Detection Thresholds for Vertical Gains in VR and Drone-Based Telepresence Systems
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2020 IEEE Conference on Virtual Reality and 3D User Interfaces (VR) Detection Thresholds for Vertical Gains in VR and Drone-based Telepresence Systems Keigo Matsumoto* Eike Langbehn† Takuji Narumi‡ Frank Steinicke§ Cyber Interface Lab. Human-Computer Interaction Cyber Interface Lab. Human-Computer Interaction The University of Tokyo University of Hamburg The University of Tokyo University of Hamburg Figure 1: Illustration of the concept of a drone-based telepresence system using a vertical gain: (left) the user wears a virtual reality head-mounted display (HMD) moving in the local environment (LE), (center) the drone-based telepresence system in the remote environment (RE), and (right) the users view of the RE on the HMD. ABSTRACT 1INTRODUCTION Several redirected walking techniques have been introduced and ana- There was a great progression in the field and market of drones over lyzed in recent years, while the main focus was on manipulations in the past years. In particular, the evolution of commercial drones horizontal directions, in particular, by means of curvature, rotation, has progressed rapidly; a drone equipped with advanced attitude and translation gains. However, less research has been conducted control and a camera can be purchased from $ 100. There are many on the manipulation of vertical movements and its possible use as a possibilities for these commercial drones, and one of them is the redirection technique. Actually, vertical movements are fundamen- usage as telepresence drone system. Unlike other telepresence robots, tally important, e.g., for remotely steering a drone using a virtual telepresence drones can move freely in 3D space, in particular, they reality headset. can move vertically, and therefore telepresence drones can execute a In this paper, we explored vertical gains, a novel redirection wide range of tasks, such as telecommunications [3, 31], sports [10], technique, which enables us to purposefully manipulate the mapping and remote operations [30]. For instance, drones are already used of the user’s physical vertical movements to movements in the virtual to inspect bridges and buildings, and in such situations, dynamic space and the remote space. This approach allows natural and more vertical movement and precise movement are important [12]. active physical control of a real drone. To demonstrate the usability However, due to their ability to move in 3D space, drones are of vertical gains, we implemented a telepresence drone and vertical typically harder to operate than their 2D counterparts such as mobile redirection techniques for stretching and crouching actions using robots. Currently, many drones are controlled by handheld devices, common VR devices. We conducted two user studies to investigate especially joysticks, while the user wears a virtual reality (VR) head- the effective manipulation ranges and its usability: one study using mounted display (HMD) in the local environment (LE) to see the a virtual environment (VE), and one using a camera stream from a remote environment (RE). Such devices are not easy to operate, and telepresence drone. The results revealed that our technique could it requires a longer training before users can precisely control and manipulate a users vertical movement without her/his noticing. steer a drone. Keywords: In previous studies, methods of manipulating the drone using Drone, Vertical movement, Redirection, Telepresence the user’s body movement were introduced and demonstrated their Index Terms: H.5.1 [Multimedia Information Systems]: Artificial, effectiveness [7,9]. Although, real body movements provide users augmented, and virtual realities— with a high subjective sense of presence in a remote place, ascent and descent in flight are constrained by the range of the human *e-mail: [email protected] vertical movement; therefore, one of our goal was to control the †e-mail: [email protected] drone with only small body movements while maintaining a natural ‡e-mail: [email protected] sense of movement. On the other hand, high precision movements §e-mail: [email protected] may be required on-site, such as safety inspections. Hence, another our goal was to control the movement of the drone more finely than our actual body movement. It is also important to avoid VR sickness when performing those operations. As a technique to manipulate the movement of a telepresence 2642-5254/20/$31.00 ©2020 IEEE 101 DOI 10.1109/VR46266.2020.00-76 robot while maintaining natural user movements, redirected walking (RDW) is proposed [24, 33, 34]. In the field of RDW, manipulations in horizontal directions have been in focus, e.g., translation, rotation, curvature, and bending gains [16,23,27,28]. However, for operating drones, the vertical movement is fundamentally important, and few research projects in the RDW field addressed vertical movements [6, 21, 22]. In this paper, we explore vertical gains, a novel redirection tech- nique, which