3 files changed, 246 insertions, 0 deletions

diff --git a/src/input_common/CMakeLists.txt b/src/input_common/CMakeLists.txt
index 32433df25..09361e37e 100644
--- a/src/input_common/CMakeLists.txt
+++ b/src/input_common/CMakeLists.txt
@@ -7,6 +7,8 @@ add_library(input_common STATIC
     main.h
     motion_emu.cpp
     motion_emu.h
+    motion_input.cpp
+    motion_input.h
     settings.cpp
     settings.h
     touch_from_button.cpp
diff --git a/src/input_common/motion_input.cpp b/src/input_common/motion_input.cpp
new file mode 100644
index 000000000..88fddb1b9
--- /dev/null
+++ b/src/input_common/motion_input.cpp
@@ -0,0 +1,176 @@
+#include "input_common/motion_input.h"
+
+namespace InputCommon {
+
+MotionInput::MotionInput(f32 new_kp, f32 new_ki, f32 new_kd)
+    : kp(new_kp), ki(new_ki), kd(new_kd), quat{{0, 0, -1}, 0} {}
+
+void MotionInput::SetAcceleration(const Common::Vec3f& acceleration) {
+    accel = acceleration;
+}
+
+void MotionInput::SetGyroscope(const Common::Vec3f& gyroscope) {
+    gyro = gyroscope - gyro_drift;
+    if (gyro.Length2() < gyro_threshold) {
+        gyro = {};
+    }
+}
+
+void MotionInput::SetQuaternion(const Common::Quaternion<f32>& quaternion) {
+    quat = quaternion;
+}
+
+void MotionInput::SetGyroDrift(const Common::Vec3f& drift) {
+    gyro_drift = drift;
+}
+
+void MotionInput::SetGyroThreshold(f32 threshold) {
+    gyro_threshold = threshold;
+}
+
+void MotionInput::EnableReset(bool reset) {
+    reset_enabled = reset;
+}
+
+void MotionInput::ResetRotations() {
+    rotations = {};
+}
+
+bool MotionInput::IsMoving(f32 sensitivity) const {
+    return gyro.Length() >= sensitivity || accel.Length() <= 0.9f || accel.Length() >= 1.1f;
+}
+
+bool MotionInput::IsCalibrated(f32 sensitivity) const {
+    return real_error.Length() < sensitivity;
+}
+
+void MotionInput::UpdateRotation(u64 elapsed_time) {
+    const f32 sample_period = elapsed_time / 1000000.0f;
+    if (sample_period > 0.1f) {
+        return;
+    }
+    rotations += gyro * sample_period;
+}
+
+void MotionInput::UpdateOrientation(u64 elapsed_time) {
+    if (!IsCalibrated(0.1f)) {
+        ResetOrientation();
+    }
+    // Short name local variable for readability
+    f32 q1 = quat.w;
+    f32 q2 = quat.xyz[0];
+    f32 q3 = quat.xyz[1];
+    f32 q4 = quat.xyz[2];
+    const f32 sample_period = elapsed_time / 1000000.0f;
+
+    // ignore invalid elapsed time
+    if (sample_period > 0.1f) {
+        return;
+    }
+
+    const auto normal_accel = accel.Normalized();
+    auto rad_gyro = gyro * 3.1415926535f * 2;
+    const f32 swap = rad_gyro.x;
+    rad_gyro.x = rad_gyro.y;
+    rad_gyro.y = -swap;
+    rad_gyro.z = -rad_gyro.z;
+
+    // Ignore drift correction if acceleration is not reliable
+    if (accel.Length() >= 0.75f && accel.Length() <= 1.25f) {
+        const f32 ax = -normal_accel.x;
+        const f32 ay = normal_accel.y;
+        const f32 az = -normal_accel.z;
+
+        // Estimated direction of gravity
+        const f32 vx = 2.0f * (q2 * q4 - q1 * q3);
+        const f32 vy = 2.0f * (q1 * q2 + q3 * q4);
+        const f32 vz = q1 * q1 - q2 * q2 - q3 * q3 + q4 * q4;
+
+        // Error is cross product between estimated direction and measured direction of gravity
+        const Common::Vec3f new_real_error = {az * vx - ax * vz, ay * vz - az * vy,
+                                              ax * vy - ay * vx};
+
+        derivative_error = new_real_error - real_error;
+        real_error = new_real_error;
+
+        // Prevent integral windup
+        if (ki != 0.0f && !IsCalibrated(0.05f)) {
+            integral_error += real_error;
+        } else {
+            integral_error = {};
+        }
+
+        // Apply feedback terms
+        rad_gyro += kp * real_error;
+        rad_gyro += ki * integral_error;
+        rad_gyro += kd * derivative_error;
+    }
+
+    const f32 gx = rad_gyro.y;
