Add tiny quaternion stub

Makefile.am

@@ -87,6 +87,8 @@ UTIL_FILES   =		\
     pool.cpp		\
     pool.hpp		\
     preprocessor.hpp	\
+    quaternion.cpp	\
+    quaternion.hpp	\
     raii.hpp		\
     random.cpp		\
     random.hpp		\

quaternion.cpp

@@ -0,0 +1,68 @@
+/*
+ * 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 2011 Danny Robson <danny@nerdcruft.net>
+ */
+
+
+#include "quaternion.hpp"
+
+//-----------------------------------------------------------------------------
+using util::quaternion;
+
+
+//-----------------------------------------------------------------------------
+const quaternion quaternion::IDENTITY = { 1.0, 0.0, 0.0, 0.0 };
+
+
+//-----------------------------------------------------------------------------
+quaternion
+quaternion::rotation (double radians, vector<3> axis) {
+    radians /= 2.0;
+    axis.normalise ();
+
+    return {
+        cos (radians),
+        axis.x * sin (radians),
+        axis.y * sin (radians),
+        axis.z * sin (radians)
+    };
+}
+
+
+quaternion
+quaternion::rotation (vector<3> from, vector<3> to) {
+    auto v = util::cross (from, to);
+
+    return {
+        acos (from.dot (to)),
+        v.x,
+        v.y,
+        v.z
+    };
+}
+
+
+quaternion
+quaternion::operator* (const quaternion &rhs) const {
+    return {
+        w * rhs.w - (x * rhs.x + y * rhs.y + z * rhs.z),
+        w * rhs.x + rhs.w * x + y * rhs.z - z * rhs.y,
+        w * rhs.y + rhs.w * y + z * rhs.x - x * rhs.z,
+        w * rhs.z + rhs.w * z + x * rhs.y - y * rhs.x
+    };
+}
+

quaternion.hpp

@@ -0,0 +1,40 @@
+/*
+ * 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 2011 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef __UTIL_QUATERNION_HPP
+#define __UTIL_QUATERNION_HPP
+
+#include "annotations.hpp"
+#include "vector.hpp"
+
+namespace util {
+    struct quaternion {
+        double w, x, y, z;
+
+        static const quaternion IDENTITY;
+
+        static quaternion rotation (double radians, vector<3> axis) mustuse;
+        static quaternion rotation (vector<3> from, vector<3> to) mustuse;
+
+        quaternion operator* (const quaternion&) const;
+    };
+}
+
+
+#endif