enables us to purposefully manipulate the mapping of the user’s physical vertical movements to movements in the virtual space. This is intended to allow natural and more active physical control of a drone. With this technique, the users physical movement distances while stretching and crouching in VR are intentionally Figure 2: Overview of experiment 1: (left) a user wears a virtual reality expanded or contracted by the system using certain gains that deter- head-mounted display (HMD) and crouches in the local environment mine the mapping between physical and virtual/remote movements. (LE), (center) another user wears a virtual reality HMD and stretches To demonstrate the possibilities afforded by vertical gains, we im- walking in the LE, and (right) the user’s view of the VE on the HMD. plemented a telepresence drone and vertical redirection techniques for stretching and crouching actions using standard VR devices. We conducted two user studies to investigate the manipulation ranges perform yaw rotation and translational movement at the same time, where users do not notify the manipulation. Although, we could also the posture may become uneasy. In this way, the freedom of drones use noticeable manipulations, these might have side effects such as is limited to some extent. Commercial drones are often used for VR sickness. Hence, there is a need for detection thresholds of verti- photographs and entertainment but are sometimes used for education cal movement manipulation. The results revealed that our methods [15], haptic, and tactile presentation [1, 2], and telepresence systems could manipulate a users vertical movement with a gain larger than [7]. The most popular way to control drone is by using a controller the conventional translation gain in the fore-aft direction without with joysticks, but there are other methods for manipulating the her/his noticing. That means that the drone would perform more drone by gaze [5] or head movement [7, 9]. intense vertical movement than the user in the real world without noticing the manipulation. 2.2 Telepresence drone systems In this paper, we focus on two basic vertical movements, i.e., (i) A telepresence drone can conduct a wide range of tasks including stretching and (ii) crouching. We investigate how much manipulation telecommunications [3, 31], remote operations [30], entertainment is noticeable in (1) a virtual environment (VE) and (2) in a RE of [8], sports [10], and safety inspections [12]. In such a system, not a telepresence drone system. The reason for investigating the VE only the presentation of RE but also natural and intuitive operation in addition the RE is that it is known that depth perception in VEs is important. Several studies have examined user movement as a and real space significantly differ [11]. Further differences can be potential input for interaction with telepresence drones. Higuchi and found in different viewing angles and latency. The results of these Rekimoto presented Flying Head, which synchronizes the user’s experiments provide the basis for future immersive telepresence head motions with the movements of a drone, and can be easily drone systems in which users can naturally elevate to explore remote manipulated with motions such as walking, looking around, and places using a small movement while maintaining a natural sense of crouching [7, 9]. They tried one-to-one-mapping, which means movement. that the amount of drone movement is the same amount of user The contributions of this work are summarized in the following movement, and one-to-two-mapping, which means if the user moves three points: 1 m, the drone moves 2 m, but in their work did not care whether the • We proposed a vertical gain for various vertical movements user is aware of these operations. such as stretching and crouching. 2.3 Redirected Walking • We measured detection thresholds for vertical gains in a VE Redirected walking (RDW) is a technique that manipulates a users and RE. spatial perception of the horizontal direction by viewpoint manipu- • We investigated the effects of latency and viewing angle on lation [24]. By using this technique, it is possible to compress vast vertical gains by comparing the results obtained with VE and VEs into a smaller real space. One of the most fundamental RDW RE. techniques is translation gain. Translation gain gT is defined as follow 2RELATED WORK dvirtual gT = (1) In considering the introduction of redirection to the telepresence dreal drone system, in this section, we describe drones, telepresence sys- where translation movement distance is d and simulated trans- tems, and redirected walking. real lation movement distance dvirtual. For example, when a user is = 2.1 Drones walking forward 1 m with gain gT 2, the user experiences 2 m of forwarding movement in the VE. Unmanned aerial vehicles (UAVs) or drones have been developed In the RDW field, a lot of research projects have been done for military use, but in recent years various commercial drones have on horizontal movement [16, 17, 20, 29]; however, there are few become popular.