line: add trivial line type

Makefile.am

@@ -77,6 +77,8 @@ UTIL_FILES   =		\
     json/tree.hpp	\
     lerp.cpp		\
     lerp.hpp		\
+    line.cpp		\
+    line.hpp		\
     log.cpp		\
     log.hpp		\
     log.ipp		\
@@ -239,6 +241,7 @@ TEST_BIN = 			\
     test/hton			\
     test/ip 			\
     test/json_types		\
+    test/line			\
     test/maths			\
     test/maths_matrix 		\
     test/matrix			\

line.cpp

@@ -0,0 +1,60 @@
+/*
+ * This file is part of libgim.
+ *
+ * libgim is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * libgim is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#include "line.hpp"
+
+#include "debug.hpp"
+
+
+//-----------------------------------------------------------------------------
+template <size_t S, typename T>
+util::line<S,T>::line (util::point<S,T> _p,
+                       util::vector<S,T> _d):
+    p (_p),
+    d (_d)
+{
+    CHECK_EQ (d.magnitude2 (), 1);
+}
+
+
+///----------------------------------------------------------------------------
+/// returns the distance alone the line in a line-plane intersection
+///
+/// returns inf if parallel
+/// returns 0   if colinear
+template <size_t S, typename T>
+T
+util::line<S,T>::intersect (plane<S,T> rhs) const
+{
+    return dot (rhs.p - p, rhs.n) / dot (d, rhs.n);
+}
+
+
+//-----------------------------------------------------------------------------
+template <size_t S, typename T>
+util::point<S,T>
+util::line<S,T>::at (T t) const
+{
+    return p + d * t;
+}
+
+
+//-----------------------------------------------------------------------------
+template struct util::line<2,float>;
+template struct util::line<3,float>;

line.hpp

@@ -0,0 +1,46 @@
+/*
+ * This file is part of libgim.
+ *
+ * libgim is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * libgim is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with libgim.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef __UTIL_LINE_HPP
+#define __UTIL_LINE_HPP
+
+#include "point.hpp"
+#include "vector.hpp"
+#include "plane.hpp"
+
+namespace util {
+    template <size_t S, typename T>
+    struct line {
+        line (util::point<S,T> place,
+              util::vector<S,T> direction);
+
+        T intersect (plane<S,T>) const;
+
+        util::point<S,T> at (T) const;
+
+        util::point<S,T> p;
+        util::vector<S,T> d;
+    };
+
+
+    typedef line<2,float> line2f;
+    typedef line<3,float> line3f;
+}
+
+#endif

test/line.cpp

@@ -0,0 +1,13 @@
+#include "line.hpp"
+#include "plane.hpp"
+#include "debug.hpp"
+
+int
+main (void)
+{
+    // trivial case: origin line facing z, plane at unit z facing -z.
+    util::line3f  l ({0,0,0}, {0,0, 1});
+    util::plane3f p ({0,0,1}, {0,0,-1});
+
+    CHECK_EQ (l.intersect (p), 1);
+}