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Kosmos
Astronomia Astrofizyka
Inne

Kultura
Sztuka dawna i współczesna, muzea i kolekcje

Metoda
Metodologia nauk, Matematyka, Filozofia, Miary i wagi, Pomiary

Materia
Substancje, reakcje, energia
Fizyka, chemia i inżynieria materiałowa

Człowiek
Antropologia kulturowa Socjologia Psychologia Zdrowie i medycyna

Wizje
Przewidywania Kosmologia Religie Ideologia Polityka

Ziemia
Geologia, geofizyka, geochemia, środowisko przyrodnicze

Życie
Biologia, biologia molekularna i genetyka

Cyberprzestrzeń
Technologia cyberprzestrzeni, cyberkultura, media i komunikacja

Działalność
Wiadomości | Gospodarka, biznes, zarządzanie, ekonomia

Technologie
Budownictwo, energetyka, transport, wytwarzanie, technologie informacyjne

Journal of Virtual Reality and Broadcasting (jvrb)

Journal of Virtual Reality and Broadcasting, 11(2014), no. 4.: While navigation systems for cars are in widespread use, only recently, indoor navigation systems based on smartphone apps became technically feasible. Hence tools in order to plan and evaluate particular designs of information provision are needed. Since tests in real infrastructures are costly and environmental conditions cannot be held constant, one must resort to virtual infrastructures. This paper presents the development of an environment for the support of the design of indoor navigation systems whose center piece consists in a hands-free navigation method using the Microsoft Kinect in the four-sided Definitely Affordable Virtual Environment (DAVE). Navigation controls using the user's gestures and postures as the input to the controls are designed and implemented. The installation of expensive and bulky hardware like treadmills is avoided while still giving the user a good impression of the distance she has traveled in virtual space. An advantage in comparison to approaches using a head mounted display is that the DAVE allows the users to interact with their smartphone. Thus the effects of different indoor navigation systems can be evaluated already in the planning phase using the resulting system

http://www.jvrb.org/past-issues/11.2014/3881 2014/09/05 - 19:28

Journal of Virtual Reality and Broadcasting, 11(2014), no. 2.: This paper reports on a Virtual Reality theater experiment named Il était Xn fois, conducted by artists and computer scientists working in cognitive science. It offered the opportunity for knowledge and ideas exchange between these groups, highlighting the benefits of collaboration of this kind. Section 1 explains the link between enaction in cognitive science and virtual reality, and specifically the need to develop an autonomous entity which enhances presence in an artificial world. Section 2 argues that enactive artificial intelligence is able to produce such autonomy. This was demonstrated by the theatrical experiment, "Il était Xn fois" (in English: Once upon Xn time), explained in section 3. Its first public performance was in 2009, by the company Dérézo. The last section offers the view that enaction can form a common ground between the artistic and computer science areas.

http://www.jvrb.org/past-issues/11.2014/3861 2014/02/27 - 18:18

Journal of Virtual Reality and Broadcasting, 11(2014), no. 2.: This paper reports on a Virtual Reality theater experiment named Il était Xn fois, conducted by artists and computer scientists working in cognitive science. It offered the opportunity for knowledge and ideas exchange between these groups, highlighting the benefits of collaboration of this kind. Section 1 explains the link between enaction in cognitive science and virtual reality, and specifically the need to develop an autonomous entity which enhances presence in an artificial world. Section 2 argues that enactive artificial intelligence is able to produce such autonomy. This was demonstrated by the theatrical experiment, "Il était Xn fois" (in English: Once upon Xn time), explained in section 3. Its first public performance was in 2009, by the company Dérézo. The last section offers the view that enaction can form a common ground between the artistic and computer science areas.

http://www.jvrb.org/past-issues/11.2014/3861 2014/02/27 - 18:18

Journal of Virtual Reality and Broadcastings, 11(2014), no. 1.: Imitation learning is a promising approach for generating life-like behaviors of virtual humans and humanoid robots. So far, however, imitation learning has been mostly restricted to single agent settings where observed motions are adapted to new environment conditions but not to the dynamic behavior of interaction partners. In this paper, we introduce a new imitation learning approach that is based on the simultaneous motion capture of two human interaction partners. From the observed interactions, low-dimensional motion models are extracted and a mapping between these motion models is learned. This interaction model allows the real-time generation of agent behaviors that are responsive to the body movements of an interaction partner. The interaction model can be applied both to the animation of virtual characters as well as to the behavior generation for humanoid robots.

