# \"Blurry Touch Finger\": Touch-Based Interaction for Mobile Virtual Reality with Clip-on Lenses
## 1 Introduction  
Mobile virtual reality (M-VR) loosely refers to the immersive content platforms that are based on the smartphone [1]. M-VR in its typical form uses a head-set, into which the smartphone is inserted to lend its display (see Figure 1, left). The head-set itself only provides the display optics, simple interaction device (e.g., button or touch pad) and world isolation [2, 3]. M-VR is often contrasted with the higher-end (and priced) PC based VR (PC-VR) in which the display integrated head-set is separated from and tethered to a PC [4, 5]. M-VR is generally regarded, aside from being mobile and self-contained, more convenient, inexpensive, and targeted for casual use. Nevertheless, M-VR in such a typical form is still not sufficient for a wide adoption by the public mass; the head-set is still somewhat bulky, interaction methods awkward and the ever-needed and must-be-handy smartphone becomes inaccessible during when used for VR (after the insertion). Recently, a new breed of M-VR, as called \"EasyVR,\" has appeared in the market in the form of flipping or clipping a cheap non-isolating magnifying lenses on the smartphone (see Figure 1, right). Surprisingly, despite being open and the user's peripheral view not shut from the outside world, such a display configuration still gives a good level of immersion with the magnified view covering much of the human's field of view [6]. Given its much-improved convenience and the advantage of quick setting, it serves as a viable alternative configuration for M-VR (there is even a fold-out version built-into the smartphone case [7]). The open configuration also makes the immediate switch to the regular smartphone mode quite possible and vice versa (e.g., switch between VR and texting, see Figure 2). One of the most important elements that makes \"EasyVR\" easy is perhaps the possibility of using the touch screen for interaction. Conventional M-VR set-ups have offered the head-direction (or gaze) and touch pad (or button) on the side of the head-set for the lack of any better method. The use of the touch screen in EasyVR brings about: (1) the usual and familiar touch based user experience (including the swipe and flick), (2) natural bimanual interaction, and thereby, (3) more direct and efficient interaction, and (4) no need for an additional interaction device. Even though the open set-up allows the fingers to touch and manipulate objects on the touch screen, they are seen through the magnifying lens. While the virtual objects will be seen in focus by design, the fingers are not and seen blurry by the binocular rivalry. Interestingly, this very feature makes the target object visible and thereby the touch screen interaction feasible. This also partly solves the so called \"fat finger\" problem in touch based smartphone interaction (see Section 3 for more details) [8]. In this paper, we explore this idea of the touch screen based interaction for EasyVR, called the \"Blurry Touch Finger (BTF)\" (see Figure 3). We carried out the first stage basic usability evaluation to validate the proposed idea: whether the EasyVR user can in fact select virtual objects accurately using BTF, compared to e.g., the conventional interaction techniques. The evaluation through the performance of object selection, which is one of the most important and basic interactive VR task [9], would provide a good yardstick for the practicality and feasibility of EasyVR and the associated \"Blurry Touch Finger\" method. Figure 1: Typical mobile virtual reality with the smartphone inserted and closed into an inexpensive headset (**left**), and “EasyVR” in which light magnifying lenses are clipped on the smartphone in a non-isolating way. Figure 2: Main features of “EasyVR”: (1) quick put-on, (2) no inconvenient mounting on the head, (3) seamless switch between regular smartphone and VR modes, (4) touch screen based interaction possible (and no additional interaction devices—self-contained).