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VRST Tables of Contents: 979899000102030405060708091012131415

Proceedings of the 2010 ACM Symposium on Virtual Reality Software and Technology

Fullname:VRST'10 ACM Symposium on Virtual Reality Software and Technology
Editors:George Baciu; Rynson Lau; Ming Lin; Taku Komura; Qunsheng Peng
Location:Hong Kong
Dates:2010-Nov-22 to 2010-Nov-24
Publisher:ACM
Standard No:ISBN: 1-4503-0441-9, 978-1-4503-0441-2; ACM DL: Table of Contents hcibib: VRST10
Papers:43
Pages:234
Links:Conference Home Page
  1. Augmented reality
  2. Modeling and simulations
  3. Poster session 1
  4. Interactions
  5. Rendering and visualization
  6. Poster session 2
  7. Human factors and collaborative virtual environments (part 1)
  8. Human factors and collaborative virtual environments (part 2)

Augmented reality

Augmentation techniques for efficient exploration in head-mounted display environments BIBAFull-Text 11-18
  Benjamin Bolte; Gerd Bruder; Frank Steinicke; Klaus Hinrichs; Markus Lappe
Physical characteristics and constraints of today's head-mounted displays (HMDs) often impair interaction in immersive virtual environments (VEs). For instance, due to the limited field of view (FOV) subtended by the display units in front of the user's eyes more effort is required to explore a VE by head rotations than for exploration in the real world.
   In this paper we propose a combination of two augmentation techniques that have the potential to make exploration of VEs more efficient: (1) augmenting the geometric FOV (GFOV) used for rendering the VE, and (2) amplifying head rotations while the user changes her head orientation. In order to identify how much manipulation can be applied without users noticing, we conducted two psychophysical experiments in which we analyzed subjects' ability to discriminate between virtual and real head pitch and roll rotations while three different geometric FOVs were used. Our results show that the combination of both techniques has great potential to support efficient exploration of VEs. We found that virtual pitch and roll rotations can be amplified by 30% and 44% respectively, when the GFOV matches the subject's estimation of the most natural FOV. This leads to a possible reduction of the user's effort required to explore the VE using a combination of both techniques by approximately 25%.
Making first steps in VR: monitoring user progress in virtual travel BIBAFull-Text 19-26
  Andrei Sherstyuk; Dale Vincent; Kin Lik Wang
We propose a novel framework for monitoring and evaluating user travel activity in Virtual Reality (VR), in real time. Using this framework, we examined how users progressed in mastering two common travel techniques: steering and target-based relocation. We identified three groups of subjects with distinctly different learning patterns, which we called advancing, neutral and regressing learners. In this paper, we explain our evaluation method in detail, describe the experimental study, discuss the results and practical applications of our findings.
Shake-your-head: revisiting walking-in-place for desktop virtual reality BIBAFull-Text 27-34
  Léo Terziman; Maud Marchal; Mathieu Emily; Franck Multon; Bruno Arnaldi; Anatole Lécuyer
The Walking-In-Place interaction technique was introduced to navigate infinitely in 3D virtual worlds by walking in place in the real world. The technique has been initially developed for users standing in immersive setups and was built upon sophisticated visual displays and tracking equipments.
   In this paper, we propose to revisit the whole pipeline of the Walking-In-Place technique to match a larger set of configurations and apply it notably to the context of desktop Virtual Reality. With our novel "Shake-Your-Head" technique, the user is left with the possibility to sit down, and to use small screens and standard input devices such as a basic webcam for tracking. The locomotion simulation can compute various motions such as turning, jumping and crawling, using as sole input the head movements of the user. We also introduce the use of additional visual feedback based on camera motions to enhance the walking sensations.