http://www.jvrb.org/past-issues/11.2014/3856 2014/01/31 - 19:16

JVRB - Journal of Virtual Reality and Broadcasting, 10(2013), no. 7.: When depicting both virtual and physical worlds, the viewer's impression of presence in these worlds
is strongly linked to camera motion. Plausible and artist-controlled camera movement can substantially
increase scene immersion. While physical camera motion exhibits subtle details of position, rotation,
and acceleration, these details are often missing for virtual camera motion. In this work, we analyze camera movement using signal theory. Our system allows us to stylize a smooth user-defined virtual base camera motion
by enriching it with plausible details. A key component of our system is a database of videos filmed by physical
cameras. These videos are analyzed with a camera-motion estimation algorithm (structure-from-motion) and labeled
manually with a specific style. By considering spectral properties of location, orientation and acceleration, our
solution learns camera motion details. Consequently, an arbitrary virtual base motion, defined in any conventional
animation package, can be automatically modified according to a user-selected style. In an animation package
the camera motion base path is typically defined by the user via function curves. Another possibility is to obtain
the camera path by using a mixed reality camera in motion capturing studio. As shown in our experiments, the
resulting shots are still fully artist-controlled, but appear richer and more physically plausible.

http://www.jvrb.org/past-issues/10.2013/3833 2014/01/22 - 22:28

JVRB - Journal of Virtual Reality and Broadcasting, 10(2013), no. 4.: The characteristics of moving sound sources have
strong implications on the listener's distance perception
and the estimation of velocity. Modifications of the typical
sound emissions as they are currently occurring due to the
tendency towards electromobility have an impact on the
pedestrian's safety in road traffic. Thus, investigations of
the relevant cues for velocity and distance perception of
moving sound sources are not only of interest for
the psychoacoustic community, but also for several
applications, like e.g. virtual reality, noise pollution and
safety aspects of road traffic.
This article describes a series of psychoacoustic
experiments in this field. Dichotic and diotic stimuli
of a set of real-life recordings taken from a passing passenger car and a motorcycle were presented to
test subjects who in turn were asked to determine
the velocity of the object and its minimal distance
from the listener. The results of these psychoacoustic
experiments show that the estimated velocity is strongly
linked to the object's distance. Furthermore, it could be
shown that binaural cues contribute significantly to the
perception of velocity. In a further experiment, it was
shown that - independently of the type of the vehicle
- the main parameter for distance determination is
the maximum sound pressure level at the listener's
position.
The article suggests a system architecture for the adequate
consideration of moving sound sources in virtual auditory
environments. Virtual environments can thus be used to
investigate the influence of new vehicle powertrain
concepts and the related sound emissions of these vehicles
on the pedestrians' ability to estimate the distance and
velocity of moving objects.

http://www.jvrb.org/past-issues/10.2013/3800 2014/01/15 - 12:18

JVRB - Journal of Virtual Reality and Broadcasting, 10(2013), no. 3.: This paper introduces a database of freely available stereo-3D content designed to facilitate research in stereo post-production. It describes the structure and content of the database and provides some details about how the material was gathered. The database includes examples of many of the scenarios characteristic to broadcast footage. Material was gathered at different locations including a studio with controlled lighting and both indoor and outdoor on-location sites with more restricted lighting control. The database also includes video sequences with accompanying 3D audio data recorded in an Ambisonics format. An intended consequence of gathering the material is that the database contains examples of degradations that would be commonly present in real-world scenarios. This paper describes one such artefact caused by uneven exposure in the stereo views, causing saturation in the over-exposed view. An algorithm for the restoration of this artefact is proposed in order to highlight the usefuiness of the database.

http://www.jvrb.org/past-issues/10.2013/3780 2014/01/15 - 12:18

JVRB - Journal of Virtual Reality and Broadcasting, 10(2013), no. 2.: Exposure Fusion and other HDR techniques generate well-exposed images from a bracketed image sequence while reproducing a large dynamic range that far exceeds the dynamic range of a single exposure. Common to all these techniques is the problem that the smallest movements in the captured images generate artefacts (ghosting) that dramatically affect the quality of the final images. This limits the use of HDR and Exposure Fusion techniques because common scenes of interest are usually dynamic. We present a method that adapts Exposure Fusion, as well as standard HDR techniques, to allow for dynamic scene without introducing artefacts. Our method detects clusters of moving pixels within a bracketed exposure sequence with simple binary operations. We show that the proposed technique is able to deal with a large amount of movement in the scene and different movement configurations. The result is a ghost-free and highly detailed exposure fused image at a low computational cost.

