cpp
     geom/ops.hpp
     geom/plane.cpp
     geom/plane.hpp
@@ -496,6 +498,8 @@ if (TESTS)
         geom/aabb
         geom/ellipse
         geom/frustum
+        geom/line
+        geom/plane
         geom/ray
         geom/sphere
         hash/checksum
diff --git a/geom/line.cpp b/geom/line.cpp
new file mode 100644
index 00000000..e69de29b
diff --git a/geom/line.hpp b/geom/line.hpp
new file mode 100644
index 00000000..267a424e
--- /dev/null
+++ b/geom/line.hpp
@@ -0,0 +1,63 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2018 Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#include "../point.hpp"
+#include "../vector.hpp"
+
+namespace util::geom {
+    // an line of infinite extent that passes though 'base'.
+    //
+    // direction should be normalised
+    template <size_t S, typename T>
+    struct line {
+        line () = default;
+        line (util::point<S,T> a, util::point<S,T> b):
+            line (a, normalised (b - a))
+        { ; }
+
+        line (util::point<S,T> _base, util::vector<S,T> _direction):
+            base (_base),
+            direction (_direction)
+        {
+            CHECK (is_normalised (direction));
+        }
+
+        util::point<S,T> base;
+        util::vector<S,T> direction;
+    };
+
+    using line2f = line<2,float>;
+    using line3f = line<3,float>;
+
+
+    template <size_t S, typename T>
+    T
+    distance2 (line<S,T> l, point<S,T> p)
+    {
+        const auto t = dot (p - l.base, l.direction);
+        return distance2 (p, l.base + l.direction * t);
+    }
+
+
+    template <size_t S, typename T>
+    T
+    distance (line<S,T> l, point<S,T> p)
+    {
+        return std::sqrt (distance2 (l, p));
+    }
+};
diff --git a/test/geom/line.cpp b/test/geom/line.cpp
new file mode 100644
index 00000000..9be94787
--- /dev/null
+++ b/test/geom/line.cpp
@@ -0,0 +1,28 @@
+#include "tap.hpp"
+
+#include "geom/line.hpp"
+
+int
+main (int, char**)
+{
+    util::TAP::logger tap;
+
+    static struct {
+        util::point3f origin;
+        util::vector3f direction;
+        util::point3f q;
+        float distance;
+        const char *message;
+    } TESTS[] = {
+        { { 0, 0, 0 }, { 1, 0, 0}, { 0, 0, 0 }, 0, "origin line, origin point" } ,
+        { { 0, 1, 0 }, { 1, 0, 0}, { 0, 0, 0 }, 1, "+x line, unit distance" },
+    };
+
+    for (auto const& t: TESTS) {
+        util::geom::line3f l { t.origin, t.direction };
+        auto d = distance2 (l, t.q);
+        tap.expect_eq (d, t.distance, "%!", t.message);
+    }
+
+    return tap.status ();
+}
\ No newline at end of file