   An experiment was conducted to compare our technique with classical input devices used for navigating in desktop VR. Interestingly, the results showed that our technique could even allow faster navigations when sitting, after a short learning. Our technique was also perceived as more fun and increasing presence, and was generally more appreciated for VR navigation.
An adaptive training-free feature tracker for mobile phones BIBAFull-Text 35-42
  Jan Herling; Wolfgang Broll
While tracking technologies based on fiducial markers have dominated the development of Augmented Reality (AR) applications for almost a decade, various real-time capable approaches to markerless tracking have recently been presented. However, most existing approaches do not yet achieve sufficient frame rates for AR on mobile phones or at least require an extensive training phase in advance.
   In this paper we will present our approach on feature based tracking applying robust SURF features. The implementation is more than one magnitude faster than previous ones, allowing running even on mobile phones at highly interactive rates. In contrast to other feature based approaches on mobile phones, our implementation may immediately track features captured from a photo without any training. Further, the approach is not restricted to planar surfaces, but may use features of 3D objects.
Dynamic eye convergence for head-mounted displays BIBAFull-Text 43-46
  Andrei Sherstyuk; Andrei State
A virtual hand metaphor remains by far the most popular technique for direct object manipulation in immersive Virtual Reality (VR). The utility of the virtual hand depends on a user's ability to see it correctly in stereoscopic 3D, especially in tasks that require continuous, precise hand-eye coordination.
   We present a mechanism that dynamically converges left and right cameras on target objects in VR, mimicking the effect that naturally happens in real life. As a result, the system maintains optimal conditions for stereoscopic viewing at varying depths, in real-time. We describe the algorithm, implementation details and preliminary results from pilot tests.
A first person avatar system with haptic feedback BIBAFull-Text 47-50
  Bernhard Spanlang; Jean-Marie Normand; Elias Giannopoulos; Mel Slater
We describe a system that shows how to substitute a person's body in virtual reality by a virtual body (or avatar). The avatar is seen from a first person perspective, moves as the person moves and the system generates touch on the real person's body when the avatar is touched. Such replacement of the person's real body by a virtual body requires a wide field-of-view head-mounted display, real-time whole body tracking, and tactile feedback. We show how to achieve this with a variety of off-the-shelf hardware and software, and also custom systems for real-time avatar rendering and collision detection. We present an overview of the system and detail on some of its components. We provide examples of how such a system is being used in some of our current experimental studies of embodiment.
Image-based 3D telecopier: a system for sharing a 3D object by multiple groups of people at remote locations BIBAFull-Text 51-54
  Yoshifumi Kitamura; Tetsuya Kikukawa; Satoshi Mieda; Yotaka Kunita; Megumi Isogai; Hideaki Kimata
We propose a system that allows multiple groups of users at remote locations to naturally share a 3D image of real objects. All users can interactively observe a 3D stereoscopic image without distortion from their own viewpoints. The system basically consists of a combination of subsystems: imaging and display. The imaging subsystem generates images of the real object observed from arbitrary viewpoints based on image-based rendering technique implemented on GPU. The display system generates a 3D virtual image of the real object to be interactively observed by multiple people around the tabletop display. People at one place just put the real object on their imaging system to capture a set of its images from sparse viewpoints around it; other groups of multiple persons at remote places connected by networks observe its virtual image from arbitrary viewpoints, as if there is a copy of the real object, on their display systems. This paper describes details of the system configurations and algorithms. Then discussions are made based on experimental results.