http://www.jvrb.org/past-issues/10.2013/3650 2014/01/07 - 05:58

JVRB - Journal of Virtual Reality and Broadcasting, 10(2013), no. 6.: Non-verbal communication (NVC) is considered to represent more than 90 percent of everyday communication. In virtual world, this important aspect of interaction between virtual humans (VH) is strongly neglected. This paper presents a user-test study to demonstrate the impact of automatically generated graphics-based NVC expression on the dialog quality: first, we wanted to compare impassive and emotion facial expression simulation for impact on the chatting. Second, we wanted to see whether people like chatting within a 3D graphical environment. Our model only proposes facial expressions and head movements induced from spontaneous chatting between VHs. Only subtle facial expressions are being used as nonverbal cues - i.e. related to the emotional model. Motion capture animations related to hand gestures, such as cleaning glasses, were
randomly used to make the virtual human lively. After briefly introducing the technical architecture of the 3D-chatting system, we focus on two aspects of chatting through VHs. First, what is the influence of facial expressions that are induced from text dialog? For this purpose, we exploited an emotion engine extracting an emotional content from a text and depicting it into a virtual character developed previously [GAS11]. Second, as our goal was not addressing automatic generation of text, we compared the impact of nonverbal cues in conversation with a chatbot or with a human operator with a wizard of oz approach. Among main results, the within group study -involving 40 subjects- suggests that subtle facial expressions impact significantly not only on the quality of experience but also on dialog understanding.

http://www.jvrb.org/past-issues/10.2013/3823 2013/12/21 - 12:30

JVRB - Journal of Virtual Reality and Broadcasting, 10(2013), no. 5.: While depth of field is an important cinematographic means, its use in real-time computer graphics is still limited by the computational costs that are necessary to achieve a sufficient image quality. Specifically, color bleeding artifacts between objects at different depths are most effectively avoided by a decomposition into sub-images and the independent blurring of each sub-image. This decomposition, however, can result in rendering artifacts at silhouettes of objects. We propose a new blur filter that increases the opacity of all pixels to avoid these artifacts at the cost of physically less accurate but still plausible rendering results. The proposed filter is named "opaque image blur" and is based on a glow
filter that is applied to the alpha channel. We present a highly efficient GPU-based pyramid algorithm that implements this filter for depth-of-field rendering. Moreover, we demonstrate that the opaque image blur can also be used to add motion blur effects to images in real time.

http://www.jvrb.org/past-issues/10.2013/3819 2013/12/06 - 00:00

JVRB - Journal of Virtual Reality and Broadcasting, 10(2013), no. 1.: Generating and visualizing large areas of vegetation that look natural makes terrain surfaces much more realistic. However, this is a challenging field in computer graphics, because ecological systems are complex and visually appealing plant models are geometrically detailed. This work presents Silva (System for the Instantiation of Large Vegetated Areas), a system to generate and visualize large vegetated areas based on the ecological surrounding. Silva generates vegetation on Wang-tiles with associated reusable distributions enabling multi-level instantiation.
This paper presents a method to generate Poisson Disc Distributions (PDDs) with variable radii on Wang-tile sets (without a global optimization) that is able to generate seamless tilings. Because Silva has a freely configurable generation pipeline and can consider plant neighborhoods it is able to incorporate arbitrary abiotic and biotic components during generation. Based on multi-level
instancing and nested kd-trees, the distributions on the Wang-tiles allow their acceleration structures to be reused during visualization. This enables Silva to visualize large vegetated areas of several hundred square kilometers with low render times and a small memory footprint.

http://www.jvrb.org/past-issues/10.2013/3632 2013/07/31 - 13:04

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 5.: In this paper, we present a set of tools developed during the creation of a platform that allows the automatic generation of virtual views in a live soccer game production. Observing the scene through a multi-camera system, a 3D approximation of the players is computed and used for the synthesis of virtual views. The system is suitable both for static scenes, to create bullet time effects, and for video applications, where the virtual camera moves as the game plays.

http://www.jvrb.org/past-issues/9.2012/3513 2013/07/31 - 13:04

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 3.: We address the problem of representing captured images in the continuous mathematical space more usually associated with certain forms of drawn ('vector') images. Such an image is resolution-independent so can be used as a master for varying resolution-specific formats. We briefly describe the main features of a vectorising codec for photographic images, whose significance is that drawing programs can access images and image components as first-class vector objects. This paper focuses on the problem of rendering from the isochromic contour form of a vectorised image and demonstrates a new fill algorithm which could also be used in drawing generally. The fill method is described in terms of level set diffusion equations for clarity. Finally we show that image warping is both simplified and enhanced in the vector form and that we can demonstrate real histogram equalisation with genuinely rectangular histograms straightforwardly.

