From 6479f63091da35b1ac6f3930532cc8bde466f6c4 Mon Sep 17 00:00:00 2001
From: wwylele <wwylele@gmail.com>
Date: Sun, 11 Dec 2016 23:32:01 +0200
Subject: [PATCH] Common: add Quaternion

---
 src/common/CMakeLists.txt |  1 +
 src/common/quaternion.h   | 44 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 src/common/quaternion.h

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 5aecf6e6e..a7a4a688c 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -46,6 +46,7 @@ set(HEADERS
             microprofileui.h
             platform.h
             profiler_reporting.h
+            quaternion.h
             scm_rev.h
             scope_exit.h
             string_util.h
diff --git a/src/common/quaternion.h b/src/common/quaternion.h
new file mode 100644
index 000000000..84ac82ed3
--- /dev/null
+++ b/src/common/quaternion.h
@@ -0,0 +1,44 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "common/vector_math.h"
+
+namespace Math {
+
+template <typename T>
+class Quaternion {
+public:
+    Math::Vec3<T> xyz;
+    T w;
+
+    Quaternion<decltype(-T{})> Inverse() const {
+        return {-xyz, w};
+    }
+
+    Quaternion<decltype(T{} + T{})> operator+(const Quaternion& other) const {
+        return {xyz + other.xyz, w + other.w};
+    }
+
+    Quaternion<decltype(T{} - T{})> operator-(const Quaternion& other) const {
+        return {xyz - other.xyz, w - other.w};
+    }
+
+    Quaternion<decltype(T{} * T{} - T{} * T{})> operator*(const Quaternion& other) const {
+        return {xyz * other.w + other.xyz * w + Cross(xyz, other.xyz),
+                w * other.w - Dot(xyz, other.xyz)};
+    }
+};
+
+template <typename T>
+auto QuaternionRotate(const Quaternion<T>& q, const Math::Vec3<T>& v) {
+    return v + 2 * Cross(q.xyz, Cross(q.xyz, v) + v * q.w);
+}
+
+inline Quaternion<float> MakeQuaternion(const Math::Vec3<float>& axis, float angle) {
+    return {axis * std::sin(angle / 2), std::cos(angle / 2)};
+}
+
+} // namspace Math