Modeling and simulations

Robust continuous collision detection for deformable objects BIBAFull-Text 55-62
  Sai-Keung Wong; Cheng-Min Liu; George Baciu; Chiao-Chin Yeh
Continuous collision detection improves the computation of the contact information for interacting objects in dynamic virtual environments. The computation cost is relatively high in the phase of the elementary test processing. In virtual environments, such as crowds in large urban models, there is a large portion of feature pairs that do not collide but the computation is relatively of high cost. In this paper, we propose a robust approach for solving the scalability of the collision detection problem by applying four distinct phases. First, k-DOPs are used for culling non-proximal triangles. Second, the feature assignment scheme is used for minimizing the number of potentially colliding feature pairs. Third, an intrinsic filter is employed for filtering non-coplanar feature pairs. Forth, we use a direct method for computing the contact time that is more efficient than the numerical Interval Newton method. We have implemented our system and have compared its performance with the most recently developed approaches. Six benchmarks were evaluated and the complexity of the models was up to 1.5M triangles. The experimental results show that our method improves the performance for the elementary tests.
A benchmarking suite for 6-DOF real time collision response algorithms BIBAFull-Text 63-70
  Rene Weller; Mikel Sagardia; David Mainzer; Thomas Hulin; Gabriel Zachmann; Carsten Preusche
We present a benchmarking suite for rigid object collision detection and collision response schemes. The proposed benchmarking suite can evaluate both the performance as well as the quality of the collision response. The former is achieved by densely sampling the configuration space of a large number of highly detailed objects; the latter is achieved by a novel methodology that comprises a number of models for certain collision scenarios. With these models, we compare the force and torque signals both in direction and magnitude.
   Our device-independent approach allows objective predictions for physically-based simulations as well as 6-DOF haptic rendering scenarios. In the results, we show a comprehensive example application of our benchmarks comparing two quite different algorithms utilizing our proposed benchmarking suite. This proves empirically that our methodology can become a standard evaluation framework.
Automatic generation of head models and facial animations considering personal characteristics BIBAFull-Text 71-78
  Akinobu Maejima; Hiroto Yarimizu; Hiroyuki Kubo; Shigeo Morishima
We propose a new automatic head modeling system to generate individualized head models which can express person-specific facial expressions. The head modeling system consists of two core processes. The head modeling process with the proposed automatic mesh completion generates a whole head model only from facial range scan data. The key shape generation process generates key shapes for the generated head model based on physics-based facial muscle simulation with an individual muscle layout estimated from subject's facial expression videos. Facial animations considering personal characteristics can be synthesized using the individualized head model and key shapes. Experimental results show that the proposed system can generate head models where 84% of subjects can identify themselves. Therefore, we conclude that our head modeling system is effective to games and entertainment systems like a Future Cast System.
Reduced deforming filter culling for fast continuous collision detection BIBAFull-Text 79-82
  Chen Tang; Sheng Li; Guoping Wang
We propose a novel efficient deforming filter culling method for continuous collision detection (CCD) problem performed by dimension reduction in subspace. We present a fast linear filter (1D reduced filter) considering relative motion between primitives. We also provide a conservative and fast planar filter test (2D reduced filter) for self-collision feature pairs considering relative motion between vertex and edge. Filter test in subspace removes large amount of false positives and elementary tests with low cost, and improve the overall performance of collision query. We demonstrate our approach and compare it with previous alternatives in kinds of dynamic scenes. Combined with our linear and planar reduced filter, we observe a magnitude of speed improvement on elementary tests (over 2x) compared against previous ones. Our method keeps stable performance for simulations with large step time.
Physically-based animation for realistic interactions between tree branches and raindrops BIBAFull-Text 83-86
  Meng Yang; Meng-Cheng Huang; Gang Yang; En-Hua Wu
This paper proposes a novel approach to animation realistic interactions between tree branches and raindrops in a physically-based way. A new elastic model using a three-prism structures is presented to flexibly bend and twist tree branches naturally in the first time. Various distinct forms of interactions when or after raindrops hitting on tree branches can be well simulated using a new efficient technique specially designed for liquid motion on non-rigid objects with hydrophilic surfaces. Experimental results indicate that our approach can be used to simulate the interactions between tree branches and raindrops efficiently and realistically.
Can we distinguish biological motions of virtual humans?: perceptual study with captured motions of weight lifting BIBAFull-Text 87-90
  Ludovic Hoyet; Franck Multon; Anatole Lecuyer; Taku Komura
Perception of biological motions is a key issue in order to evaluate the quality and the credibility of motions of virtual humans. This paper presents a perceptual study to evaluate if human beings are able to accurately distinguish differences in natural lifting motions with various masses in virtual environments (VE), which is not the case. However, they reached very close levels of accuracy when watching to computer animations compared to videos. Still, quotes of participants suggest that the discrimination process is easier in videos of real motions which included muscles contractions, more degrees of freedom, etc. These results can be used to help animators to design efficient physically-based animations.

