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Article Overview

6.2009, 1


The MIRELA framework: modeling and analyzing mixed reality applications using timed automata

VRIC 2008 Special Issue

Jean-Yves Didier et al.

Mixed Reality (MR) aims to link virtual entities with the real world and has many applications such as military and medical ones. In many MR systems and more precisely in augmented scenes, one needs the application to render the virtual part accurately at the right time. To achieve this, such systems acquire data related to the real world from a set of sensors before rendering virtual entities. A suitable system architecture should minimize the delays to keep the overall system delay (also called end-to-end latency) within the requirements for real-time performance. In this context, we propose a compositional modeling framework for MR software architectures in order to specify, simulate and validate formally the time constraints of such systems. Our approach is first based on a functional decomposition of such systems into generic components. The obtained elements as well as their typical interactions give rise to generic representations in terms of timed automata. A whole system is then obtained as a composition of such defined components.

To write specifications, a textual language named MIRELA (MIxed REality LAnguage) is proposed along with the corresponding compilation tools. The generated output contains timed automata in UPPAAL format for simulation and verification of time constraints. These automata may also be used to generate source code skeletons for an implementation on a MR platform.

The approach is illustrated first on a small example. A realistic case study is also developed. It is modeled by several timed automata synchronizing through channels and including a large number of time constraints. Both systems have been simulated in UPPAAL and checked against the required behavioral properties.

[Submitted: June 25th, 2008 | In Peer-Review: July 1st, 2008 | Resubmitted: October 24th, 2008 | Accepted: September 8th, 2008 | Published: April 21st, 2009 ]

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6.2009, 2


Real Walking through Virtual Environments by Redirection Techniques

VRIC 2008 Special Issue

Frank Steinicke et al.

We present redirection techniques that support exploration of large-scale virtual environments (VEs) by means of real walking. We quantify to what degree users can unknowingly be redirected in order to guide them through VEs in which virtual paths differ from the physical paths. We further introduce the concept of dynamic passive haptics by which any number of virtual objects can be mapped to real physical proxy props having similar haptic properties (i. e., size, shape, and surface structure), such that the user can sense these virtual objects by touching their real world counterparts. Dynamic passive haptics provides the user with the illusion of interacting with a desired virtual object by redirecting her to the corresponding proxy prop. We describe the concepts of generic redirected walking and dynamic passive haptics and present experiments in which we have evaluated these concepts. Furthermore, we discuss implications that have been derived from a user study, and we present approaches that derive physical paths which may vary from the virtual counterparts.

[Submitted: July 21st, 2008 | In Peer-Review: July 24th, 2008 | Resubmitted: November 11th, 2008 | Accepted: September 30th, 2008 | Published: April 16th, 2009 ]

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6.2009, 3


Gaze behavior nonlinear dynamics assessed in virtual immersion as a diagnostic index of sexual deviancy: preliminary results

VRIC 2008 Special Issue

Patrice Renaud et al.

This paper presents preliminary results about the use of virtual characters, penile plethysmography and gaze behaviour dynamics to assess deviant sexual preferences. Pedophile patients’ responses are compared to those of non-deviant subjects while they were immersed with virtual characters depicting relevant sexual features.

[Submitted: June 16th, 2008 | In Peer-Review: November 7th, 2008 | Resubmitted: January 8th, 2009 | Accepted: December 12th, 2008 | Published: April 16th, 2009 ]

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6.2009, 4


Transfer of spatial knowledge from a virtual environment to reality: Impact of route complexity and subject’s strategy on the exploration mode

VRIC 2008 Special Issue

Grégory Wallet et al.

The use of virtual reality as tool in the area of spatial cognition raises the question of the quality of learning transfer from a virtual to a real environment. It is first necessary to determine with healthy subjects, the cognitive aids that improve the quality of transfer and the conditions required, especially since virtual reality can be used as effective tool in cognitive rehabilitation. The purpose of this study was to investigate the influence of the exploration mode of virtual environment (Passive vs. Active) according to Route complexity (Simple vs. Complex) on the quality of spatial knowledge transfer in three spatial tasks.

Ninety subjects (45 men and 45 women) participated. Spatial learning was evaluated by Wayfinding, sketch-mapping and picture classification tasks in the context of the Bordeaux district. In the Wayfinding task, results indicated that active learning in a Virtual Environment (VE) increased the performances compared to the passive learning condition, irrespective of the route complexity factor. In the Sketch-mapping task, active learning in a VE helped the subjects to transfer their spatial knowledge from the VE to reality, but only when the route was complex. In the Picture classification task, active learning in a VE when the route was complex did not help the subjects to transfer their spatial knowledge. These results are explained in terms of knowledge levels and frame/strategy of reference.

