Current Virtual Reality systems are designed for interaction under visual control. Using built-in cameras, headsets track the user's hands or hand-held controllers while they are inside the field of view. Current systems thus ignore the user's interaction with off-screen content -- virtual objects that the user could quickly access through proprioception without requiring laborious head motions to bring them into focus. In this paper, we present HOOV, a wrist-worn sensing method that allows VR users to interact with objects outside their field of view. Based on the signals of a single wrist-worn inertial sensor, HOOV continuously estimates the user's hand position in 3-space to complement the headset's tracking as the hands leave the tracking range. Our novel data-driven method predicts hand positions and trajectories from just the continuous estimation of hand orientation, which by itself is stable based solely on inertial observations. Our inertial sensing simultaneously detects finger pinching to register off-screen selection events, confirms them using a haptic actuator inside our wrist device, and thus allows users to select, grab, and drop virtual content. We compared HOOV's performance with a camera-based optical motion capture system in two folds. In the first evaluation, participants interacted based on tracking information from the motion capture system to assess the accuracy of their proprioceptive input, whereas in the second, they interacted based on HOOV's real-time estimations. We found that HOOV's target-agnostic estimations had a mean tracking error of 7.7 cm, which allowed participants to reliably access virtual objects around their body without first bringing them into focus. We demonstrate several applications that leverage the larger input space HOOV opens up for quick proprioceptive interaction, and conclude by discussing the potential of our technique.

翻译：摘要：当前虚拟现实系统设计旨在视觉控制下进行交互。利用内置摄像头，头戴设备可在用户双手或手持控制器处于视野范围内时进行追踪。然而现有系统忽略了用户与屏幕外内容的交互——这些用户可通过本体感觉快速访问的虚拟对象，无需进行繁琐的头部运动将其纳入视野中心。本文提出HOOV腕戴式传感方法，使VR用户能够与视域外对象进行交互。基于单个腕戴式惯性传感器的信号，HOOV持续估算用户手部在三维空间中的位置，在双手脱离头戴设备追踪范围时补充追踪能力。我们提出的新颖数据驱动方法仅通过连续估算手部朝向即可预测手部位置与运动轨迹，而该朝向本身即可基于惯性观测数据稳定获取。该惯性传感系统同步检测手指捏合动作以记录视域外选择事件，并通过腕戴装置内的触觉执行器进行确认，从而允许用户完成虚拟内容的选取、抓取与放置操作。我们通过两方面实验将HOOV性能与基于摄像机的光学动作捕捉系统进行对比：首次评估中，参与者根据动捕系统追踪信息进行交互以检验其本体感输入的精度；第二次评估中，参与者依据HOOV的实时估算进行交互。实验发现，HOOV与目标无关的估算平均追踪误差为7.7厘米，使得参与者能够可靠地访问身体周围的虚拟物体，而无需预先将其纳入视野中心。我们展示了若干利用HOOV开辟更大输入空间以实现快速本体感交互的应用，并最终讨论了该技术的潜在价值。