Shadow detection for vehicles by locating the object-shadow boundary

We introduce in this paper a shadow detection method for vehicles in traffic video sequences. Our method approximates the boundary between vehicles and their associated shadows by one or more straight lines. These lines are located in the image by exploiting both local information (e.g. statistics in intensity differences) and global information (e.g. principal edge directions). The proposed method does not assume a particular lighting condition, and requires no human interaction nor parameter training. Experiments on practical real-world traffic video sequences demonstrate that our method is simple, robust and efficient under traffic scenes with different lighting conditions. Accurate positioning of target vehicles is thus achieved even in the presence of cast shadows.postprin

Using virtual reality in criminological research

Since the pioneering early studies of the 1990s hinted at its promise as a research method, virtual reality (VR) technology has increasingly been used by social scientists. Given recent developments that have greatly enhanced realism, reduced costs, and increased possibilities for application, VR seems well on its way to become an established research tool in the social sciences. However, as with other ethodological innovations, the field of criminology hasbeen slow to catch on. To address this gap, this article explores the potential of VR as a tool for crime research. It provides readers with a brief and non-technical description of VR and its main elements and reviews severalapplications of VR in social scientific research that are potentially relevant for criminologists. By way of illustration, we identify and discuss in more detail different areas in which we think the field of criminology can particularly benefit from VR and offer suggestions for research. Some of the equipment available on the consumer market is also reviewed.In conjunction, the different sections should equip readers interested in applying VR in their own research with a fundamental understanding of what it entails and how it can be applied

Lag compensation by image deflection and prediction: a review on the potential benefits to virtual training applications for manufacturing industry

An immersive virtual reality system can be used to simulate manufacturing facilities for training purposes. However, time lags can limit the realism of such a simulation. These lags occur when an immersive virtual reality system responds to head and hand movements. Time lags have been shown to degrade the performance of a hand manipulation virtual training task. Lag compensation is, therefore, desirable. This paper highlights the lag problem with virtual training applications and explores potential benefits of an existing lag compensation technique. This lag compensation technique used image deflection and prediction algorithms that were originally developed for virtual reality flight simulation applications

Combined and interacting effects of hand and head movement delays on discrete manual performance in a virtual environment

Transmission delays occur when a virtual environment responds to the hand and head movements of an operator. The effects of hand and head-related delays on discrete manual performance was investigated experimentally and compared. Imposed hand and head-related pure delays equal to or greater than 110 ms and 220 ms, respectively, significantly increased hand Movement Time (MT). The effect of hand-related delays was greater than that of head-related delays of the same magnitude. A regression model describing the combined effects of both delays on MT is reported (R-2 = 0.95). Analyses of the interactions among delays, target width, and distances have shown the need to adopt the traditional classification of delays into (1) control delay, and (2) display delay. The use of this taxonomy and the regression analyses to describe and explain the effects of individual and combined effects of delays on discrete target-reaching task performance in virtual environments are discussed

Quantifying scene movement with 'spatial velocity' and its effects on cybersickness

Viewing wide field-of-view scene movement with a Virtual Reality (VR) display can cause symptoms of cybersickness (e.g., nausea and headache). It has been known that cybersickness is a type of vection-induced motion sickness. Since vection is associated with the perception of moving scene, two studies have been conducted to investigate the effects of different scene movements on levels of cybersickness. The velocity and complexity of the scene movements were quantified by a previously reported metric called 'spatial velocity (SV)' while the levels of cybersickness were measured in terms of nausea ratings and Simulator Sickness Questionnaire (SSQ) scores. Results showed that in both experiments, both the nausea ratings and the SSQ total sickness scores increased significantly with increasing SV in the dominant axes of scene movement. Potential uses of the SV metric for formulating a CyberSickness Dose Value (CSDV) are discussed