Poster session 1

Modeling spatially-varying reflectance based on Kernel Nyström BIBAFull-Text 91-92
  Yong Hu; Yue Qi; Fangyang Shen
We present a new method for modeling real-world surface reflectance, described with non-parametric spatially-varying bidirectional reflectance distribution functions (SVBRDF). Our method seeks to achieve high reconstruction accuracy, compactness and "editability" of representation meanwhile speeding up both the SVBRDF capturing and modeling processes. For a planar surface, we 1) design a fast capturing device to acquire reflectance samples at dense surface locations; 2) propose a Laplacian-based angular interpolation scheme for a 2D slice of BRDF at a given surface location, and then a Kernel Nyström method for SVBRDF data matrix reconstruction; 3) propose a practical algorithm to extract linear-independent basis BRDFs, and to calculate blending weights through projecting reconstructed reflectance onto these bases. Results demonstrate that our approach models real-world reflectance with both high accuracy and high visual fidelity for real-time virtual environment rendering.
Efficient deformable geometry image-maps BIBAFull-Text 93-94
  Bin Sheng; Hanqiu Sun
Multiresolution rendering of deformable models, performing fast rendering of global deformations while preserving local surface details, is usually a computation-costly and time-consuming process, because two non-trivial operators are involved. We propose a novel GPU-based adaptive rendering of deforming mesh sequence on sole-cube maps (SCM), which is a variant of geometry images built upon spherical parameterizations. We also introduce the differential coordinates to bound the local resampling error for supporting details preservation and view-dependent visualization. By precomputing the adaptive SCM texture atlas of deforming mesh sequences as well as their differential coordinates, we can map both the deformation and the level-of-details (LOD) operator to the GPU. The proposed algorithm enables us to reconstruct the deformed positions and sufficiently fine-scale approximations of deforming mesh sequences for efficient GPU processing. The GPU-friendly data structure and process allow us to render dynamically deforming 3D models with GPU parallelization, also our system improves the efficiency of the manipulations of node selection and boundary stitching, significantly alleviating the computing load on CPU.
Locating human hands for real-time pose estimation from monocular video BIBAFull-Text 95-96
  Xin Lian; Qingmin Liao
This paper presents a real-time system to detect and estimate the pose of human upper body from a monocular video. A novel approach to locate the hands is proposed, which is designed to cope with the complicated situations such as short sleeves, fast motion and occlusion. Human silhouette and skin color blobs are extracted from the frames of the video; then candidate locations of head, hands, and elbows are chosen and evaluated by an inverse kinematics based strategy. Experiments demonstrate the efficacy and robustness of this approach. The algorithm is developed for a camera-based tennis game, in which poses of a player have to be estimated in real time (for avatar animation, action recognition, etc). It can also be applied in other human-computer interaction applications.
Augmented reality haptics system for dental surgical skills training BIBAFull-Text 97-98
  Phattanapon Rhienmora; Kugamoorthy Gajananan; Peter Haddawy; Matthew N. Dailey; Siriwan Suebnukarn
We have developed a virtual reality (VR) and an augmented reality (AR) dental training simulator utilizing a haptic device. The simulators utilize volumetric force feedback computation and real time modification of the volumetric data. They include a virtual mirror to facilitate indirect vision during a simulated operation. The AR environment allows students to practice surgery in correct postures by combining the 3D tooth and tool models with the real-world view and displaying the result through a video see-through head-mounted display (HMD). Preliminary results from an initial evaluation show that the system is a promising tool to supplement dental training and that there are advantages of the AR over the VR approach.
Real-time CSG rendering using fragment sort BIBAFull-Text 99-100
  Bo Peng; Kok-Lim Low; Thai-Duong Hoang
Constructive solid geometry (CSG) is a geometric representation where a complex 3D object is represented by combining simple solid objects (called primitives) using Boolean operators. The primitives can be convex or non-convex solids. The basic Boolean operations are union, intersection and subtraction.
Multi-resolution screen-space ambient occlusion BIBAFull-Text 101-102
  Thai-Duong Hoang; Kok-Lim Low
We present a new screen-space ambient occlusion algorithm (SSAO), which we call Multi-Resolution Screen-Space Ambient Occlusion (MSSAO). The method computes ambient occlusion by combining occlusion values using multiple mipmap levels of a g-buffer. Our method is based on the observation that occlusion due to further-away occluders are lower frequency and thus can be computed in coarser resolutions. On the other hand, nearby occluders cause higher-frequency occlusion that must be computed in finer resolutions. Our method samples occluders in screen space (similar to [Shanmugam and Arikan 2007]) and combines occlusion values across multiple image resolutions. Compared with two state-of-the-art SSAO methods [Filion and McNaughton 2008; Bavoil et al. 2008], results from our algorithm are closer to ray-traced results, even when our algorithm is running at comparable or higher frame rates. Because no random sampling is used, and occlusion values in all levels are combined using edge-preserving blending, our results are free of noise or excessive blurring which are common in other SSAO methods.