http://www.jvrb.org/past-issues/9.2012/3271 2013/07/31 - 13:04

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 7.: We present an improvement of TSTM, a recently proposed tone mapping operator for High Dynamic Range (HDR) images, based on a multi-modal analysis. One of the key features of TSTM is a suitable implementation of the Naka-Rushton equation that mimics the visual adaptation performed by the human visual system coherently with Weber-Fechner's law of contrast perception. In the present paper we use the Gaussian Mixture Model (GMM) in order to detect the modes of the log-scale luminance histogram of a given HDR image and then we use the information provided by GMM to properly devise a Naka-Rushton equation for each mode. Finally, we properly select the parameters in order to merge those equations into a continuous function. Tests and comparisons to show how this new method is capable of improving the performances of TSTM are provided and commented, as well as comparisons with state of the art methods.

http://www.jvrb.org/past-issues/9.2012/3514 2013/07/31 - 13:04

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 4.: When stereo images are captured under less than ideal conditions, there may be inconsistencies between the two images in brightness, contrast, blurring, etc. When stereo matching is performed between the images, these variations can greatly reduce the quality of the resulting depth map. In this paper we propose a method for correcting sharpness variations in stereo image pairs which is performed as a pre-processing step to stereo matching. Our method is based on scaling the 2D discrete cosine transform (DCT) coefficients of both images so that the two images have the same amount of energy in each of a set of frequency bands. Experiments show that applying the proposed correction method can greatly improve the disparity map quality when one image in a stereo pair is more blurred than the other.

http://www.jvrb.org/past-issues/9.2012/3290 2013/07/31 - 13:04

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 9.: Virtual environments (VE) are gaining in popularity and are increasingly used for teamwork training purposes, e.g., for medical teams. One shortcoming of modern VEs is that nonverbal communication channels, essential for teamwork, are not supported well. We address this issue by using an inexpensive webcam to track the user's head. This tracking information is used to control the head movement of the user's avatar, thereby conveying head gestures and adding a nonverbal communication channel. We conducted a user study investigating the influence of head tracking based avatar control on the perceived realism of the VE and on the performance of a surgical teamwork training scenario. Our results show that head tracking positively influences the perceived realism of the VE and the communication, but has no major influence on the training outcome.

http://www.jvrb.org/past-issues/9.2012/3560 2013/07/31 - 13:04

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 8.: We present an algorithm for estimating dense image correspondences. Our versatile approach lends itself to various tasks typical for video post-processing, including image morphing, optical flow estimation, stereo rectification, disparity/depth reconstruction, and baseline adjustment. We incorporate recent advances in feature matching, energy minimization, stereo vision, and data clustering into our approach. At the core of our correspondence estimation we use Efficient Belief Propagation for energy minimization.

While state-of-the-art algorithms only work on thumbnail-sized images, our novel feature downsampling scheme in combination with a simple, yet efficient data term compression, can cope with high-resolution data. The incorporation of SIFT (Scale-Invariant Feature Transform) features into data term computation further resolves matching ambiguities, making long-range correspondence estimation possible. We detect occluded areas by evaluating the correspondence symmetry, we further apply Geodesic matting to automatically determine plausible values in these regions.

http://www.jvrb.org/past-issues/9.2012/3554 2013/07/31 - 13:04

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 6.: We present a high performance-yet low cost-system for multi-view rendering in virtual reality (VR) applications. In contrast to complex CAVE installations, which are typically driven by one render client per view, we arrange eight displays in an octagon around the viewer to provide a full 360° projection, and we drive these eight displays by a single PC equipped with multiple graphics units (GPUs). In this paper we describe the hardware and software setup, as well as the necessary low-level and high-level optimizations to optimally exploit the parallelism of this multi-GPU multi-view VR system.

http://www.jvrb.org/past-issues/9.2012/3511 2013/07/31 - 13:04

JVRB - Journal of Virtual Reality and Broadcasting, 9.2012, no. 1.: In this paper we present XSAMPL3D, a novel language for the high-level representation of actions performed on objects by (virtual) humans. XSAMPL3D was designed to serve as action representation language in an imitation-based approach to character animation: First, a human demonstrates a sequence of object manipulations in an immersive Virtual Reality (VR) environment. From this demonstration, an XSAMPL3D description is automatically derived that represents the actions in terms of high-level action types and involved objects. The XSAMPL3D action description can then be used for the synthesis of animations where virtual humans of different body sizes and proportions reproduce the demonstrated action. Actions are encoded in a compact and human-readable XML-format. Thus, XSAMPL3D describtions are also amenable to manual authoring, e.g. for rapid prototyping of animations when no immersive VR environment is at the animator's disposal. However, when XSAMPL3D descriptions are derived from VR interactions, they can accomodate many details of the demonstrated action, such as motion trajectiories,hand shapes and other hand-object relations during grasping. Such detail would be hard to specify with manual motion authoring techniques only. Through the inclusion of language features that allow the representation of all relevant aspects of demonstrated object manipulations, XSAMPL3D is a suitable action representation language for the imitation-based approach to character animation.

