Implementation of elbow model for the controller position and rotation.

chrome/browser/android/vr_shell/elbow_model.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Adapted from:
+// https://github.com/googlevr/gvr-unity-sdk/blob/master/Samples/DaydreamLabsControllerPlayground/Assets/GoogleVR/Scripts/Controller/GvrArmModel.cs
+
+#ifndef CHROME_BROWSER_ANDROID_VR_SHELL_ELBOW_MODEL_H_
+#define CHROME_BROWSER_ANDROID_VR_SHELL_ELBOW_MODEL_H_
+
+#include "third_party/gvr-android-sdk/src/libraries/headers/vr/gvr/capi/include/gvr_types.h"
+
+namespace vr_shell {
+
+class ElbowModel {
+ public:
+  struct UpdateData {
+    bool connected;
+    gvr::Quatf orientation;
+    gvr::Vec3f gyro;
+    gvr::Vec3f head_direction;
+    float delta_time_seconds;
+  };
+
+  explicit ElbowModel(
+      gvr_controller_handedness handedness = GVR_CONTROLLER_RIGHT_HANDED);

[cjgrant, 2017/04/03 19:24:59]

I think use of default arguments is generally discouraged.  Can probably skip it
here.

[acondor_, 2017/04/19 18:44:27]

Done.

+  ~ElbowModel();
+
+  const gvr::Vec3f& GetControllerPosition() const { return wrist_position_; }
+  const gvr::Quatf& GetControllerRotation() const { return wrist_rotation_; }
+  float GetAlphaValue() const { return alpha_value_; }
+
+  void Update(const UpdateData& update);
+
+ private:
+  void UpdateHandedness();
+  void UpdateTorsoDirection(const UpdateData& update);
+  void ApplyArmModel(const UpdateData& update);
+  void UpdateTransparency(const UpdateData& update);
+
+  gvr_controller_handedness handedness_;
+
+  gvr::Vec3f wrist_position_;
+  gvr::Quatf wrist_rotation_;
+  float alpha_value_;
+
+  gvr::Vec3f elbow_position_;
+  gvr::Quatf elbow_rotation_;
+  gvr::Vec3f shoulder_position_;
+  gvr::Quatf shoulder_rotation_;
+  gvr::Vec3f torso_direction_;
+  gvr::Vec3f handed_multiplier_;
+};
+
+}  // namespace vr_shell
+
+#endif  // CHROME_BROWSER_ANDROID_VR_SHELL_ELBOW_MODEL_H_