Interactions

Exploring the usability of immersive interactive storytelling BIBAFull-Text 103-110
  Jean-Luc Lugrin; Marc Cavazza; David Pizzi; Thurid Vogt; Elisabeth André
The Entertainment potential of Virtual Reality is yet to be fully realised. In recent years, this potential has been described through the Holodeck metaphor, without however addressing the issue of content creation and gameplay. Recent progress in Interactive Narrative technology makes it possible to envision immersive systems. Yet, little is known about the usability of such systems or which paradigms should be adopted for gameplay and interaction. We report user experiments carried out with a fully immersive Interactive Narrative system based on a CAVE-like system, which explore two interactivity paradigms for user involvement (Actor and Ghost). Our results confirm the potential of immersive Interactive Narratives in terms of performance but also of user acceptance.
The effect of DOF separation in 3D manipulation tasks with multi-touch displays BIBAFull-Text 111-118
  Anthony Martinet; Géry Casiez; Laurent Grisoni
Multi-touch displays represent a promising technology for the display and manipulation of data. While the manipulation of 2D data has been widely explored, 3D manipulation with multi-touch displays remains largely uncovered. Based on an analysis of the integration and separation of degrees of freedom, we propose a taxonomy for 3D manipulation techniques with multi-touch displays. Using that taxonomy, we introduce DS3 (Depth-Separated Screen Space), a new 3D manipulation technique based on the separation of translation and rotation. In a controlled experiment, we compare DS3 with Sticky Tools and Screen-Space. Results show that separating the control of translation and rotation significantly affects performance for 3D manipulation, with DS3 being at least 22% faster.
Industrial-strength painting with a virtual bristle brush BIBAFull-Text 119-126
  Stephen DiVerdi; Aravind Krishnaswamy; Sunil Hadap
Research in natural media painting has produced impressive images, but those results have not been adopted by commercial applications to date because of the heavy demands of industrial painting workflows. In this paper, we present a new 3D brush model with associated algorithms for stroke generation and bidirectional paint transfer that is suitable for professional use. Our model can reproduce arbitrary brush tip shapes and can be used to generate raster or vector output, none of which was possible in previous simulations. This is achieved by an efficient formulation of bristle behaviors as strand dynamics in a non-inertial reference frame. To demonstrate the robustness and flexibility of our approach, we have integrated our model into major commercial painting and vector editing applications and given it to professional artists to evaluate.
A creative try: composing weaving patterns by playing on a multi-input device BIBAFull-Text 127-130
  Jiahua Zhang; George Baciu; Shuang Liang; Cheng Liang
Woven fabrics are widely used in clothing because of their parallel and interlaced properties, which are formed by weaving. Creating a weaving pattern, especially hand weaving for interlacing yarns is a cumbersome task in the textile industry. In this paper, we propose two kinds of playing for creating weaving patterns on multi-input devices: the tie-up plan and the lift plan. Discrete notes on the treble staff are translated into signatures of treadling sequences and discrete notes in the bass staff are translated into signatures of theadling sequences. Artists can use their right hand to compose a treadling sequence for weft yarns and their left hand to play a threading sequence for warp yarns. The treadling and threading sequences become the notes on the full gamut of shafts and treadles. Our result shows that we are able to compose a family of weaving patterns in a similar way to playing the piano in a short time.
Dynamic decomposition and integration of degrees of freedom for 3-D positioning BIBAFull-Text 131-134
  Manuel Veit; Antonio Capobianco; Dominique Bechmann
In this paper we present a new interaction technique based on degrees of freedom (DoF) decomposition for accurate positioning in virtual reality environments. This technique (called DIOD for Decomposition and Integration Of Degrees of freedom) is based on an adaptation of the Two-Component Model. It provides two different control levels regarding DoF coordination, one integrating and one separating the manipulation of the DoF. Our hypothesis is that each control level is appropriated to a different phase of the positioning task. During the ballistic phase, users manipulate all the dimensions of the task at the same time. However, during the control phase, users try to manipulate specific dimensions individually. The results of a preliminary study we conducted seem to indicate that the DIOD technique is more efficient than existing techniques.
BioMetal glove BIBAFull-Text 135-138
  Masahiro Toyoura; Tatsuya Shono; Xiaoyang Mao
We propose a new haptic device for rendering contact sensation of virtual objects in camera-based Augmented Reality (AR) environments. Haptic feedback can help a user to intuitively sense virtual objects. For vision-impaired users, it also means a transfer from optical information observed in the cameras to haptic information. In our system, the contact between the virtual objects and the user's hand is detected with cameras. Therefore, when presenting the contact sensation, optical markers on the hand should not be occluded from the cameras so as to avoid disturbing the estimation of 3D position and posture of the hand. To fulfill such a requirement, we used BioMetal, a promising and versatile light and thin material that shrinks when electric current is applied, which provides the haptic feedback. Strings of BioMetal were stitched onto our proposed BioMetal glove. Because BioMetal does not shrink instantly when energized, a major challenge is how to deal with the time lag. We address this problem by setting buffering regions for pre-heating the BioMetal strings.
Influence of auditory and visual feedback for perceiving walking over bumps and holes in desktop VR BIBAFull-Text 139-142
  Luca Turchet; Maud Marchal; Anatole Lécuyer; Rolf Nordahl; Stefania Serafin
In this paper, we present an experiment whose goal is to investigate the role of sound and vision in the recognition of different surface profiles in a walking scenario. Fifteen subjects participated to two within-subjects experiments where they were asked to interact with a desktop system simulating bumps, holes and flat surfaces by means of audio, visual and audio-visual cues. Results of the first experiment show that participants are able to successfully identify the surface profiles provided through the proposed audio-visual techniques. Results of a second experiment in which conflictual audiovisual stimuli were presented, reveal that for some of the proposed visual effects the visual feedback is dominant on the auditory one, while for the others the role of dominance is inverted.