http://www.jvrb.org/past-issues/9.2012/3262 2013/07/31 - 13:04

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 2.: We present an image-based method for relighting a scene by analytically fitting cosine lobes to the reflectance function at each pixel, based on gradient illumination photographs. Realistic relighting results for many materials are obtained using a single per-pixel cosine lobe obtained from just two color photographs: one under uniform white illumination and the other under colored gradient illumination. For materials with wavelength-dependent scattering, a better fit can be obtained using independent cosine lobes for the red, green, and blue channels, obtained from three achromatic gradient illumination conditions instead of the colored
gradient condition. We explore two cosine lobe reflectance functions, both of which allow an analytic fit to the
gradient conditions. One is non-zero over half the sphere of lighting directions, which works well for diffuse and specular materials, but fails for materials with broader scattering such as fur. The other is non-zero everywhere, which works well for broadly scattering materials and still produces visually plausible results for diffuse and specular materials. We also perform an approximate diffuse/specular separation of the reflectance, and estimate scene geometry from the recovered photometric normals to produce hard shadows cast by the geometry, while still reconstructing the input photographs exactly.

http://www.jvrb.org/past-issues/9.2012/3264 2013/07/31 - 13:04

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 5.: In this paper, we present a set of tools developed during the creation of a platform that allows the automatic generation of virtual views in a live soccer game production. Observing the scene through a multi-camera system, a 3D approximation of the players is computed and used for the synthesis of virtual views. The system is suitable both for static scenes, to create bullet time effects, and for video applications, where the virtual camera moves as the game plays.

http://www.jvrb.org/9.2012/3513 2013/07/24 - 07:50

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 3.: We address the problem of representing captured images in the continuous mathematical space more usually associated with certain forms of drawn ('vector') images. Such an image is resolution-independent so can be used as a master for varying resolution-specific formats. We briefly describe the main features of a vectorising codec for photographic images, whose significance is that drawing programs can access images and image components as first-class vector objects. This paper focuses on the problem of rendering from the isochromic contour form of a vectorised image and demonstrates a new fill algorithm which could also be used in drawing generally. The fill method is described in terms of level set diffusion equations for clarity. Finally we show that image warping is both simplified and enhanced in the vector form and that we can demonstrate real histogram equalisation with genuinely rectangular histograms straightforwardly.

http://www.jvrb.org/9.2012/3271 2013/06/29 - 12:49

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 7.: We present an improvement of TSTM, a recently proposed tone mapping operator for High Dynamic Range (HDR) images, based on a multi-modal analysis. One of the key features of TSTM is a suitable implementation of the Naka-Rushton equation that mimics the visual adaptation performed by the human visual system coherently with Weber-Fechner's law of contrast perception. In the present paper we use the Gaussian Mixture Model (GMM) in order to detect the modes of the log-scale luminance histogram of a given HDR image and then we use the information provided by GMM to properly devise a Naka-Rushton equation for each mode. Finally, we properly select the parameters in order to merge those equations into a continuous function. Tests and comparisons to show how this new method is capable of improving the performances of TSTM are provided and commented, as well as comparisons with state of the art methods.

http://www.jvrb.org/9.2012/3514 2013/06/28 - 09:44

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 4.: When stereo images are captured under less than ideal conditions, there may be inconsistencies between the two images in brightness, contrast, blurring, etc. When stereo matching is performed between the images, these variations can greatly reduce the quality of the resulting depth map. In this paper we propose a method for correcting sharpness variations in stereo image pairs which is performed as a pre-processing step to stereo matching. Our method is based on scaling the 2D discrete cosine transform (DCT) coefficients of both images so that the two images have the same amount of energy in each of a set of frequency bands. Experiments show that applying the proposed correction method can greatly improve the disparity map quality when one image in a stereo pair is more blurred than the other.

http://www.jvrb.org/9.2012/3290 2013/04/25 - 18:56

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 4.: When stereo images are captured under less than ideal conditions, there may be inconsistencies between the two images in brightness, contrast, blurring, etc. When stereo matching is performed between the images, these variations can greatly reduce the quality of the resulting depth map. In this paper we propose a method for correcting sharpness variations in stereo image pairs which is performed as a pre-processing step to stereo matching. Our method is based on scaling the 2D discrete cosine transform (DCT) coefficients of both images so that the two images have the same amount of energy in each of a set of frequency bands. Experiments show that applying the proposed correction method can greatly improve the disparity map quality when one image in a stereo pair is more blurred than the other.