+    const f32 gy = rad_gyro.x;
+    const f32 gz = rad_gyro.z;
+
+    // Integrate rate of change of quaternion
+    const f32 pa = q2;
+    const f32 pb = q3;
+    const f32 pc = q4;
+    q1 = q1 + (-q2 * gx - q3 * gy - q4 * gz) * (0.5f * sample_period);
+    q2 = pa + (q1 * gx + pb * gz - pc * gy) * (0.5f * sample_period);
+    q3 = pb + (q1 * gy - pa * gz + pc * gx) * (0.5f * sample_period);
+    q4 = pc + (q1 * gz + pa * gy - pb * gx) * (0.5f * sample_period);
+
+    quat.w = q1;
+    quat.xyz[0] = q2;
+    quat.xyz[1] = q3;
+    quat.xyz[2] = q4;
+    quat = quat.Normalized();
+}
+
+std::array<Common::Vec3f, 3> MotionInput::GetOrientation() const {
+    const Common::Quaternion<float> quad{
+        .xyz = {-quat.xyz[1], -quat.xyz[0], -quat.w},
+        .w = -quat.xyz[2],
+    };
+    const std::array<float, 16> matrix4x4 = quad.ToMatrix();
+
+    return {Common::Vec3f(matrix4x4[0], matrix4x4[1], -matrix4x4[2]),
+            Common::Vec3f(matrix4x4[4], matrix4x4[5], -matrix4x4[6]),
+            Common::Vec3f(-matrix4x4[8], -matrix4x4[9], matrix4x4[10])};
+}
+
+Common::Vec3f MotionInput::GetAcceleration() const {
+    return accel;
+}
+
+Common::Vec3f MotionInput::GetGyroscope() const {
+    return gyro;
+}
+
+Common::Quaternion<f32> MotionInput::GetQuaternion() const {
+    return quat;
+}
+
+Common::Vec3f MotionInput::GetRotations() const {
+    return rotations;
+}
+
+void MotionInput::ResetOrientation() {
+    if (!reset_enabled) {
+        return;
+    }
+    if (!IsMoving(0.5f) && accel.z <= -0.9f) {
+        ++reset_counter;
+        if (reset_counter > 900) {
+            // TODO: calculate quaternion from gravity vector
+            quat.w = 0;
+            quat.xyz[0] = 0;
+            quat.xyz[1] = 0;
+            quat.xyz[2] = -1;
+            integral_error = {};
+            reset_counter = 0;
+        }
+    } else {
+        reset_counter = 0;
+    }
+}
+} // namespace InputCommon
diff --git a/src/input_common/motion_input.h b/src/input_common/motion_input.h
new file mode 100644
index 000000000..445798a54
--- /dev/null
+++ b/src/input_common/motion_input.h
@@ -0,0 +1,68 @@
+// Copyright 2014 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "common/common_types.h"
+#include "common/quaternion.h"
+#include "common/vector_math.h"
+
+namespace InputCommon {
+
+class MotionInput {
+public:
+    MotionInput(f32 new_kp, f32 new_ki, f32 new_kd);
+
+    MotionInput(const MotionInput&) = default;
+    MotionInput& operator=(const MotionInput&) = default;
+
+    MotionInput(MotionInput&&) = default;
+    MotionInput& operator=(MotionInput&&) = default;
+
+    void SetAcceleration(const Common::Vec3f& acceleration);
+    void SetGyroscope(const Common::Vec3f& acceleration);
+    void SetQuaternion(const Common::Quaternion<f32>& quaternion);
+    void SetGyroDrift(const Common::Vec3f& drift);
+    void SetGyroThreshold(f32 threshold);
+
+    void EnableReset(bool reset);
+    void ResetRotations();
+
+    void UpdateRotation(u64 elapsed_time);
+    void UpdateOrientation(u64 elapsed_time);
+
+    std::array<Common::Vec3f, 3> GetOrientation() const;
+    Common::Vec3f GetAcceleration() const;
+    Common::Vec3f GetGyroscope() const;
+    Common::Vec3f GetRotations() const;
+    Common::Quaternion<f32> GetQuaternion() const;
+
+    bool IsMoving(f32 sensitivity) const;
+    bool IsCalibrated(f32 sensitivity) const;
+
+private:
+    void ResetOrientation();
+
+    // PID constants
+    const f32 kp;
+    const f32 ki;
+    const f32 kd;
+
+    // PID errors
+    Common::Vec3f real_error;
+    Common::Vec3f integral_error;
+    Common::Vec3f derivative_error;
+
+    Common::Quaternion<f32> quat;
+    Common::Vec3f rotations;
+    Common::Vec3f accel;
+    Common::Vec3f gyro;
+    Common::Vec3f gyro_drift;
+
+    f32 gyro_threshold = 0.0f;
+    u32 reset_counter = 0;
+    bool reset_enabled = true;
+};
+
+} // namespace InputCommon