Rendering and visualization

Region-of-interest volumetric visual hull refinement BIBAFull-Text 143-150
  Daniel Knoblauch; Falko Kuester
This paper introduces a region-of-interest visual hull refinement technique, based on flexible voxel grids for volumetric visual hull reconstructions. Region-of-interest refinement is based on a multi-pass process, beginning with a focussed visual hull reconstruction, resulting in a first 3D approximation of the target, followed by a region-of-interest estimation, tasked with identifying features of interest, which in turn are used to locally refine the voxel grid and extract a higher-resolution surface representation for those regions. This approach is illustrated for the reconstruction of avatars for use in tele-immersion environments, where head and hand regions are of higher interest. To allow reproducability and direct comparison a publicly available data set for human visual hull reconstruction is used. This paper shows that region-of-interest reconstruction of the target is faster and visually comparable to higher resolution focused visual nhull reconstructions. This approach reduces the amount of data generated through the reconstruction, allowing faster post processing, as rendering or networking of the surface voxels. Reconstruction speeds support smooth interactions between the avatar and the virtual environment, while the improved resolution of its facial region and hands creates a higher-degree of immersion and potentially impacts the perception of body language, facial expressions and eye-to-eye contact.
Footprint-profile sweep surface: a flexible method for realtime generation and rendering of massive urban buildings BIBAFull-Text 151-158
  Cheng Liang; George Baciu; Jiahua Zhang; Eddie C. L. Chan; Guiqing Li
Generation of a large-scale city requires a significant amount of manual work and computation to process massive location information and model building geometry with multi-level of details. Normally, an urban city is heavily built-up with different architectural building patterns across extensively and topographically varied landscapes. In this paper, we introduce Footprint-Profile Sweep Surfaces (FPSS), a flexible and computationally efficient approach for realtime generation and rendering of massive urban buildings in a heavily built-up city. A solid constituting an urban building is represented as an instance of FPSS and is generated by sweeping a footprint along a profile with specific parameters. We present two forms of FPSS: super FPSS to address the shapes from architecture design and poly FPSS to address the shapes from imported GIS data. We make use of hardware tessellation to allow dynamic LOD according to view distance. A special scaling-translation-rotation displacement performed on the simplified profile is proposed to support detail generation. Experimental results show that realtime performance can be achieved using our approach to generate varied styles of urban buildings. Even inexperienced users are able to generate a building group quickly in their own style based on FPSS.
Automatic registration of multiple projectors on swept surfaces BIBAFull-Text 159-166
  Behzad Sajadi; Aditi Majumder
In this paper, we present the first method to geometrically register multiple projectors on a swept surface (e.g. a truncated dome) using a single uncalibrated camera without using any physical markers on the surface. Our method can even handle non-linear distortion in projectors common in compact setups where a short throw lens is mounted on each projector. Further, when the whole swept surface is not visible from a single camera view, we can register the projectors using multiple pan and tilted views of the same camera. Thus, our method scales well with different size and resolution of the display. Since we recover the 3D shape of the display, we can achieve registration that is correct from any arbitrary viewpoint appropriate for head-tracked single-user virtual reality systems. We can also achieve wallpapered registration more appropriate for multi-user collaborative explorations. Our method achieves sub-pixel accuracy and the image correction required to achieve the registration runs in real-time on the GPU.
   Swept surfaces are much more immersive than popular display shapes like planes, cylinders and CAVES. Our method opens up the possibility of using such immersive swept surfaces to create more immersive VR systems without compromising the simplicity of having a completely automated registration technique.
On-line visualization of underground structures using context features BIBAFull-Text 167-170
  Jiazhou Chen; Xavier Granier; Naiyang Lin; Qunsheng Peng
We introduce an on-line framework for the visualizing of underground structures that improves X-Ray vision and Focus and Context Rendering for Augmented Reality. Our approach does not require an accurate reconstruction of the 3D environment and runs on-line on modern hardwares. For these purposes, we extract characteristic features from video frames and create visual cues to reveal occlusion relationships. To enhance the perception of occluding order, the extracted features are either directly rendered, or used to create hybrid blending masks: we thus ensures that the resulting cues are clearly noticeable.
A multi-viewer tiled autostereoscopic virtual reality display BIBAFull-Text 171-174
  Robert Kooima; Andrew Prudhomme; Jurgen Schulze; Daniel Sandin; Thomas DeFanti
Recognizing the value of autostereoscopy for 3D displays in public contexts, we pursue the goal of large-scale, high-resolution, immersive virtual reality using lenticular displays. Our contributions include the scalable tiling of lenticular displays to large fields of view and the use of GPU image interleaving and application optimization for real-time performance. In this context, we examine several ways to improve group-viewing by combining user tracking with multi-view displays.

