Martin Kraus

A comparison of head-mounted and hand-held displays for 360° videos with focus on attitude and behavior change

The present study is designed to test how immersion, presence, and narrative content (with a focus on emotional immersion) can affect ones pro-environmental attitude and behavior with specific interest in 360° videos and meat consumption as a non pro-environmental behavior. This research describes a between-group design experiment that compares two systems with different levels of immersion and two types of narratives, one with and one without emotional content. In the immersive video (IV) condition (high immersion), 21 participants used a Head-Mounted Display (HMD) to watch an emotional 360° video about meat consumption and its effects on the environment; another 21 participants experienced the tablet condition (low immersion) where they viewed the same video but with a 10.1 inch tablet; 22 participants in the control condition viewed a non emotional video about submarines with an HMD. The purpose of the experiment was to test the effect of presence and emotional impact on pro-environmental attitude and behavior. In a questionnaire, self-reported measurements were used to address presence, emotional impact and pro-environmental attitude, while an unobtrusive method evaluated pro-environmental behavior. The results showed that both immersion and emotional impact enhance self-reported presence; higher immersion and emotional impact enhanced pro-environmental attitude; narrative content and emotional immersion (i.e., personal attachment to the characters) enhanced pro-environmental behavior. Higher immersion appeared to increase pro-environmental behavior but not significantly.

Stereoscopic augmented reality system for supervised training on minimal invasive surgery robots

Training in the use of robot-assisted surgery systems is necessary before a surgeon is able to perform procedures using these systems because the setup is very different from manual procedures. In addition, surgery robots are highly expensive to both acquire and maintain --- thereby entailing the need for efficient training. When training with the robot, the communication between the trainer and the trainee is limited, since the trainee often cannot see the trainer. To overcome this issue, this paper proposes an Augmented Reality (AR) system where the trainer is controlling two virtual robotic arms. These arms are virtually superimposed on the video feed to the trainee, and can therefore be used to demonstrate and perform various tasks for the trainee. Furthermore, the trainer is presented with a 3D image through a stereoscopic display. Because of the added depth perception, this enables the trainer to better guide and help the trainee. A prototype has been developed using low-cost materials and the system has been evaluated by surgeons at Aalborg University Hospital. User feedback indicated that a 3D display for the trainer is very useful as it enables the trainer to better monitor the procedure, and thereby enhances the training experience. The virtual overlay was also found to work as a good and illustrative approach for enhanced communication. However, the delay of the prototype made it difficult to use for actual training.

Practical Implementation of a Graphics Turing Test

We present a practical implementation of a variation of the Turing Test for realistic computer graphics. The test determines whether virtual representations of objects appear as real as genuine objects. Two experiments were conducted wherein a real object and a similar virtual object is presented to test subjects under specific restrictions. A criterion for passing the test is presented based on the probability for the subjects to be unable to recognise a computer generated object as virtual. The experiments show that the specific setup can be used to determine the quality of virtual reality graphics. Based on the results from these experiments, future versions of the Graphics Turing Test could ease the restrictions currently necessary in order to test object telepresence under more general conditions. Furthermore, the test could be used to determine the minimum requirements to achieve object telepresence.

Initial Exploration of the Use of Specific Tangible Widgets for Tablet Games

In this paper we investigated the use of tangible widgets vs. the use of finger touch for tablet games, which to our knowledge has not been researched so far. A user test was conducted where participants would report which of the two interaction methods they preferred for playing two tablet games: a fast-paced and a slow-paced game. We conclude that some of the participants found tangible widgets to be an interesting and potentially entertaining interaction method, even though our implementation had technical shortcomings compared to finger touch. Further study is needed to investigate how to fix these shortcomings, and how to increase the game experience of tablet games using tangible widgets.

Visualizing Contour Trees within Histograms

Many of the topological features of the isosurfaces of a scalar volume field can be compactly represented by its contour tree. Unfortunately, the contour trees of most realworld volume data sets are too complex to be visualized by dot-and-line diagrams. Therefore, we propose a new visualization that is suitable for large contour trees and efficiently conveys the topological structure of the most important isosurface components. This visualization is integrated into a histogram of the volume data; thus, it offers strictly more information than a traditional histogram. We present algorithms to automatically compute the graph layout and to calculate appropriate approximations of the contour tree and the surface area of the relevant isosurface components. The benefits of this new visualization are demonstrated with the help of several publicly available volume data sets.

