Measuring Vection in a Large Screen Virtual Environment

This paper describes the use of a large screen virtual environment to induce the perception of translational and rotational self-motion. We explore two aspects of this problem. Our first study investigates how the level of visual immersion (seeing a reference frame) affects subjective measures of vection. For visual patterns consistent with translation, self-reported subjective measures of self-motion were increased when the floor and ceiling were visible outside of the projection area. When the visual patterns indicated rotation, the strength of the subjective experience of circular vection was unaffected by whether or not the floor and ceiling were visible. We also found that circular vection induced by the large screen display was reported subjectively more compelling than translational vection. The second study we present describes a novel way in which to measure the effects of displays intended to produce a sense of vection. It is known that people unintentionally drift forward if asked to run in place while blindfolded and that adaptations involving perceived linear self-motion can change the rate of drift. We showed for the first time that there is a lateral drift following perceived rotational self-motion and we added to the empirical data associated with the drift effect for translational self-motion by exploring the condition in which the only self-motion cues are visual

Visualization and (Mis)Perceptions in Virtual Reality

Virtual Reality (VR) technologies are now being widely adopted for use in areas as diverse as surgical and military training, architectural design, driving and flight simulation, psychotherapy, and gaming/entertainment. A large range of visual displays (from desktop monitors and head-mounted displays (HMDs) to large projection systems) are all currently being employed where each display technology offers unique advantages as well as disadvantages. In addition to technical considerations involved in choosing a VR interface, it is also critical to consider perceptual and psychophysical factors concerned with visual displays. It is now widely recognized that perceptual judgments of particular spatial properties are different in VR than in the real world. In this paper, we will provide a brief overview of what is currently known about the kinds of perceptual errors that can be observed in virtual environments (VEs). Subsequently we will outline the advantages and disadvantages of particular visual displays by foc using on the perceptual and behavioral constraints that are relevant for each. Overall, the main objective of this paper is to highlight the importance of understanding perceptual issues when evaluating different types of visual simulation in VEs

Gait parameters while walking in a head-mounted display virtual environment and the real world

Full-body motion tracking data was collected for six subjects during free walking. Each participant was asked to walk to a previously seen target under four experimental conditions: eyes closed within the real world, eyes closed wearing a head-mounted display (HMD), eyes open in the real world, and eyes open wearing a HMD. We report three gait parameters for each of these four conditions: stride length, walking velocity, and head-trunk angle. This data reveals that these gait parameters within a HMD virtual environment (VE) are different than those in the real world. A person wearing a HMD and backpack walks slower, and takes a shorter stride length than they do in a comparable real world condition. In addition, head-trunk angle while walking to a target on the ground plane is lowest when walking with eyes open in a HMD VE

The contributions of visual flow and locomotor cues to walked distance estimation in a virtual environment

Traversed distance perception involves estimating the extent of self-motion as one travels from one position in space to another. As such, it is a multi-modal experience in which information from both visual flow and locomotor cues (i.e. proprioceptive, efference copy and vestibular cues) jointly specify the magnitude of self-motion. While recent evidence has demonstrated the extent to which each of these cues can be used independently to estimate traversed distance, relatively little is known about how they are integrated when simultaneously present. Evaluating multi-modal cue integration in the context of dynamic locomotor behaviour is important to both understanding issues related to self-motion perception, as well as perceptual-motor coupling in real and virtual environments

Advanced endoscopic imaging for diagnosis of inflammatory bowel diseases : present and future perspectives

Crohn's disease and ulcerative colitis are chronic inflammatory bowel diseases (IBD) causing severe damage of the luminal gastrointestinal tract. Differential diagnosis between both disease entities is sometimes awkward requiring a multifactorial pathway, including clinical and laboratory data, radiological findings, histopathology and endoscopy. Apart from disease diagnosis, endoscopy in IBD plays a major role in prediction of disease severity and extent (i.e. mucosal healing) for tailored patient management and for screening of colitis-associated cancer and its precursor lesions. In this state-of-the-art review, we focus on current applications of endoscopy for diagnosis and surveillance of IBD. Moreover, we will discuss the latest guidelines on surveillance and provide an overview of the most recent developments in the field of endoscopic imaging and IBD