1 files changed, 89 insertions, 0 deletions

diff --git a/src/core/frontend/motion_emu.cpp b/src/core/frontend/motion_emu.cpp
new file mode 100644
index 000000000..9a5b3185d
--- /dev/null
+++ b/src/core/frontend/motion_emu.cpp
@@ -0,0 +1,89 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "common/math_util.h"
+#include "common/quaternion.h"
+#include "core/frontend/emu_window.h"
+#include "core/frontend/motion_emu.h"
+
+namespace Motion {
+
+static constexpr int update_millisecond = 100;
+static constexpr auto update_duration =
+    std::chrono::duration_cast<std::chrono::steady_clock::duration>(
+        std::chrono::milliseconds(update_millisecond));
+
+MotionEmu::MotionEmu(EmuWindow& emu_window)
+    : motion_emu_thread(&MotionEmu::MotionEmuThread, this, std::ref(emu_window)) {}
+
+MotionEmu::~MotionEmu() {
+    if (motion_emu_thread.joinable()) {
+        shutdown_event.Set();
+        motion_emu_thread.join();
+    }
+}
+
+void MotionEmu::MotionEmuThread(EmuWindow& emu_window) {
+    auto update_time = std::chrono::steady_clock::now();
+    Math::Quaternion<float> q = MakeQuaternion(Math::Vec3<float>(), 0);
+    Math::Quaternion<float> old_q;
+
+    while (!shutdown_event.WaitUntil(update_time)) {
+        update_time += update_duration;
+        old_q = q;
+
+        {
+            std::lock_guard<std::mutex> guard(tilt_mutex);
+
+            // Find the quaternion describing current 3DS tilting
+            q = MakeQuaternion(Math::MakeVec(-tilt_direction.y, 0.0f, tilt_direction.x),
+                               tilt_angle);
+        }
+
+        auto inv_q = q.Inverse();
+
+        // Set the gravity vector in world space
+        auto gravity = Math::MakeVec(0.0f, -1.0f, 0.0f);
+
+        // Find the angular rate vector in world space
+        auto angular_rate = ((q - old_q) * inv_q).xyz * 2;
+        angular_rate *= 1000 / update_millisecond / MathUtil::PI * 180;
+
+        // Transform the two vectors from world space to 3DS space
+        gravity = QuaternionRotate(inv_q, gravity);
+        angular_rate = QuaternionRotate(inv_q, angular_rate);
+
+        // Update the sensor state
+        emu_window.AccelerometerChanged(gravity.x, gravity.y, gravity.z);
+        emu_window.GyroscopeChanged(angular_rate.x, angular_rate.y, angular_rate.z);
+    }
+}
+
+void MotionEmu::BeginTilt(int x, int y) {
+    mouse_origin = Math::MakeVec(x, y);
+    is_tilting = true;
+}
+
+void MotionEmu::Tilt(int x, int y) {
+    constexpr float SENSITIVITY = 0.01f;
+    auto mouse_move = Math::MakeVec(x, y) - mouse_origin;
+    if (is_tilting) {
+        std::lock_guard<std::mutex> guard(tilt_mutex);
+        if (mouse_move.x == 0 && mouse_move.y == 0) {
+            tilt_angle = 0;
+        } else {
+            tilt_direction = mouse_move.Cast<float>();
+            tilt_angle = MathUtil::Clamp(tilt_direction.Normalize() * SENSITIVITY, 0.0f,
+                                         MathUtil::PI * 0.5f);
+        }
+    }
+}
+
+void MotionEmu::EndTilt() {
+    std::lock_guard<std::mutex> guard(tilt_mutex);
+    tilt_angle = 0;
+    is_tilting = false;
+}
+
+} // namespace Motion