http://www.jvrb.org/9.2012/3290 2013/04/25 - 18:56

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 9.: Virtual environments (VE) are gaining in popularity and are increasingly used for teamwork training purposes, e.g., for medical teams. One shortcoming of modern VEs is that nonverbal communication channels, essential for teamwork, are not supported well. We address this issue by using an inexpensive webcam to track the user's head. This tracking information is used to control the head movement of the user's avatar, thereby conveying head gestures and adding a nonverbal communication channel. We conducted a user study investigating the influence of head tracking based avatar control on the perceived realism of the VE and on the performance of a surgical teamwork training scenario. Our results show that head tracking positively influences the perceived realism of the VE and the communication, but has no major influence on the training outcome.

http://www.jvrb.org/9.2012/3560 2013/02/06 - 16:33

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 8.: We present an algorithm for estimating dense image correspondences. Our versatile approach lends itself to various tasks typical for video post-processing, including image morphing, optical flow estimation, stereo rectification, disparity/depth reconstruction, and baseline adjustment. We incorporate recent advances in feature matching, energy minimization, stereo vision, and data clustering into our approach. At the core of our correspondence estimation we use Efficient Belief Propagation for energy minimization.

While state-of-the-art algorithms only work on thumbnail-sized images, our novel feature downsampling scheme in combination with a simple, yet efficient data term compression, can cope with high-resolution data. The incorporation of SIFT (Scale-Invariant Feature Transform) features into data term computation further resolves matching ambiguities, making long-range correspondence estimation possible. We detect occluded areas by evaluating the correspondence symmetry, we further apply Geodesic matting to automatically determine plausible values in these regions.

http://www.jvrb.org/9.2012/3554 2013/01/23 - 02:44

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 6.: We present a high performance-yet low cost-system for multi-view rendering in virtual reality (VR) applications. In contrast to complex CAVE installations, which are typically driven by one render client per view, we arrange eight displays in an octagon around the viewer to provide a full 360° projection, and we drive these eight displays by a single PC equipped with multiple graphics units (GPUs). In this paper we describe the hardware and software setup, as well as the necessary low-level and high-level optimizations to optimally exploit the parallelism of this multi-GPU multi-view VR system.

http://www.jvrb.org/9.2012/3511 2012/12/05 - 20:15

JVRB - Journal of Virtual Reality and Broadcasting, 9.2012, no. 1.: In this paper we present XSAMPL3D, a novel language for the high-level representation of actions performed on objects by (virtual) humans. XSAMPL3D was designed to serve as action representation language in an imitation-based approach to character animation: First, a human demonstrates a sequence of object manipulations in an immersive Virtual Reality (VR) environment. From this demonstration, an XSAMPL3D description is automatically derived that represents the actions in terms of high-level action types and involved objects. The XSAMPL3D action description can then be used for the synthesis of animations where virtual humans of different body sizes and proportions reproduce the demonstrated action. Actions are encoded in a compact and human-readable XML-format. Thus, XSAMPL3D describtions are also amenable to manual authoring, e.g. for rapid prototyping of animations when no immersive VR environment is at the animator's disposal. However, when XSAMPL3D descriptions are derived from VR interactions, they can accomodate many details of the demonstrated action, such as motion trajectiories,hand shapes and other hand-object relations during grasping. Such detail would be hard to specify with manual motion authoring techniques only. Through the inclusion of language features that allow the representation of all relevant aspects of demonstrated object manipulations, XSAMPL3D is a suitable action representation language for the imitation-based approach to character animation.

http://www.jvrb.org/9.2012/3262 2012/04/21 - 18:57

JVRB - Journal of Virtual Reality and Broadcasting, 9(2012), no. 2.: We present an image-based method for relighting a scene by analytically fitting cosine lobes to the reflectance function at each pixel, based on gradient illumination photographs. Realistic relighting results for many materials are obtained using a single per-pixel cosine lobe obtained from just two color photographs: one under uniform white illumination and the other under colored gradient illumination. For materials with wavelength-dependent scattering, a better fit can be obtained using independent cosine lobes for the red, green, and blue channels, obtained from three achromatic gradient illumination conditions instead of the colored
gradient condition. We explore two cosine lobe reflectance functions, both of which allow an analytic fit to the
gradient conditions. One is non-zero over half the sphere of lighting directions, which works well for diffuse and specular materials, but fails for materials with broader scattering such as fur. The other is non-zero everywhere, which works well for broadly scattering materials and still produces visually plausible results for diffuse and specular materials. We also perform an approximate diffuse/specular separation of the reflectance, and estimate scene geometry from the recovered photometric normals to produce hard shadows cast by the geometry, while still reconstructing the input photographs exactly.