Poster session 2

A content-aware image resizing method with prominent object size adjusted BIBAFull-Text 175-176
  Meiling Shi; Lei Yang; Guoqin Peng; Dan Xu
A novel method that prominent object size can be controlled during image resizing is proposed in this paper. By a simple parameter adjustment, this new method can change the primary object size according to user preference. To accomplish this, we present a new quad distortion energy criterion by considering both the shape and the size of a quad. Moreover, we improve the single resolution visual attention model based on the rarity of features to a multiresolution saliency model. Then, redefine the significance map as the weighted average of this multi-resolution saliency result and gradient magnitude.
Implicit restricted quadtree based visualization of large scale terrain BIBAFull-Text 177-178
  Jie Zhang; Changwen Zheng; Pin Lv; Xiaohui Hu
Realistic rendering of large scale terrain scene in real-time is an important subject in virtual reality (VR) to construct a virtual environment with immersion and interactivity [Zhao 2009]. Large scale terrain scene visualization is popular in a variety of fields such as geographic information systems (GIS), military maneuvers, games, flight training and so on. Many visualization algorithms for terrain scenes have been proposed during the past decades, but to the authors' knowledge, approaches with high visual accuracy as well as low memory and time complexity have not been developed yet.
Evaluating virtual weights for haptically enabled online shopping BIBAFull-Text 179-180
  Yasser A. Bamarouf; Shamus P. Smith
Haptic feedback can help users achieve physically tangible interactions which could potentially improve electronic shopping. A set of haptic experiments were conducted to evaluate a number of thresholds for optimum discrimination across three sets of haptic weight ranges. Each set of the weight ranges (i.e. Low, Medium, and High) will have an optimum discrimination threshold for relative weight comparisons. Results showed that 20% provided optimum discrimination threshold for Medium weights (1.07N-1.75N), whereas High weights (1.92N-2.60N) need at least 10%. Moreover, 40% provided optimum discrimination threshold for Low weights (0.22N-0.90N). Also, 0% discrimination threshold accompanied by relatively higher thresholds (i.e. 30% and 40%) has improved its perception across all three sets of weight ranges but its optimal performance was at Low weight ranges. These results can be a foundation for designers of haptic applications to (i) use relative weights for products comparison with increased consistency and (ii) to identify the upper level constraints on the number of products that can be simultaneously compared on each set of weight ranges.
Closely coupled collaboration for search tasks BIBAFull-Text 181-182
  J. Simard; M. Ammi; M. Auvray
This article proposes to study the role of Collaborative Virtual Environments for the search of residues in molecular environments. This research highlights involved working strategies according the type and context of the task and shows some constraints and conflicting actions that may occur during closely coupled collaboration.

Human factors and collaborative virtual environments (part 1)

Simulating the local behaviour of small pedestrian groups BIBAFull-Text 183-190
  Ioannis Karamouzas; Mark Overmars
Recent advancements in local methods have significantly improved the collision avoidance behaviour of virtual characters. However, existing methods fail to take into account that in real-life pedestrians tend to walk in small groups, consisting mainly of pairs or triples of individuals. We present a novel approach to simulate the walking behaviour of such small groups. Our model describes how group members interact with each other, with other groups and individuals. We highlight the potential of our method through a wide range of test-case scenarios. A number of metrics are also proposed to quantitatively evaluate the quality of our proposed model.
A real-time visual attention model for predicting gaze point during first-person exploration of virtual environments BIBAFull-Text 191-198
  Sébastien Hillaire; Anatole Lécuyer; Tony Regia-Corte; Rémi Cozot; Jérome Royan; Gaspard Breton
This paper introduces a novel visual attention model to compute user's gaze position automatically, i.e. without using a gaze-tracking system. Our model is specifically designed for real-time first-person exploration of 3D virtual environments. It is the first model adapted to this context which can compute, in real-time, a continuous gaze point position instead of a set of 3D objects potentially observed by the user. To do so, contrary to previous models which use a mesh-based representation of visual objects, we introduce a representation based on surface-elements. Our model also simulates visual reflexes and the cognitive process which takes place in the brain such as the gaze behavior associated to first-person navigation in the virtual environment. Our visual attention model combines the bottom-up and top-down components to compute a continuous gaze point position on screen that hopefully matches the user's one. We have conducted an experiment to study and compare the performance of our method with a state-of-the-art approach. Our results are found significantly better with more than 100% of accuracy gained. This suggests that computing in realtime a gaze point in a 3D virtual environment is possible and is a valid approach as compared to object-based approaches.
Perceiving motion transitions in pedestrian crowds BIBAFull-Text 199-202
  Qin Gu; Chang Yun; Zhigang Deng
Perception of motion transitions in a pedestrian crowd is affected by many collective features such as crowd density, appearance variations, motion variations, and sub-group interaction patterns. We conducted a series of psychophysical experiments to investigate how these crowd features can influence human perception on walking motion transitions in a crowd when inexpensive motion blending algorithms are used. Our results provide useful implications and practical guidelines for performance-oriented crowd applications such as real-time games to improve the perceptual realism by effectively disguising motion transitions.