Extending the human body in virtual reality: effect of sensory feedback on agency and ownership of virtual wings

Understanding how users can extend their bodies to control avatars can help to make the avatar control and interaction more intuitive and engaging. This paper investigates how multisensory stimuli in a virtual reality environment can contribute to the experience of owning and controlling an extended humanoid avatar with a set of virtual wings. We tested three conditions: visuomotor stimuli, visuomotor and visuotactile stimuli combined and a control condition with only visuoproprioceptive feedback. Results show that visuo-motor feedback was necessary for establishing agency and body-ownership of the wings, and also proved to be better for task performance than in combination with visuotactile feedback. Visuotactile feedback, on the other hand, significantly enhanced body-ownership of the wings, and agency according to questionnaire ratings.

An affordable virtual reality system for treatment of phantom limb pain

This paper describes the implementation of an affordable phantom limb pain (PLP) home treatment system using virtual reality (VR) and a motion sensor to immerse the users in a virtual environment (VE). The work is inspired by mirror therapy (MT) which is used to treat patients with PLP. This project focuses on phantom pain in amputees. Using a motion sensor, the system tracks the movement of a users hand and translates it onto the virtual hand. The system consists of exercises focusing on opening and closing the hand, rotating the hand, and finer finger movements. These exercises are conveyed in the VR as three games: (1) A bending game, where the patients have to bend a rod, (2) a box game where the patients pick up and place boxes with their hands, (3) and a button memory game where the patients have to push buttons in a given sequence. These games were tested on twelve healthy participants to see if the games encouraged similar movements as in MT. Prior to the experiment a preliminary test was conducted on an amputee with PLP to gather qualitative feedback from an end-user. The results indicated that the games did convey the exercises from the MT, although further testing is needed.

Reviving Aggersborg: Conveying lost heritage sites through indirect augmented reality

This paper propose a simple and user friendly method for aligning an Indirect Augmented Reality application with the real world. Augmented Reality is often considered an innovative platform for conveying cultural heritage, as well as for many other uses. In cases where an Augmented Reality system relies on the internal sensors of mobile devices for orientating its orientation, it will suffer from any inherent issues these sensors may have. An important aspect of Augmented Reality is the alignment with the real world, and since compass sensors of mobile devices are often unreliable, and gyroscopes generally do not have absolute information of real world directions, correct alignment can pose a substantial challenge. The method proposed in this paper, while simple in nature, is based on aligning a gyroscope by pointing it towards a known feature from a known position. The developed application was evaluated through user interaction, expert feedback, and the alignment method through a technical test. The interface was considered simple and intuitive, and the technical test demonstrated the proposed method as a viable way of aligning an Indirect Augmented Reality application to the real world.

Measuring the Latency of an Augmented Reality System for Robot-assisted Minimally Invasive Surgery.

Minimal latency is important for augmented reality systems and teleoperation interfaces as even small increases in latency can affect user performance. Previously, we have developed an augmented reality system that can overlay stereoscopic video streams with computer graphics in order to improve visual communication in training for robot-assisted minimally invasive surgery with da Vinci surgical systems. To make sure that our augmented reality system provides the best possible user experience, we investigated the video latency of the da Vinci surgical system and how the components of our system affect the overall latency. To measure the photon-to-photon latency, we used a microcontroller to determine the time between the activation of a lightemitting diode in front of the endoscopic camera and the corresponding increase in intensity of the surgeon’s display as measured by a phototransistor. The latency of the da Vinci S surgical system was on average 62 ms. None of the components of our overlay system (separately or combined) significantly affected the latency. However, the latency of the assistant’s monitor increased by 14 ms. Passing the video streams through CPU or GPU memory increased the latency to 147 ms and 256 ms, respectively.

Light Field Rendering for Head Mounted Displays using Pixel Reprojection

Light field displays have advantages over traditional stereoscopic head mounted displays, for example, because they can overcome the vergence-accommodation conflict. However, rendering light fields can be a heavy task for computers due to the number of images that have to be rendered. Since much of the information of the different images is redundant, we use pixel reprojection from the corner cameras to compute the remaining images in the light field. We compare the reprojected images with directly rendered images in a user test. In most cases, the users were unable to distinguish the images. In extreme cases, the reprojection approach is not capable of creating the light field. We conclude that pixel reprojection is a feasible method for rendering light fields as far as quality of perspective and diffuse shading is concerned, but render time needs to be reduced to make the method practical.