http://www.jvrb.org/9.2012/3264 2012/04/21 - 18:57

JVRB - Journal of Virtual Reality and Broadcasting, 8(2011), no. 3.: The article presents the design process of intelligent
virtual human patients that are used for the enhancement
of clinical skills. The description covers the development
from conceptualization and character creation to technical
components and the application in clinical research and
training. The aim is to create believable social interactions
with virtual agents that help the clinician to develop skills
in symptom and ability assessment, diagnosis, interview
techniques and interpersonal communication. The virtual
patient fulfills the requirements of a standardized patient
producing consistent, reliable and valid interactions in
portraying symptoms and behaviour related to a specific
clinical condition.

http://www.jvrb.org/past-issues/8.2011/2902 2012/04/21 - 18:57

JVRB - Journal of Virtual Reality and Broadcasting, 8(2011), no. 2.: Visual fixation is employed by humans and some animals
to keep a specific 3D location at the center of
the visual gaze. Inspired by this phenomenon in nature,
this paper explores the idea to transfer this mechanism
to the context of video stabilization for a handheld
video camera. A novel approach is presented
that stabilizes a video by fixating on automatically
extracted 3D target points. This approach is different
from existing automatic solutions that stabilize
the video by smoothing. To determine the 3D target
points, the recorded scene is analyzed with a stateof-
the-art structure-from-motion algorithm, which estimates
camera motion and reconstructs a 3D point
cloud of the static scene objects. Special algorithms
are presented that search either virtual or real 3D target
points, which back-project close to the center of the
image for as long a period of time as possible. The stabilization algorithm then transforms the original images
of the sequence so that these 3D target points are
kept exactly in the center of the image, which, in case
of real 3D target points, produces a perfectly stable result
at the image center. Furthermore, different methods
of additional user interaction are investigated. It is
shown that the stabilization process can easily be controlled
and that it can be combined with state-of-theart
tracking techniques in order to obtain a powerful
image stabilization tool. The approach is evaluated on
a variety of videos taken with a hand-held camera in
natural scenes.

http://www.jvrb.org/past-issues/8.2011/2822 2012/04/21 - 18:57

JVRB - Journal of Virtual Reality and Broadcasting, 8(2011), no. 1.: In this paper we present a hybrid method to track human
motions in real-time. With simplified marker
sets and monocular video input, the strength of both
marker-based and marker-free motion capturing are
utilized: A cumbersome marker calibration is avoided
while the robustness of the marker-free tracking is enhanced
by referencing the tracked marker positions.
An improved inverse kinematics solver is employed
for real-time pose estimation. A computer-visionbased
approach is applied to refine the pose estimation
and reduce the ambiguity of the inverse kinematics solutions.
We use this hybrid method to capture typical
table tennis upper body movements in a real-time virtual
reality application.

http://www.jvrb.org/past-issues/8.2011/2819 2012/04/21 - 18:57

JVRB - Journal of Virtual Reality and Broadcasting, 7(2010), no. 11.: This article describes a series of experiments which
were carried out to measure the sense of presence in
auditory virtual environments.
Within the study a comparison of self-created signals
to signals created by the surrounding environment is
drawn. Furthermore, it is investigated if the room characteristics
of the simulated environment have consequences
on the perception of presence during vocalization
or when listening to speech. Finally the experiments
give information about the influence of background
signals on the sense of presence.
In the experiments subjects rated the degree of perceived
presence in an auditory virtual environment on
a perceptual scale. It is described which parameters
have the most influence on the perception of presence and which ones are of minor influence. The results
show that on the one hand an external speaker
has more influence on the sense of presence than an
adequate presentation of one’s own voice. On the
other hand both room reflections and adequately presented
background signals significantly increase the
perceived presence in the virtual environment.

http://www.jvrb.org/past-issues/7.2010/2679 2012/04/21 - 18:57

JVRB - Journal of Virtual Reality and Broadcasting, 7(2010), no. 10.: Given arbitrary pictures, we explore the possibility
of using new techniques from computer vision and
artificial intelligence to create customized visual games
on-the-fly. This includes coloring books, link-the-dot and
spot-the-difference popular games. The feasibility of
these systems is discussed and we describe prototype
implementation that work well in practice in an automatic
or semi-automatic way.

http://www.jvrb.org/past-issues/7.2010/2670 2012/04/21 - 18:57

JVRB - Journal of Virtual Reality and Broadcasting, 7(2010), no. 9.: This contribution discusses the effects of camera aperture
correction in broadcast video on colour-based keying. The
aperture correction is used to ’sharpen’ an image and is one
element that distinguishes the ’TV-look’ from ’film-look’. ’If a
very high level of sharpening is applied, as is the case in many
TV productions then this significantly shifts the colours around
object boundaries with hight contrast. This paper discusses
these effects and their impact on keying and describes a simple
low-pass filter to compensate for them. Tests with colour-based
segmentation algorithms show that the proposed compensation
is an effective way of decreasing the keying artefacts on object
boundaries.

