Modern Virtual Reality (VR) technology has enabled users to experience Real Environment (RE) sports in their homes. For VR table tennis, one of the most popular VR sports, the players have rankings and tournaments and compete for RE awards. Based on this phenomenon, this paper aims to understand the benefits of RE training in improving VR table tennis skills. In a user study with 12 novice table tennis players, we measured their performance in 16 basic skills via a pre- and post-study design using a novel training protocol designed for both RE and VR players. We also asked participants for their insights into the training and to evaluate their experience. Our results show a significant improvement in all measured skills. However, participants identified issues with the technology that caused discomfort. Our findings provide valuable insights for software developers working on VR sports applications, enabling them to create better experiences for VR table tennis players. They can also help developers of VR training applications identify areas for improvement with the current technology.

Previous work hypothesized that for Virtual Reality (VR) and Augmented Reality (AR) displays a mismatch between disparities and optical focus cues, known as the vergence and accommodation conflict (VAC), affects depth perception and thus limits user performance in 3D selection tasks within arm’s reach (peri-personal space). To investigate this question, we built a multifocal stereo display, which can eliminate the influence of the VAC for pointing within the investigated distances. In a user study, participants performed a virtual hand 3D selection task with targets arranged laterally or along the line of sight, with and without a change in visual depth, in display conditions with and without the VAC. Our results show that the VAC influences 3D selection performance in common VR and AR stereo displays and that multifocal displays have a positive effect on 3D selection performance with a virtual hand.

Although precise 3D positioning is not always necessary in virtual environments, it is still an important task for current and future applications of Virtual Reality (VR), including 3D modelling, engineering, and scientific applications. We focus on 3D positioning techniques in immersive environments that use a 6DOF controller as input device and present a new technique that improves 3D positioning performance in VR, in both speed and accuracy. Towards this goal, we adapted an extended sliding technique to VR systems with a controller as input device and compared it with previously presented 3DOF positioning techniques. The results showed that our new Extended VR Sliding technique significantly improved the accuracy for 3D positioning tasks, especially for targets in contact with the scene.

Moving objects is an important task in 3D user interfaces. In this work, we focus on (precise) 3D object positioning in immersive virtual reality systems, especially head-mounted displays (HMDs). To evaluate input method performance for 3D positioning, we focus on an existing sliding algorithm, in which objects slide on any contact surface. Sliding enables rapid positioning of objects in 3D scenes on a desktop system but is yet to be evaluated in an immersive system. We performed a user study that compared the efficiency and accuracy of different input methods (mouse, hand-tracking, and trackpad) and cursor display conditions (stereo cursor and one-eyed cursor) for 3D positioning tasks with the HTC Vive. The results showed that the mouse outperformed hand-tracking and the trackpad, in terms of efficiency and accuracy. Stereo cursor and one-eyed cursor did not demonstrate a significant difference in performance, yet the stereo cursor condition was rated more favourable. For situations where the user is seated in immersive VR, the mouse is thus still the best input device for precise 3D positioning.

Constrained interaction and navigation methods for virtual reality reduce the complexity of the interaction. Yet, with previously presented solutions, users need to learn new interaction tools or remember different actions for changing between different interaction methods. In this paper, we propose Fluid VR, a new 3D user interface for interactive virtual environments that lets users seamlessly transition between navigation and selection. Based on the selected object's properties, Fluid VR applies specific constraints to the interaction or navigation associated with the object. This way users have a better control of their actions, without having to change tools or activate different modes of interaction.

We augment 3D user interfaces with a new technique that enables users to select objects that are invisible from the current viewpoint. We present a layer-based method for selecting invisible objects, which works for arbitrary objects and scenes. The user study shows that with our new techniques users can easily select hidden objects.