Human factors and collaborative virtual environments (part 2)

Heat diffusion based dynamic load balancing for distributed virtual environments BIBAFull-Text 203-210
  Yunhua Deng; Rynson W. H. Lau
Distributed virtual environments (DVEs) are becoming very popular in recent years, due to their application in online gaming and social networking. One of the main research problems in DVEs is on how to balance the workload when a lot of concurrent users are accessing it. There are a number of load balancing methods proposed to address this problem. However, they either spend too much time on optimizing the partitioning process and become too slow or emphasize on efficiency and the repartitioning process becomes too ineffective. In this paper, we propose a new dynamic load balancing approach for DVEs based on the heat diffusion approach which has been studied in other areas and proved to be very effective and efficient for dynamic load balancing. We have two main contributions. First, we propose an efficient cell selection scheme to identify and select appropriate cells for load migration. Second, we propose two heat diffusion based load balancing algorithms, local and global diffusion. Our results show that the new algorithms are both efficient and effective compared with some existing methods, and the global diffusion method performs the best.
Evaluating depth perception of photorealistic mixed reality visualizations for occluded objects in outdoor environments BIBAFull-Text 211-218
  Arindam Dey; Andrew Cunningham; Christian Sandor
Enabling users to accurately perceive the correct depth of occluded objects is one of the major challenges in user interfaces for Mixed Reality (MR). Therefore, several visualization techniques and user evaluations for this area have been published. Our research is focused on photorealistic X-ray type visualizations in outdoor environments. In this paper, we present an evaluation of depth perception in far-field distances through two photorealistic visualizations of occluded objects (X-ray and Melt) in the presence and absence of a depth cue. Our results show that the distance to occluded objects was underestimated in all tested conditions. This finding is curious, as it contradicts previously published results of other researchers. The Melt visualization coupled with a depth cue was the most accurate among all the experimental conditions.
Ensuring semantic spatial constraints in virtual environments using UML/OCL BIBAFull-Text 219-226
  Thanh-Hai Trinh; Ronan Querrec; Pierre De Loor; Pierre Chevaillier
Spatial objects and relationships between them, compose a spatial model that is the backbone of virtual environments (VEs). However, due to the natural complexity of both spatial objects and spatial information, the modeling of such spatial relationships is still a difficult task. This paper presents a novel approach for representing semantic spatial relations in VEs using the Unified Modeling Language (UML) and the Object Constraint Language (OCL). Our approach first uses the UML class model as a conceptual model for VEs. We then propose a spatial extension of OCL named VRX-OCL as a high-level and flexible language to cover multidimensional, manifold, and reference frame-dependent spatial constraints. We mainly focus on two important classes of spatial relations, namely, topological and projective relations that allow nonmetric representation of space. The applicability of our approach is demonstrated in the Virtual Physics Laboratory, a VE for learning physics. Based on the constraints satisfaction, the system is able to visualize abstract spatial information and thus provides educational assistance to the learners.
Reconfigurable tangible devices for 3D virtual object manipulation by single or multiple users BIBAFull-Text 227-230
  Laurent Aguerreche; Thierry Duval; Anatole Lécuyer
In this paper we introduce the concept of a Reconfigurable Tangible Device for manipulation of 3D objects in virtual environments by single or multiple users. This Reconfigurable Tangible Device (RTD) provides points of manipulation rigidly linked together. The shape of the RTD can be reconfigured at any time as its arms can be compressed or stretched by users at will. Due to its simple shape the Reconfigurable Tangible Device can be attached to any 3D virtual object. Then, it can fully define the motion of the virtual object in 6 Degrees of Freedom. Two examples of Reconfigurable Tangible Device were developed: one with three points of manipulation (a reconfigurable triangle) and one with four points. We illustrate how these two simple devices can match many different shapes of 3D objects, and in different contexts. Preliminary testing was conducted with the RTD based on three points of manipulation involving a collaborative manipulation task in virtual reality. It produced better subjective appreciation for the RTD compared to more classical 3D collaborative techniques.
Parallelizing continuum crowds BIBAFull-Text 231-234
  Tianlu Mao; Hao Jiang; Jian Li; Yanfeng Zhang; Shihong Xia; Zhaoqi Wang
In this paper, we present a novel parallelizing method for crowd simulators constructed with a continuum model rather than an agent-based model. The basic idea is to partition a crowded virtual environment into some districts, each of which keeps its own dynamic continuum fields and has several transitional blocks to make individuals keep continuum motion from one district to another. Our method makes continuum models to be parallelizable while preserving their existing superiority of generating smooth motion. Moreover, for most of large-scale applications, our partitioning method effectively simplifies the complexity of simulation. Experiments show that our method has achieved super-linear speedup and could employ more than one hundred worker processors to simulate 1 million people in an area of 672,400m².