http://www.jvrb.org/past-issues/7.2010/2669 2012/04/21 - 18:57

JVRB - Journal of Virtual Reality and Broadcasting, 7(2010), no. 8.: Recently, stable markerless 6 DOF video based handtracking
devices became available. These devices simultaneously
track the positions and orientations of
both user hands in different postures with at least 25
frames per second. Such hand-tracking allows for using
the human hands as natural input devices. However,
the absence of physical buttons for performing
click actions and state changes poses severe challenges
in designing an efficient and easy to use 3D interface
on top of such a device. In particular, for coupling and
decoupling a virtual object’s movements to the user’s
hand (i.e. grabbing and releasing) a solution has to
be found. In this paper, we introduce a novel technique
for efficient two-handed grabbing and releasing
objects and intuitively manipulating them in the virtual
space. This technique is integrated in a novel
3D interface for virtual manipulations. A user experiment
shows the superior applicability of this new technique.
Last but not least, we describe how this technique
can be exploited in practice to improve interaction
by integrating it with RTT DeltaGen, a professional CAD/CAS visualization and editing tool.

http://www.jvrb.org/past-issues/7.2010/2668 2012/04/21 - 18:57

JVRB - Journal of Virtual Reality and Broadcasting, 7(2010), no. 7.: wo methods for registering laser-scans of human heads and transforming them to a new semantically consistent topology defined by a user-provided template mesh are described. Both algorithms are stated within the Iterative Closest Point framework. The first method is based on finding landmark correspondences by iteratively registering the vicinity of a landmark with a re-weighted error function. Thin-plate spline interpolation is then used to deform the template mesh and finally the scan is resampled in the topology of the deformed template. The second algorithm employs a morphable shape model, which can be computed from a database of laser-scans using the first algorithm. It directly optimizes pose and shape of the morphable model. The use of the algorithm with PCA mixture models, where the shape is split up into regions each described by an individual subspace, is addressed. Mixture models require either blending or regularization strategies, both of which are described in detail. For both algorithms, strategies for filling in missing geometry for incomplete laser-scans are described. While an interpolation-based approach can be used to fill in small or smooth regions, the model-driven algorithm is capable of fitting a plausible complete head mesh to arbitrarily small geometry, which is known as "shape completion". The importance of regularization in the case of extreme shape completion is shown.

http://www.jvrb.org/past-issues/7.2010/2662 2012/04/21 - 18:57

JVRB - Journal of Virtual Reality and Broadcasting, 7(2010), no. 6.: We present a new approach to diffuse reflectance estimation
for dynamic scenes.
Non-parametric image statistics are used to transfer
reflectance properties from a static example set to a
dynamic image sequence.
The approach allows diffuse reflectance estimation
for surface materials with inhomogeneous appearance,
such as those which commonly occur with patterned or
textured clothing. Material editing is also possible by
transferring edited reflectance properties.
Material reflectance properties are initially estimated
from static images of the subject under multiple
directional illuminations using photometric stereo.
The estimated reflectance together with the corresponding
image under uniform ambient illumination
form a prior set of reference material observations.
Material reflectance properties are then estimated
for video sequences of a moving person captured under
uniform ambient illumination by matching the
observed local image statistics to the reference observations.
Results demonstrate that the transfer of
reflectance properties enables estimation of the dynamic
surface normals and subsequent relighting combined
with material editing. This approach overcomes
limitations of previous work on material transfer
and relighting of dynamic scenes which was limited
to surfaces with regions of homogeneous reflectance.
We evaluate our approach for relighting
3D model sequences reconstructed from multiple
view video. Comparison to previous model relighting
demonstrates improved reproduction of detailed texture
and shape dynamics.

http://www.jvrb.org/past-issues/7.2010/2653 2012/04/21 - 18:57

JVRB - Journal of Virtual Reality and Broadcasting, 7(2010), no. 5.: This paper presents two studies pertaining to the use
of virtual characters applied in clinical forensic rehabilitation
of sex offenders. The first study is about the
validation of the perceived age of virtual characters designed
to simulate primary and secondary sexual character
of typical adult and child individuals. The second
study puts to use these virtual characters in comparing
a group of sex offenders and a group of non
deviant individuals on their sexual arousal responses
as recorded in virtual immersion. Finally, two clinical
vignettes illustrating the use of made-to-measure virtual
characters to more closely fit sexual preferences
are presented in Discussion.

http://www.jvrb.org/past-issues/7.2010/2646 2012/04/21 - 18:57