Cybersickness in the presence of scene rotational movements along different axes

Compelling scene movements in a virtual reality (VR) system can cause symptoms of motion sickness (i.e., cybersickness). A within-subject experiment has been conducted to investigate the effects of scene oscillations along different axes on the level of cybersickness. Sixteen male participants were exposed to four 20-min VR simulation sessions. The four sessions used the same virtual environment but with scene oscillations along different axes, i.e., pitch, yaw, roll, or no oscillation (speed: 30 degrees /s, range: +/- 60 degrees). Verbal ratings of the level of nausea were taken at 5-min intervals during the sessions and sickness symptoms were also measured before and after the sessions using the Simulator Sickness Questionnaire (SSQ). In the presence of scene oscillation, both nausea ratings and SSQ scores increased at significantly higher rates than with no oscillation. While individual participants exhibited different susceptibilities to nausea associated with VR simulation containing scene oscillations along different rotational axes, the overall effects of axis among our group of 16 randomly selected participants were not significant. The main effects of, and interactions among, scene oscillation, duration, and participants are discussed in the paper. (C) 2001 Elsevier Science Ltd. All rights reserved

Computational Ergonomics - A possible extension of computational neuroscience? Definitions, potential benefits, and a case study on cybersickness

This paper proposes a sub-discipline called 'Computational Ergonomics' and explains how it will support the ultimate goal of 'studying human by building a human through quantitative modeling'. This idea is not new and has been successfully implemented in the sub-discipline of Computational Neuro-Sciences (CNS) for more than 20 years. In fact, quantitative models developed by CNS researchers are becoming comprehensive enough to explain simple voluntary human behavior already. We believe the timing is right for ergonomics researchers to make use of the many open-source quantitative CNS modeling algorithms as fundamental building blocks of quantitative human performance models. This move is also consistent with the new sub-discipline of 'neuroergonomics' (Spring 2003 issue of Theoretical Issues in Ergonomics Sciences) and the call for more quantitative formal models of human performance (Spring 2003 issue of Human Factors). In addition to explaining the essential elements of the proposed 'Computational Ergonomics', this paper presents a case study to illustrate the benefits of the proposed changes. In particular, how the authors' research on simulator sickness with virtual reality systems has benefited from the proposed changes. This paper intends to raise stimulating and controversial arguments to be discussed during the conference presentation

The use of cooper-harper technique to enhance the measurement of rated sense-of-presence in virtual and real environments

A recent study has shown that the Presence Questionnaire (PQ) developed by Singer and Witmer (1996) fail to detect a significant difference between the sense-of-presence reported by participants exposed to a virtual environment (VE) and to its corresponding real environment (RE). Two experiments were conducted to examine the reported failure of PQ and study the benefits of using Cooper-Harper presentation technique. In the first experiment, participants were exposed to a virtual, telematic, and real environment showing similar audio and visual content. In contrary to the literature, the reported PQ total scores reported for the RE condition was significantly higher than that of the VE condition (p<0.05). This suggests that PQ can be a sensitive tool to measure rated sense-of-presence. In the second experiment, the use of Cooper-Harper technique to present PQ yielded mixed benefits. Actual and potential applications of this research include the development of an enhanced PQ that can be used across virtual, telematic, and real environments

Isolating the effects of vection and optokinetic nystagmus on optokinetic rotation-induced motion sickness

Objective: This study investigates isolated effects of vection and optokinetic nystagmus (OKN) on visually induced motion sickness (VIMS) provoked by rotating optokinetic drum patterns. Background: VIMS was the subject of recent standardization activities, but the effects of OKN have not been studied in the absence of vection. Method: Experiment 1 suppressed OKN by eye fixation and examined VIMS severity (both ordinal and ratio scale) and time spent in saturated vection at four pattern rotating velocities of 0, 2, 14, and 34 degrees per second (dps). Experiment 2 suppressed vection by adding a peripheral visual field rotating in the opposite direction to the rotating patterns. VIMS severity and OKN slow-phase velocity were studied at four rotating velocities of 0, 30, 60, and 90 dps. Results: Results from Experiment 1 indicated that VIMS severity increased as the pattern velocity increased from 0 dps to 34 dps. Results from Experiment 2 indicated that as the velocity of the rotating pattern increased, the slow-phase velocity of OKN and the severity of VIMS increased and peaked in the 60-dps condition. In both experiments, ratio-scaled nausea data significantly correlated with ordinal-scaled nausea ratings. Conclusion: VIMS can still occur in the absence of either vection or OKN. Interestingly, the profile of the summed results of the two experiments matches nicely with the profile reported by Hu et al. in which neither OKN nor vection were controlled. Application: Potential applications include modeling and reduction of VIMS in computer gaming environments. Copyright © 2009, Human Factors and Ergonomics Society.published_or_final_versio