[Submitted: June 27th, 2008 | In Peer-Review: July 17th, 2008 | Resubmitted: November 10th, 2008 | Accepted: September 18th, 2008 | Published: April 21st, 2009 ]

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6.2009, 5


Spatial audition in a static virtual environment : the role of auditory-visual interaction

VRIC 2008 Special Issue

Khoa-Van Nguyen et al.

The integration of the auditory modality in virtual reality environments is known to promote the sensations of immersion and presence. However it is also known from psychophysics studies that auditory-visual interaction obey to complex rules and that multisensory conflicts may disrupt the adhesion of the participant to the presented virtual scene. It is thus important to measure the accuracy of the auditory spatial cues reproduced by the auditory display and their consistency with the spatial visual cues. This study evaluates auditory localization performances under various unimodal and auditory-visual bimodal conditions in a virtual reality (VR) setup using a stereoscopic display and binaural reproduction over headphones in static conditions. The auditory localization performances observed in the present study are in line with those reported in real conditions, suggesting that VR gives rise to consistent auditory and visual spatial cues. These results validate the use of VR for future psychophysics experiments with auditory and visual stimuli. They also emphasize the importance of a spatially accurate auditory and visual rendering for VR setups.

[Submitted: July 23rd, 2008 | In Peer-Review: July 28th, 2008 | Resubmitted: January 30th, 2009 | Accepted: October 8th, 2008 | Published: April 21st, 2009 ]

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6.2009, 6


Quasi-Convolution Pyramidal Blurring

GRAPP 2008 Special Issue

Martin Kraus

Efficient image blurring techniques based on the pyramid algorithm can be implemented on modern graphics hardware; thus, image blurring with arbitrary blur width is possible in real time even for large images. However, pyramidal blurring methods do not achieve the image quality provided by convolution filters; in particular, the shape of the corresponding filter kernel varies locally, which potentially results in objectionable rendering artifacts. In this work, a new analysis filter is designed that significantly reduces this variation for a particular pyramidal blurring technique. Moreover, the pyramidal blur algorithm is generalized to allow for a continuous variation of the blur width. Furthermore, an efficient implementation for programmable graphics hardware is presented. The proposed method is named “quasi-convolution pyramidal blurring” since the resulting effect is very close to image blurring based on a convolution filter for many applications.

[Submitted: March 7th, 2008 | In Peer-Review: March 12th, 2008 | Resubmitted: August 18th, 2008 | Accepted: July 21st, 2008 | Published: December 11th, 2009 ]

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6.2009, 8


VR Based Visualization and Exploration of Plant Biological Data

VRIC 2008 Special Issue

Wolfram Schoor et al.

This paper investigates the use of virtual reality (VR) technologies to facilitate the analysis of plant biological data in distinctive steps in the application pipeline. Reconstructed three-dimensional biological models (primary polygonal models) transferred to a virtual environment support scientists' collaborative exploration of biological datasets so that they obtain accurate analysis results and uncover information hidden in the data. Examples of the use of virtual reality in practice are provided and a complementary user study was performed.

[Submitted: August 26th, 2008 | In Peer-Review: August 29th, 2008 | Resubmitted: June 19th, 2009 | Accepted: March 9th, 2009 | Published: October 11th, 2010 ]

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6.2009, 9


Haptic visualization of data sets: Exploration of scalar and vector fields

VRIC 2008 Special Issue

Bob Ménélas et al.

Complementary to automatic extraction processes, Virtual Reality technologies provide an adequate framework to integrate human perception in the exploration of large data sets. In such multisensory system, thanks to intuitive interactions, a user can take advantage of all his perceptual abilities in the exploration task. In this context the haptic perception, coupled to visual rendering, has been investigated for the last two decades, with significant achievements. In this paper, we present a survey related to exploitation of the haptic feedback in exploration of large data sets. For each haptic technique introduced, we describe its principles and its effectiveness.

[Submitted: July 22nd, 2008 | In Peer-Review: August 27th, 2008 | Resubmitted: May 4th, 2009 | Accepted: February 26th, 2009 | Published: June 14th, 2010 ]

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6.2009, 10


Considering Stage Direction as Building Informed Virtual Environments

VRIC 2008 Special Issue

Alain Bonardi and Francis Rousseaux

This article begins with some recent considerations about real-time music, inspired by the latest contribution of French composer Philippe Manoury. Then, through the case study of the scenic performance La Traversée de la nuit, we analyse some perspectives for designing an Informed Virtual Environment dedicated to live show artistic domain.

[Submitted: July 22nd, 2008 | In Peer-Review: August 13th, 2008 | Resubmitted: July 1st, 2009 | Accepted: April 20th, 2009 | Published: July 20th, 2010 ]

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