Virtual Transportation for Immersive Systems

I. INTRODUCTION Computer games have since long explored ways of inducing the notion of traveling or moving along the game scenarios, because it make them much more attractive to people, than static ones. Even in a relatively small scenario it is more attractive to the player being able to become an active observer, than seeing, eventually several animated characters, from a fixed pose. This is the main reason why the Virtual Reality (VR) concept has received so much attention, as being based on the creation of first person views, the user is supposed to be able to actively explore the virtual environment. In usual games viewed via a computer screen, the viewpoint motion has been explored to create first person viewing experiences, but as these tend to induce motion sickness there are always alternative views like bird’s eye views, or follower views. First person views are more used in piloting or driving situations, where a cockpit, or car structure are used to create views from the inside of the plane, or car, through a wind shield. For the driving case, the observer may execute small moves with respect to the car, but it is the car that moves with respect to the world, and the latter movements become much more important than the former ones. On another side, when using a head mounted display (HMD), the observation point is much more egocentric, and either we create the virtual cockpit sensation [1], or the perceived movements should be exactly related with the ones that the observer intentionally executes, in order to avoid cybersickness effects. From previous studies we found that in VR, people start to feel nauseous in certain situations, namely when a motion of a scene is presented while the user is standing still. This occurs because of a disparity relation between our visual and vestibular system, as the first perceives movement on the scene but the second perceived information is that our body is not physically moving [2]. With this in mind, we have been searching for solutions to support navigation VR scenarios in order to take full advantage of its capabilities, while trying to avoid any type of induced discomfort. II. NATURAL MOTION IN VR Walking is the most natural way for humans to move and as such it is expectable as to use it to support locomotion in VR. Although until recently it was hard (or very expensive) to capture the user’s walking motion to use it in to create corresponding sensation inside a VR system, recently introduced tracking systems have brought as very interesting (and low cost) solutions. Using them, it is possible to have users walking along virtual environments. This possibility, although being very interesting, has serious limitations to its use, which arise from the length of HMD cables used by most systems and that limit the extent of the motion, and the possible presence of physical obstacles, like walls, furniture, or people, that unless have a corresponding representation inside the VR worlds may lead to unexpected collisions with the possible consequent injuries. The ideal would be therefore to enable the user to walk and have that fully captured and mapped into the VR envirnment, but without physically moving and thus without any problem with cable lengths or obstacles. The Omni platform was recently introduced with the purpose of enabling the user to literally walk in a VR world. Here, the user being fixed on top of the platform by an harness and using special shoes, can walk on the platform, being his steps translated into the corresponding displacements in the VR environment. But humans have developed transportation systems, to increase traveling velocities and/or reduce the efforts, especially for long distance/duration motions. By consequence, and for the sake of realism, it is natural that similar experiences are to be brought into immersive systems. By consequence it is quite natural to use devices that aim at replicating the sensations of driving a car, piloting a plane, or other, but also others that will create new experiences. As examples there are some recent devices that have been proposed for VR interaction, like Icaros [3] and Birdly [4] which were designed to create bird-like flying experiences. This work presents another solution for enabling user realistic control of displacements in a VR system. Aiming to provide the user with tools that allow him to navigate through endless virtual environments without feeling motion sickness. III. APPARATUS Observing the world with our focus on travelling mechanisms, we could identify situations where information captured from visual and vestibular system doesn’t match and in general people don’t feel nauseous, such as driving a vehicle or riding a bicycle. Our hypothesis is that if device can be used to enable us to sense some the movement effects in a way that we can anticipate or control the movement coupled with visual cues we will not experience motion sickness. A. Developed Platform To achieve our goal we developed a system based on the control mechanics of a SegwayTM. It is composed by a rotating platform with a handlebar and steering bar. Tilting the handle bar left or right will rotate the platform and the virtual view accordingly, while tilting front and back will produce a small vibration on the platform and move forward and backward in the virtual environment. For the visual system we are using the Head Mounted Display (HMD) Oculus Rift DK2 (Fig. 1). B. Virtual Environment To demonstrate and test the system we build a virtual environment with some obstacles where the user can experience our proposed locomotion mechanism (Fig. 2). Using the developed platform and the tracking system of Oculus Rift DK2 (including the camera) the user is able to freely move and look around the virtual scene. C. Physiological Data In order to better understand what users are feeling while using the system we keep track of their physiological activity, such as Electrocardiography (ECG), Electrodermal Activity (EDA), Body Acceleration (BA) and Body Temperature (BT), for later process and analysis. The bio-signals data collecting device used was the BiTalino, a low cost toolkit especially designed for this propose. This opens the possibility of using such data for automatically detect user discomfort through the analysis if variations in some of the parameters. IV. CONCLUSION This demonstration aims at showing that cyber-sickness can be reduced by the use of a system capable to provide the right motion feedback to user. It simulates all the movements in the virtual environment (e.g. Segway mechanics) providing a synchronous relation between visual and vestibular systems. The instructions for building the necessary setup, as well as the software, can be obtained from [5] . REFERENCES [1] J. C. G. Sanchez, B. Patr˜ao, L. Almeida, J. Perez, P. Menezes, J. Dias, and P. Sanz, “Design and evaluation of a natural interface for remote operation of underwater robots,,” IEEE Computer Graphics and Applications, vol. PP, no. 99, 2015. [2] B. Patr˜ao, S. N. Pedro, and P. Menezes, “How to deal with virtual reality sickness,” in EPCGI’2015: The 22nd Portuguese Conf. on Computer Graphics and Interaction, Coimbra, Portugal, 2015. [3] Icaros Team, “Icaros.” [Online]. Available: http://www.icaros.net/ [4] Somniacs, “Birdly.” [Online]. Available: http://www.somniacs.co/ [5] P. Menezes et al. Learn ar/vr related subjects. [Online]. Available: http://orion.isr.uc.pt/index.php/arvr